# Yamaha F-150 -- Possible Blown Motor



## polar21 (Nov 5, 2007)

We have a 2004 F-150 with roughly 1,000 hrs on it. Coming across the bay on Saturday night and heard a loud boom and motor shuts down. Get towed back to the launch and it looks like one of the drive pulley's on the top of the motor came off the crankshaft gear, flew over to the drive gear and took a chunk out of it. From the time this happened to the time the motor shut down was approximately 15 seconds at the most. Do you think there is internal damage to the motor (valves hit the pistons, bent rod, etc)? When we took the cowling off there was no signs of catastrophic failure other than the drive pulleys (expected to see oil everywhere or a rod out the side of the block). We have ordered new drive pulleys and am going to put them on and do a compression test to see if we have any damage. 

What are my options if we need a rebuild/new powerhead? Can a machine shop do the block/head work and we reassemble? Should we order a new powerhead from Yamaha and bolt it on? Just trying to think through the options and see what is out there.


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## Mac1528 (Mar 24, 2012)

There's several power head rebuilders in the Pcola area. Have seen several threads about them. Do a search on power heads should get several hits to start you on your way if you need one. Hope it's just a a minor thing for you. 

Sent using tapatalk


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## Machine shop guy (Dec 19, 2008)

May can help. Call me Coastal Engine & machine. 850-433-7938


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## polar21 (Nov 5, 2007)

Here is a pic in case anyone was wondering what part broke:


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## Mac1528 (Mar 24, 2012)

So what's the verdict?


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## polar21 (Nov 5, 2007)

We wont know until we put the new parts on (two new gear pulleys, two smaller gears, and new belt). We will do a compression test, oil change, and fire it up. If it sounds like pennies in a coke can then its rebuild time (which absolutely sucks).


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## The Maintenance Shoppe (Nov 5, 2007)

Call Posner Marine, they should be able to answer your question.


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## murfpcola (Aug 28, 2012)

I am interested to hear the outcome. If it is an interference motor then I think you are looking at some valve damage at the least. I hope not for your sake.


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## X-Shark (Oct 3, 2007)

I can pretty much tell you what's gonna happen.

it's not going to turn.

F-150 Yamaha's are "Interference" motors....IE: Loose a timing belt and BAMN!

The valves just collided with the pistons.

Get your wallet Ready!


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## polar21 (Nov 5, 2007)

X-shark, do you think it got into the pistons as well? We are anticipating have to do a valve job, but was hoping to stop there and not have to do a complete rebuild. 

I still cant believe Yamaha would make a steel gear spin into an aluminum gear. That just seems like a recipe for disaster...(disaster for us!)


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## tiderider (Oct 1, 2007)

The "interference" is the non moving valves colliding with the still moving pistons. Best case is the pistons bent the valves without taking damage, but that does seem rather optimistic. You'll know when it comes apart for inspection.


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## X-Shark (Oct 3, 2007)

FYI: The 115Hp Yamaha's are the same way.




> X-shark, do you think it got into the pistons as well? We are anticipating have to do a valve job, but was hoping to stop there and not have to do a complete rebuild.


I like using this analogy when people ask questions like that.

I call it the "Watermelon Test".

"How many seeds are in a Watermelon?"

The answer is.......You don't know till you cut it open. The same applies to a lot of things.

You want someone to look into their crystal ball and tell you it will all be OK. That's just not going to happen.


And now you see another reason why I like Suzuki outboards. They have a timing chain that runs in a oil bath. No timing belt.


Long time ago I heard a story about a Honda that struck a submerged log.

It damaged the foot. That was bad enough, but the sudden impact and shock shucked the timing belt.....Yep same thing.....Valves into the pistons.


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## Snagged Line (Sep 30, 2007)

X-Shark;
I like using this analogy when people ask questions like that.
I call it the "Watermelon Test".
"How many seeds are in a Watermelon?"
The answer is.......You don't know till you cut it open. The same applies to a lot of things. [/QUOTE said:


> Bobby, that is a Great analogy. It seems Cold and uncaring at first, but it is Dead on. ( I might steal it from you.)
> 
> What is the likeliness of the rod bearings or wrist pins getting distorted from the strike???


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## polar21 (Nov 5, 2007)

If I had it my way I would like a timing chain and steel gears....


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## X-Shark (Oct 3, 2007)

> What is the likeliness of the rod bearings or wrist pins getting distorted from the strike???


Anything is possible, but a dent in the piston is likely.


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## Papajuju (Apr 18, 2014)

Kind of strange that I just saw a Yam F250 do this exact same thing.


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## speckledcroaker (Mar 23, 2012)

Wirelessly posted

Hello, I'm the guy that came over and bought the delta anchor from you, sorry to here this nice looking boat. A suggestion once yoe replace pulleys pull plugs and roll motor over by hand with valve cover off and check for valve bind it helps to pull valve cover that way you can see if you have any stuck valves. I dont really like to roll a suspect engine over till i know valve train is not binding. If you know somebody with a borescope and they know how to use it you can actually take a look at valves and piston top without teardown it helps. If it did bend a valve a head rebuild is pretty easy, minor dents in piston top can be blended and do not require a complete rebuild. Hope this helps. If you need some help give me a holler.


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## polar21 (Nov 5, 2007)

I am certainly interested in hearing more about "blending" a piston!


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## X-Shark (Oct 3, 2007)

> "blending" a piston!


It means you "Smooth" out the hard dent in the top of the piston. Light sanding disc.


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## polar21 (Nov 5, 2007)

I wanted to come back and update this thread and hopefully help anyone else out that might run in to this issue. The valves did hit the pistons, but the damage was very minimal and we still had decent compression on the motor. Pulled the head and two exhaust valves were bent. These were replaced and the motor was put back together including several new parts along the way (new timing belt, new fuel pumps, etc). I ran the boat yesterday and it performed very well. So a couple of months of fishing lost but we will be back on the water when this weather clears up. 

I would like to thank Shane Livingston and his partner in crime Chris for putting this thing back together as well as Todd from Coastal Machine in doing the head/valve work.


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## Emerald Ghost (Mar 11, 2008)

Good news Polar.
WHAT caused this in the first place ? Timing belt ?


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## polar21 (Nov 5, 2007)

I believe the source of the problem was that the cowling drains were clogged allowing "some" salt water on the back half of the motor. Over time this corroded one of the metal gears in the drive sprocket and ultimately led to its demise. On the F150's you have the crankshaft gear and two sprocket gears that drive the two camshafts. When one of the sprockets broke, the end result was similar to what would happen if a timing belt broke. 

All in all I am glad its back together!


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## floater1 (Oct 31, 2007)

Thanks it was nice meeting you


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