# Boat will plane for a couple minutes then slow down



## tyminer

OK, this has riddled me for a while now, it starts and idles great. Move out past the no wake zone and put the hammer down. I hops up on plane fine and goes for a few hundred yards then slows down and then will only go about 10 mph WOT. If i bring the throttle back down and then throttle up again, it will try for a second to bring up enough power to raise the bow then it will lose power again. It will still idle and start fine just not enough power to get it on plane after the initial short lived success.

The motor is an old 1974 johnson 70hp 3cyl. - I have replace all three coils and rectifier. I emptyied the old gas from last year and put in 10 gal of fresh gas/oil. I also replaced the entire primer bulb and hose assembly. The carbs have been gone through several times. Yesterday when we tried it out i noticed that even though it bogged down, all three carbs were spraying plenty of fuel. So i dont think its a carb/fuel pump kind of problem. 

I beleive its electrical. To back up this idea is the many spark plugs i have gone through trying to get this thing going over the last year. All 3 are always kinda wet with oil/fuel when i check them, even with only 10-15 minutes of runtime on a fresh set. I do know the little coil packs on the startor are cracked and have leaked the gel stuff out of them. But its my understanding that the stator is just to provide enough power to run the engine and charge the batteries. I know it puts out some power because the voltage goes up on my fish finder as it runs. 

My thoughts are that its either the stator, the timer base or the powerpack. The problem is that i dont really know enough about them to determine which one(s) is causing the problem, and these parts are kinda expensive and non-returnable. I do have a repair manual but i dont have some of the expensive test equipment to properly test them.

Anyways, i just wanted to see if any of you had some suggestions.

Thanks


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## John Becker

maybe a clogged fuel filter?


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## BIGRIGZ

From my limited experience, it sounds like the power-pack.

The way you tell it: I would suspect a fuel issue first but, if you are sure that the floats in the carbs are working and the fuel line isn't losing pressure, and the fuel filter/screen isn't clogged, may be the Power-pack



Next, as far as I understand it, the Power-pack controls the engine under a load. So it would explain how the boat runs fine at idle and then when you try to run it up on a plane, the Power-pack may not be working and causing the problem.



My power pack was about $75 bucks and I followed every step in the manual; for my motor it basically said test the coil, test the stator, test the rectifier if everything checked out okay and the problem still persists change the power pack. so I did and it fixed my problem.



btw, do you have good enough compression, have you checked compression?



hope the forum is able to help you, post up the results either way!!


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## BIGRIGZ

> *John Becker (5/18/2009)*maybe a clogged fuel filter?




That was my first thought too.... check that screen/fuel filter under the hood on the engine....


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## tyminer

> *BIGRIGZ (5/18/2009)*From my limited experience, it sounds like the power-pack.
> The way you tell it: I would suspect a fuel issue first but, if you are sure that the floats in the carbs are working and the fuel line isn't losing pressure, and the fuel filter/screen isn't clogged, may be the Power-pack
> 
> Next, as far as I understand it, the Power-pack controls the engine under a load. So it would explain how the boat runs fine at idle and then when you try to run it up on a plane, the Power-pack may not be working and causing the problem.
> 
> My power pack was about $75 bucks and I followed every step in the manual; for my motor it basically said test the coil, test the stator, test the rectifier if everything checked out okay and the problem still persists change the power pack. so I did and it fixed my problem.
> 
> btw, do you have good enough compression, have you checked compression?
> 
> hope the forum is able to help you, post up the results either way!!


I checked the filter on the fuel pump and it was fine. The carbs are spraying plently of fuel through thechamber so i dont think its fuel related.

I checked the compression last year, when it was still having the same problem and they were all at about 125.

I hope its just the power pack, that would definetly be the easiest and cheapest fix of all the old remaining electrical components.


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## BIGRIGZ

another thing I thought of;



check the coils make sure that they are getting a sufficient ground.



some coils ground through the mounting bolts, make sure the coils are getting a good ground.


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## John Becker

just in case, check the fuel filter direction. Just sounds too much like a fuel issue to me. If the filter is on backwards, it will idle correctly but die under load.



Sorry if I'm stuck at the fuel issue, just everything in my head is screaming "not enough fuel".


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## kks

check the vent on the gastank make sure its not clogged, if it is one of the portable tanks check the screw vent on the gas cap make sure it is open.


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## PMac

The symptoms you describe also perfectly fit a bad "pump up" fuel bulb. Those pump up bulbs have check valves in them and occassionally one will break loose. At low fuel flow it works fine but under acceleration it will stall. OMC had a series of bad bulbs a few years back. Try bypassing the bulb...


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## tyminer

I will check the grounds to the coils.

I'll double check the fuel filter but i think it is correct. I even took the pump apart yesterday to make sure none of the diaprams have a hole. Everything looked fine even checked the fuel lines to the carbs for leaks, etc.

The tank is an 18 gallon one thats mounted above deck and the vent is a bare hose (about 1/2" i.d.) with no check valve or anything.

The carbs spray plently of fuel and the plugs are always wet, so it seems to me that the ignition isn't strong enough to burn the fuel, but im no expert


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## tyminer

> *PMac (5/18/2009)*The symptoms you describe also perfectly fit a bad "pump up" fuel bulb. Those pump up bulbs have check valves in them and occassionally one will break loose. At low fuel flow it works fine but under acceleration it will stall. OMC had a series of bad bulbs a few years back. Try bypassing the bulb...


I haven't tried bypassing the fuel bulb but it is a complete new assembly. It stays pretty firm. Also, when experiencing my problem.....pumping the bulb doesn't help.


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## tyminer

I checked the ground to the coils and they are ok.

One thing i noticed is that sometime last year i replaced the rectifier, and i had a wire hooked up wrong. Its the one with a red wire and two yellow wires. The red goes to 12v and one of the yellow wires goes to the stator for power or something, the other yellow one is not supposed to be connected (just there as a backup for the connected one if it blows), but it was connected ............somehow the extra wirewas connected to the tach wire coming from the stator at theterminal block:doh. So.....since (if i understand correctly) a rectifier is basically just a diode then i was sending 12v to my tach lead from the stator which i believe puts out AC current.

I have put the wires where they should be and will go try here in a bit to test it. I doubt this is my problem but since it may have been sending 12v to my TACH output, it could have been heating things up or throwing off the stator or something.

I hope this makes sense. Its hard to explain something that I dont fully understand (meaing im no expert on recitifers or stators, lol.)


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## Flounderpounder

To eliminate any potential fuel line problems, try running it on agas canoff a short (new) line. I had a similar problem once, tried the above trick, and it ran great. Turned out to be a collapsing fuel line (interior liningcreated a "flapper valve" that would close with increased suction). You could be correct that it is electrical, but this is a good way (virtually free) to be sure it's not a fuel delivery problem. My boat ran great almost to WOT, then would crap out. Drove me nuts for a while! Good luck!


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## GULFFISHER1

I had the same problem last year. Loose ground strap.


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## 69Viking

I had a Larson Cabrio with a 5.0 L Volvo engine that had the same problem. It would get up on plane and just seemed to bog down and then wouldn't have enough power at full throttle to get back on plan. If I let the engine cool then it would get on plane again for a while before bogging down again. 

I took it to the dealer several times while still under warranty and they couldn't find the problem. Finally I hammered the dealer enough that they had a Volvo rep fly down here and meet me at the marina to work on my boat. Before even leaving the dock he has me start the engine and listens for a while and then tells me to shut it down. He tells me it sounds like my timing is off. He gets his tools out and checks the timing and sure enough it's off, probably been that way since new at the factory. He adjusts the timing to the correct parameters and we go for a test run, it runs better than it ever has and the problem never came back. 

If you haven't had the timing checked I would get that done. It's a pretty quick and easy thing to check with the right tools and know how.


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## BIGRIGZ

I suppose it's possible that he got the plug wires mixed up coming from the coils but, I doubt it......



that would make it run idle ie; on 2 of the 3 cylinders = not enough power to plane out.....



makes you go hmmmmmmm, I feel his frustration. Been there done that!


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## tyminer

Well i took it out to try again to see if the rectifier was causing the prioblem and it isn't.

I checked the grounds earlier and they seem fine.

Haven't checked the timing, guess that could be it.

Guessim just gonna have to bite the bullet and take it to the shop.

Thanks for all your input guys!


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## devildog83

could your choke linkage be loose? 



causing it to pull the choke closed at high RPM and bog it down?


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## DOUBLE "D" & LV

what RPM is the engine running when it will not go but 10 MPH?


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## tyminer

> *devildog83 (5/18/2009)*could your choke linkage be loose?
> 
> causing it to pull the choke closed at high RPM and bog it down?


No, i checked and the choke valves are completely open when it happens.


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## tyminer

> *DOUBLE "D" & LV (5/18/2009)*what RPM is the engine running when it will not go but 10 MPH?


I can't honestly answer this because I dont have a tach. I would estimate it to be around 2000 rpm and the 10 mpg is my best guess.


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## DOUBLE "D" & LV

Does your warning horn work? You could be overheating and the motor goes into reduction mode and you do not know because the warning horn does not sound. I cannot remember if that had the reduction mode or not. If you look at the powerpack and see a tan wire going into it, it has reduction mode.


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## tyminer

I have tested the buzzer manually applying power to it, but im not certain that the temp sensor works.

The power pack calls for a brown wire but not a tan one, I will have to check my manual to see where the brown wire goes.


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## Sea Monkey

The OLE motor with a gremlin.

I've got a friend that has the same motor and about the same year. He has the same problem with his. He has yet to find the gremlin. You gotta love being a boat owner, always something to figure out. Why does this do this when it should do that, etc. I have spent many of miles walking around in circles while scrathing my head trying to find a gremlin in my motor. I feel your frustration.


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## BIGRIGZ

Is there any chance that the trigger wires to the coils got flip-flopped some how?



ie; trigger wire for #1, #2, #3 transposed???? 



#1 hooked to #2, and #2 hooked to #1


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## tyminer

> *BIGRIGZ (5/19/2009)*Is there any chance that the trigger wires to the coils got flip-flopped some how?
> 
> ie; trigger wire for #1, #2, #3 transposed????
> 
> #1 hooked to #2, and #2 hooked to #1


At this point anything is possible, I did replace all three coils last year. Would it still idle and run low speed like a champ?


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## MR

New fuel blends wreck havoc on older fuel pumps. Evin/Johnson have newer fuel pumps that have diaphragms made of rubber compounds compatible with ethanol fuels. This happened on an early 90's evinrude 200hp. Replaced the fuel pump and all was well. The new fuel either puts small holes in the rubber diaphragm or reduces its elasticity to the point where it does not pump efficiently.



My take on it since you have replaced everything else.


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## tyminer

Well i took it out this weekend, it noticed the bottom carb not putting out quite as much fuel as the others, so to check it out further i pulled the carb and opened the bowl, dammit the gasket was falling apart inside the bowl, breaking loose and clogging it and probably the other two carbs as well. Now im pissed cause i just rebuilt those carbs last fall. The only thing i can think of is that damn ethanol fuel. Not sure about the ethanol situation in pensacola but the gas stations here in oklahoma city are using ethanol less and less, I see more signs everyday of stations advertising 100% gas.

To add insult to injury the helicoil for my middle cylinder is starting to strip out. How in the hell can i fix that? could i jb weld the helicoil threads to the head?

Sincerely,
A frustrated boat owner :reallycrying


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## rongarrett

Let me say first that I think the 3 cylinder omc engines were the best they ever made. I used to race that engine in the SST 60 class and my motor lived at 8000 rpm as a normal day. I now run a 70 hp 1982 Evinrude.

Generally speaking if an ignition problem exists, it will show up at all rpms. there are exceptions, but................ Fuel problems however can show upin just about all situations. Lots of folks tear into the ignition system when they actually have fuel problems.

You need to be anal when rebuilding carbs. Use anly genuine OMC parts. I buy my engine parts directly from an OMC dealer. I don't trust internet suppliers. How would you tell if those gaskets were rated for E-10 or not? Make sure you replace the needle and the seat when rebuilding the carb. Make sure the float is adjusted so that the float is perpindicular to the carb body when flipped upside down. Don't tighten the needle seat anything more than good and snug so as not to distort the seat. Replace all gaskets from the kit that fit your carb. Oh, yea, buy the complete kit, not just individual parts. It will be money well spent. either rebuild or replace that fuel pump. When the diaphragm starts to go it will drive you nuts, causing any number of bad things to happen.

As an example I'll tell you a little war story. I got my motor as part of a project boat I bought. It was bolted to a home made wooden 2X4 motor stand. No way to run it, just came with the boat package. Motor cover was in bad shape. The prop looked like someone had taken a chainsaw to it. Had what looked like new spark plugs. I hooked everything up and it cranked first try. Didn't idle very well. Checked the lower unit oil, whoops, milky. I took it to the local Evinrude dealer as I no longer had the proper puller from my racing days. some one had replaced the water pump impeller, but ignored all the lower unit seals, which were all leaking. Cost: 325.00 which included installing a helicoil for a stripped out bolt.

Above work did not improve idle {of course}. Took spark plugs out. They were in fact new, but the top one was missing the compression gasket. New plugs helped idle some. Noticed that motor was running way cool, could put my hand on head immediately after shutting down. Took thermostat cover off. Whoops, thermostat and bypass valves missing completely. Replaced all. Knowing that this condition will casue excessive carbon buildup, I removed the spark plugs and sprayed the tops of the pistons with Deep Creep, {made by Seafoam}. Did this two or three times a day for three days. Filled the cylinders full of the Deep Creep. Lo and behold black syrupy looking stuff began running out of the exhaust. I also installed a 20 micron exterior fuelfilter/water seperatorand poured a full can of Seafoam into six gallons of gas. {Note: always turn the motorover with the spark plugs removed to get rid of any liquid in the cylinder before intalling new plugs.}Idle got a little better, but still not right. It would idle for long periods, but after sitting for only five minutes, you would have to race the motor for awhile to get it to catch. Rebuilt all three carbs. There were new parts in all of them, but I found the idle jet on the bottom carb stopped up. This motor does not have adjustable jets. Idle better, but still lacking a little. Bit the bullet and rebuilt the fuel pump, also replaced all the fuel lines, using the special tie wraps for the smaller lines. Wallah, now idles like it should. Cranks better than any outboard I have ever owned. Runs full throttle without missing a beat. {knock on wood}. 

Sorry for the long post, but I hope the story helps someone with similar problems. Be anal if you make repairs yourself. Buy, read, and memorize your motor from a FACTORY manual. This motor is simply constructed. In my experience simple is always better in salt water, which is a harsh environment. Also you are much more likely to do needed repairs if you can do them yourself, rather than wait in line at the boat dealer. Use the best oil money can buy. There is a difference. Run either Seafoam, or StarTron at all times to recommended conscentrations. And finally, change that filter/water seperator each season whether you think it needs it or not. Oh yeah, studies have shown the best maintenance for an outboard is to put them in the water and run them at least once a month.


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## tyminer

Thanks for the post, I'll be ordering parts in the next few days.

Does anyone know if "jb weld" will be ok on my stripped spark plug helicoil? or anyone have a better suggestion?


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## rongarrett

I don't think JB weld will do the trick. I would be afraid it would go at precisely the worst time. Spark plugs screw into the head cover. I would just replace that cover? {the actual head is another part.} I wouldn't think it is too expensive. I'd go have a look and see how much they are?


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## rongarrett

Note: concerning my above suggestion to run Seafoam as an additive. I no longer will use Seafoam. I think StarTron will be the way to go.


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## tyminer

Its Fixed!!!!!!!!!!!!!!!!!!! :clap

I got my carb kits today and when i pulled off the carbs I noticed some stuff in the reed box for the #3 cylinder, come to find out some of the foam on the inside of the engine shroud got sucked in. :looser I carefully retrieved the foriegn material, rebuilt the carbs, installed them and headed to the lake for a test. Hot damn, ran around for about 2 hours and it never missed a beat. I asume if i would have tested the compression I might had noticed something was wrong with the #3 cylinder but the i probably would of thought.....damn, time for a new motor, lol

Thanks for all your help guys, I've definetly learned alot through this process.:bowdown


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## Pass Time

helicoils are easy to replace. they are almost like a spring that winds into a larger threaded hole. You shoild be able to get a helicoil tool for a few bucks and just emove the old one and install a new one. I esed to do this on my dirt bike years ago


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