# 5.0 I/O Mercruiser steam from PCV



## Stumpease

Had a problem over the weekend with engine stall at idle. During engine flush I removed the spark arrestor to adjust idle and noticed a small amount of steam coming from the right bank PCV tube and some condensate on the arrestor. Probably what was causing the low speed stall.

First thing I thought was a head gasket was going/gone but a buddy told me it could just as easily be an exhaust gasket or leak between the wet exhaust and head somewhere.

Does anyone have any suggestions or maybe more importantly, can anyone recommend a good marine mechanic. I've tried three here in the Milton area and have have horrible results.


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## TheCaptKen

You have water in the oil and it is steaming out. Usually due to rusted out risers or manifolds leaking water back into the engine. Is your engine oil tan in color?


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## Stumpease

Definitely tan in color. Looks like boating season is over early for me....

Now I need a good mech in the Milton area preferably. 

Any suggestions?


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## Stumpease

Re-thinking it.. After some research looks like it won't be too hard to change out the risers, manifolds and gaskets myself. I'll try to take some pics as I go.

Any suggestions would be helpful :thumbup:


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## SHO-NUFF

ebasicpower.com

Best prices on manifolds and risers. 
I assume its a raw water cooled engine, and you will need both mans and risers. Its not difficult task, IF you can get the manifold bolts out of the head. Sometimes the bolt heads are rusted away. Like CaptKen said, it appears you have water intrusion via an exhaust valve from a faulty manifold or riser. Don't let the engine set up for to long with out running it or you will end up with much worse problems!


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## Stumpease

Talked to a mech today who said there was no way it could be exhaust manifolds or risers. If water is in the oil I either have a cracked block or blown head gasket....

Really bummed right now.

OK, I'm over it. Now I need to find another mech for a second opinion. Please, if anyone has a trusted mechanic, pass on the name. The guy I talked to today came from this CL posting:

http://pensacola.craigslist.org/boa/3790247226.html

Anyone knows anything about him?


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## Stumpease

SHO-NUFF said:


> ebasicpower.com
> 
> Best prices on manifolds and risers.
> 
> 
> Thanks for the Link btw, that place has amazing prices!


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## TheCaptKen

Unless your boat visited the cold north this past winter, it didn't crack. Plus if it was cracked, it would have filled the crankcase full of water in just a short time. Just a mechanic trying to make a mountain out of a mole hill.


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## Stumpease

Progress so far:

Got a call from Davlar Marine, I've seen good things about him on this forum. He said it was most likely mani/riser problem and gave me some good tips on how to find out. 

I disconnected two hoses from the riser and ran them into the bilge. Changed the oil and filter, and cranked the engine. It ran smooth but I noticed water spewing from the risers so I cut it off and found two more hoses going into the manifolds from the bottom. By the time I noticed it the water had already made it into the crankcase. So I changed the oil and filter again, disconnected the other two hoses and ran it again. 

I'm letting it cool down now before running it one more time and changing the oil/filter. I expect to see some milky oil because it had pooled on top of the heads, but not near as much as before... unless it's a cracked block. I really don't think it is though because I think I would have way more water in the crankcase. 

I'll update after the next oils change.


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## Stumpease

5 oil changes and finally seeing something that looks like oil when I change it, Long day.

Gonna order new manifolds, risers and boots. if it isn't the problem, I'll need em with a new block anyway.


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## Stumpease

Old manifolds and risers off. Very suprised at how easy they were to remove. Certain the bolts were not torqued to spec. Only had a problem with one head rounded off but was able to hammer a 13mm onto it and off it came.

Gaskets looked to be in pretty good shape but several of the ports were blocked with rust.


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## Stumpease

Wasn't the manifolds or risers...


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## SHO-NUFF

Bummer.
Time for a tear-down and inspection.
I would start by removing the intake manifold. Inspect the intake gaskets for failure and the water passages in the intake itself and each ends of the heads. A tell-tale sign will be rust or corrosion around the water ports and in the lifter galley under the intake.. Look for cracks or seepage in the block an inch or so above the valve lifter bores at cylinders 2,4,5 and 7 . This is a common area for the block to freeze crack. If the intake is aluminum, check the gasket surface areas around the water ports. They are prone to corrosion on a raw or "salt" water cooled engine. Does not take much to cause a leak. Tap the area around the water ports with a ball peen hammer or similar to insure integrity. 

If that is not the problem, pull both heads. There are 17 head bolts in each head. So find them all. Take the heads to a machine shop and have them pressure tested and magnafluxed. Also inspect the head gaskets and block surfaces around the water passage areas, though I doubt this is the problem unless it was ran really hot before you started having problems.The head gaskets should be stainless steel in a marine application. 

If the heads check good, and no obvious signs of head gasket failure, its time for a block. 
To save a ton of money, you already have new manifolds and risers, have your old heads machined and purchase a short 
block from Autozone or the likes. There is absolutely no difference between a 5.0 Chevy MercCruiser and a 5.0 {305 c.i.} out of a 1980 Chevy truck or car with one exception. You have to use brass freeze plugs and stainless steel head gaskets in a marine application. So you have to change 8 freeze plugs from steel to brass for about 15 bucks, that's it, considering it is a standard rotation, single engine boat. You could opt for a 5.7 {350} long block also. The 305 heads will fit, but will have too much compression for 87 octane fuel because of the small combustion chamber size. 
If you plan on keeping the boat, go ahead and replace the Gimble bearing in the outdrive while the engine is out. Easy time to do it.:thumbup:


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## Stumpease

SHO-NUFF - You just made my day! Started tearing it down yesterday, wrenched my back in the process but got all of the new parts off. Intake and carb are next.

Can't believe how supportive the wife is being... Always a good sign.


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## Machine shop guy

If you need some advice. Please feel free to give us a call. Coastal Engine& Machine inc. 850-433-7938


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## Stumpease

Kudo's to Coastal Engine & Machine!

Found a hole in the intake manifold. I should be back on the water by next weekend!


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## SHO-NUFF

Stumpease said:


> Kudo's to Coastal Engine & Machine!
> 
> Found a hole in the intake manifold. I should be back on the water by next weekend! . . . . . . . . . . . . . . . . . . . . . . . . . . .
> Todd at coastal is a good guy! Glad it was an easy fix.


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## Machine shop guy

Thank you! Stuck my pocket knife right through it! Just like Butter! Amazing!:thumbsup:


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## Stumpease

An update for those interested. Todd found the hole and worked my heads so they are ready to go back on. Zero luck finding a 2bbl intake for this engine. Sandblasted the hole and it ended up being about 3" x .5". Cut and installed a patch from the bottom then JB welded the inside and outside seams. Looks good but I still want to find a new one, aftermarket or otherwise.

Waiting on some parts now, new water pump and a bunch of gaskets. They will be here 01JUL and I should have it back together by the 4th. 

Todd, I'll be calling for the valve lashing


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## SHO-NUFF

There are adapters that allow you to mount a 2bbl carb on a 4bbl intake.


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## Stumpease

SHO-NUFF said:


> There are adapters that allow you to mount a 2bbl carb on a 4bbl intake.


Any idea where I can get one? I've looked at all of the online marine parts places and can't seem to find it.


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## Snagged Line

Was the Hole directly under the Thermostat in the bottom of the manifold?? 

That is where mine rusted out letting water drip into the crankcase. Todd and Coastal Engine & Machine rebuilt my 5.0 Mercruiser and discovered the bad Intake manifold... They did a great job on the Rebuild...


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## Stumpease

Yeah, right under the thermostat housing. Todd knew right where to look.


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## Stumpease

Just finished torquing the left side head bolts and think I may have put the right head on the left side. Everything appears to line up exactly. Is this a bad thing?


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## GWally

Stumpease said:


> Just finished torquing the left side head bolts and think I may have put the right head on the left side. Everything appears to line up exactly. Is this a bad thing?


I'm going from memory, like over 30 years ago when I was messing with heads and intakes on a small block chevy. The heads only work one way. The intake valves and openings have to be to the inside, exhaust to the outside. I seem to remember that the holes for the intake manifold were rectangular, exhaust may have been round, not sure.


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## Stumpease

Appreciate the answer GWally, but I think I may have asked the question wrong. The exhaust and intake ports are correctly oriented the way I have it.

Imagine sitting in front of the engine, if you take the left cylinder head, rotate it 180 degrees it will fit onto the right side of the block. The only thing that I can tell is different is the front water jackets on the heads were more corroded that the back, probably because the intake blocks off the rear water jackets. 

What I'm reading on other forums is that they can be switched. Just want to be sure before I torque both sides and waste two head gaskets...


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## Stumpease

Well, now I see one difference, the accessory mounting holes (power steering pump, fuel water separator) are different. Think I just wasted a head gasket....


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## Snagged Line

When it comes time to bolt on the exhaust manifolds I suggest you make some Guide pins. Take two bolts about an inch and a half longer than your manifold bolts and cut the heads off w/ hacksaw. Thread them one in each end of the head and snug them with vice grips. then slide exhaust gaskets over the long bolts to hold them in position and then do the same with the exhaust manifold. It will help keep everything in place without fighting the weight of the manifold. Start the rest of the bolts and snug them down. Then remove the Guide pins with vice grips and install last two bolts and then torque them...... Good luck with the rest of your repairs... keep up the reports...


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## Stumpease

That was one of the first things I did Snagged. I had a back injury when I started this process so while I was figuring out how I was gonna get the 40lb exhaust manifolds off I came up with the guide pin idea. Worked like a charm, in fact, they are now part of my toolbox!

I just switched the heads, absolutely no difference at all, except for a wasted head gasket...


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## Stumpease

Almost there! A little concerned about the distributor... seems to be a lot of play in the rotor...


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## Snagged Line

I feel your pain _Stumpease, You have the additional burden of handling heavy stuff in tight a space.... I went through what you are doing back in March..._
_What do you mean by Play in the rotor? It might be worth pulling the _distributor _back out and inspecting everything..._


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## Stumpease

Well, finished putting her together today. Started rough but smoothed out after turning the distributor some. let it run for awhile to get it up to temp before hooking up a timing light. My timing mark is jumping around, 5-7 degrees either way. Ran it up to about 1600rpm and still had the same jumping around. Didn't sound like it was missing or running rough. Can't figure out what would cause the mark to jump. Makes setting the timing impossible.

Any suggestions?


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## SHO-NUFF

Check for excessive timing chain wear or stretch, assuming this is a clockwise from the front rotation engine. To do this, remove the distributor cap so you can see the rotor button. Place a 5/8 inch socket and breaker bar on the crank shaft balancer bolt. Turn the engine slowly clockwise until the rotor button moves, then counterclockwise until it moves the opposite direction while noting how far the crankshaft turns before the rotor button actually moves. There will be some "slop" but it should not be excessive, like a quarter turn of the crank without the rotor button moving. 

If the chain checks out good, you have a distributor advance problem. GM used several different marine distributors over the years.
Is there a vacuum hose attached to the distributor? If so, disconnect the vacuum hose and try to set the timing again. If it does not have a vacuum advance, you need to inspect the mechanical advance weights, the weight pivot holes and the advance weight springs. A broken spring will cause erratic timing. Some distributors have the advance weights under the rotor button while others are located under the advance plate where either the points or pickup coil is located. If located under the advance plate you will need to pull the distributor, and drive out the roll pin that holds the drive gear on the distributor shaft. The shaft will come out of the distributor housing, along with the advance plate and reveal the weights and springs.

Not really that difficult to do, 
Good Luck!:thumbup:


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## bonita dan

Boats don't use vacuum advance. What ignition system ya got..points,thunderbolt? An engine serial # would be helpful too. :thumbup:


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## SHO-NUFF

bonita dan said:


> Boats don't use vacuum advance. What ignition system ya got..points,thunderbolt? An engine serial # would be helpful too. :thumbup:


Not from the factory, but have seen many early HEI distributors with vacuum advance dropped in to convert from points. They don't meet Coast Guard requirements for marine use in an enclosed engine bay, but its a common and potentially dangerous swap. 

You are correct, as the OP has not posted any info on the year model. I would just about bet its a Prestolite or Mallory distributor. And if using old school breaker points, improper gap, dwell or a faulty condenser can cause erratic timing as well.


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## Stumpease

The year model is around 87, no vacuum advance, thunderbolt ignition. From what I've read, there is a wire I need to jump to get the timing mark to settle down. Just waiting for the rain to clear so I can get back on it. No real slop in the chain using the socket on the crankshaft pulley method. 

I was able to take it out for a spin on the 4th and it ran good, better than before this all happened and no more water in the oil!


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## SHO-NUFF

Stumpease said:


> The year model is around 87, no vacuum advance, thunderbolt ignition. From what I've read, there is a wire I need to jump to get the timing mark to settle down. Just waiting for the rain to clear so I can get back on it. No real slop in the chain using the socket on the crankshaft pulley method.
> 
> I was able to take it out for a spin on the 4th and it ran good, better than before this all happened and no more water in the oil!


Determine weather you have the Thunderbolt IV or V system first. The IV will have the ignition amplifier module mounted on the exhaust riser elbow. The V will be mounted on the distributor.

Nothing special to do for setting timing on the IV system. Just time at 8 degrees BTC. The V system will have a purple and white extra wire at the module not hooked to anything with a butt connector on it. This wire needs to be grounded with a jumper to set the initial timing. 
Being around an 87 model, you probably have the Thunderbolt IV system, so no jumper required. Make sure the black ground wire from the module is not corroded and has a good ground connection.


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## Stumpease

It must be a V because there is nothing mounted on the riser. 

Still haven't had a chance to get back on it. Had a question though before I do. Is the block casting number the same as the serial number? The casting number on the block is 14093627. It was located in the same place as the serial number is shown on my manual but it doesn't really match any of the serial numbers that I have seen online...


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## SHO-NUFF

The casting number you listed is for a 1987-93 305 engine with a roller cam and one piece real main seal.
The serial number MIGHT be stamped on a boss on the engine block right below the head on the starboard side of the engine. And the numbers could not mean a thing because they could be GM numbers. 
Manufactures such as Merc-Cruiser, Crusader, OMC-Cobra and so on buy engines from GM to modify for marine use. 

Most of the time, there is a decal attached to one of the valve covers or the plastic engine cover mounted above the carb, that could be long gone, that list the model and serial number of the engine as well as specifications for timing, firing order and idle speed.
As far as the ignition. If it has an extra purple and white wire, its a V series Thunderbolt. If not then its the IV or earlier model. The timing advance, for a total of 28 degrees is all done by the ignition amplifier based on engine RPM. There is no mechanical advance. Inspect every connector for corrosion and make sure the grounds are good.


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## Stumpease

the saga continues....

Took her out Saturday, left from Archie Glover headed to Quietwater to watch the air show. Everything seemed fine till about 20 minutes into the trip when I heard a clunk. Immediately idled down and open the engine compartment. No noises at idle but as soon as I applied throttle (about 1100rpm) I could hear what sounded like maybe a collapsed lifter?? I was already at the 3 mile bridge so I limped the rest of the way. 

Checked oils and fluids, all good. Spent a few hours there, cranked her back up with no problem but when I gave her gas, the noises from the engine were awful. Idled back to Archie Glover, (8mph = 2.5hrs) and took her home. 

Pulled off the valve covers and saw a couple of the rocker arms were oriented in such a manner that made me think I may have put them onto the wrong studs. When I took them off, I kept them together by cylinder but not by valve so I had a 50/50 chance of getting it wrong. Contemplated switching the ones that looked skewed but decided it was probably best to replace them all along with new lifters and rods.

This time I will use a half turn on the valve lash vice the one full turn listed in the book. 

If anyone (Todd?) has any other suggestions, I am open to all 

Thanks for all the great suggestions you have provided to date!


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## Machine shop guy

Call me! Do not change lifters!!! Rocker arms do not need to be in order


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## Stumpease

Can't find your card Todd. Sent a PM


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## specktackler57

A+ what captken said.BE CAREFULL.make sure your mechanic is trust worthy and ask for references.


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## Stumpease

Machine shop guy said:


> Call me! Do not change lifters!!! Rocker arms do not need to be in order


Found your number but you were already gone for the day. I'll hit you up in the morning.


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## Machine shop guy

K....


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## Stumpease

Todd,

Been working 10 hour days so haven't been able to do much let alone get the boat down to ya.

I have all of the parts I talked about, push rods, lifters, rocker arms and gaskets and I want to try to get on there today to at least change out the rods and rockers since I have them. 

Opened the boxes today and they sent roller rockers instead of the OEM ones I ordered. Is there anything different with the installation of roller over OEM? 

I'm gonna follow the manual to the tee with the exception of 1/2 vice one full turn for the lash adjustment. Anything else I should look for?


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## Stumpease

OK, finally a decent day to get back on it. Thanks again to Todd at Coastal Engine and Machine for everything.

Removed the old lifters and rods. Found a bent rod on #5 intake. One of the intake manifold bolts was hitting it... apparently I neglected to reinstall one of the lifting eyes while installing the intake, that extra 3/16" of thread allowed the bolt to strike the rod. I knew I left it off, but had no idea it would result in a bent rod.

All of the new rockers and rods are installed but that is as far as I got tonight. 1/4 turn on the lash this time too. Should be able to button it up tomorrow and see how she runs. Hopefully the bent rod did not do damage to anything else....

Thanks for reading


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## Snagged Line

I have my fingers crossed for a good outcome......


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## Stumpease

Buttoned her up, cranked up as soon as I turned the key! 

That's when the new noise started  

Sounds bad, rod or main bearing is my guess but I need an expert now.

Todd, I want to bring it by sometime this week, let me know when is a good time. I can't take any time off work so it would be at lunchtime. It's a 23' deckboat and I haven't seen a place to park it over there.

Let me know


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## Stumpease

How about a mobile mechanic, can anyone recommend a good one?


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## Stumpease

OK, had someone from Davlor come by and look at the engine to diagnose the noise. May have been David but I'm not sure, the wife said the guy was clean cut, personable and went right to work.

After cranking it he removed a couple of the plug wires one by one until he isolated the offending cylinder. His prognosis: rebuild... apparently the water in the oil was there long enough to screw up the crank and connecting rod bearings.

David, if you read this, I want to throw some of this work your way but money is getting tight. I can take off all of the ancillary parts (out drive, manifolds and risers, wiring and distributor) if you can get it out of the boat and over to Todd at Coastal for the rebuild. I'll then need you to bench test and put it back in. 

Todd, if you are reading this, is there any chance you have a 5.0 short block that you can just swap out for mine?


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## Snagged Line

Take a Crapload of pictures of EVERYTHING and mark every wire and log where it came from along with every sensor, Hose and linkage.... When you go to put it back in, You will still wish you had taken more pictures and better notes....................


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## Machine shop guy

I'm looking for something I can put together for you! Thanks


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## Machine shop guy

Found something. Call me please. Need to ask you a few questions Dave! Thanks


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## Stumpease

Todd,

This is attached to the mains in my old block. Do I need it?


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## SHO-NUFF

Stumpease said:


> Todd,
> 
> This is attached to the mains in my old block. Do I need it?


Its called a "Windage Tray" and you need it if the oil pan itself does not have a baffle. Its purpose is to prevent the oil from sloshing or foaming caused by the crankshaft rotation at high speeds, so the oil pump pickup does not suck air and starve the engine for oil. If the new engine does not have main bolts that have studs for mounting, use the main bolts out of the old engine, cleaned, oiled and properly torqued to specs. 70ft/lbs.


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## Stumpease

Thanks Sho-Nuff, exactly what Todd told me. 

Engine is back in the boat, have the exhaust and outdrive to install. Working 12 hour days again so time is short but I should have her ready for a test fire on Saturday.

Any recommendations for break-in?


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## Stumpease

And the saga continues.....

Got her all put together on Saturday, double checked all connections and clamps and fired her up. Set timing with a POS light that wouldn't light half the time but she sounded and felt good!

Took it out at around noon with just me and my son. Idled out to the main part of the Blackwater and hit the throttle to about half, slowly, got right up on plane and felt great. Went down the river varying the throttle position every minute or so. Turned around at the I10 bridge and took her up to about 2/3rds throttle, around 3600 rpm (WOT is 4200). At 3600 my throttle was all the way forward. Figured I had the wrong prop on (14.5x19p) stopped and changed to a 14.5x17p and saw no difference in RPM's

Ecstatic that it felt so smooth and shit that I invited the family for a short cruise the next day. 7 adults on the boat and I couldn't get 2200 rpm out of it. Wasted no time getting her back on the trailer.

At the house I first looked for a leaking intake or carb gasket, found nothing. On the hose, not in gear I can get all the RPM's I want. Didn't try it in gear yet but will tonight.

If I get no RPM's in gear then I will assume it is an outdrive problem although when I put the outdrive back on and spun the prop the shaft turned with no resistance so I do not expect to find any issue there. 

Edit: no loss of RPM's on the hose with prop engaged...

Maybe a timing issue? Fuel issue? all suggestions welcome.

To refresh everyone's memory, its a 23' deck boat with a 5.0 I/O Mercruiser freshly rebuilt....


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## Sea Monkey

Wirelessly posted

The OLE Making You Earn It!!

I feel for you after all you have been thru with the rebuild. Sounds alot like me when I decided to become a Mercruiser mechanic. Sounds like you may be having fuel problems, my(224ci 4cyl) motor would reach WOT rpm while running on the hose (Ido not recommend one do that) however while the boat was is the water it would not reach the WOT rpm. My problem was the fuel filter. I have a water seperator filter. I would definately set the timing with a light if you have not. I have run my rebuilt Mercruiser in Black Water river many of times.

"GET'EM OFF THE BOTTOM"


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## Stumpease

OK, this will be my final entry on this post, hopefully.

Put the new block back in the boat a few weeks ago, took it out for the day and it ran great. Until it broke...

Took the whole motor back to Todd at Coastal. He took it apart and found that #3&4 rod bearings were toast and so was the crank. Here is why;

When assembling the engine I noticed the oil pickup tube was welded to the pump. Since both pumps bore the same numbers I just swapped the bottoms. Not a good idea. the clearances were not the same and the pump gears wore into the bottom causing shavings to infiltrate the motor. Also, I used the Corry Station hobby shop to rinse everything off before assembly. Based on the condition of the solvents in their tanks I probably introduced more debris than I cleaned.

Todd rebuilt me again! This time he put together every part that oil would touch. I'm waiting on a new intake manifold and thermostat housing to arrive so I can put it back together and lift it back in. 

I am really thinking about switching to a closed cooling system too based on the fact that this originated from a corroded water jacket on the intake. Anyone have an opinion on that?


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## Machine shop guy

Mark, I'd love for you to come visit us again without your engine on the trailer! Just you buddy with a happy face would make my day!  I believe we're in good shape!


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