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2007 Yamaha 15hp (F15CPLH) - worth saving or part it out?

T

ts258

New member
I have a 2007 Yamaha 15hp (F15CPLH) that needs some work and I'm trying to determine if it's worth saving. The motor ran smooth last season but upon bringing it into a local shop for winter service, they informed me that the lower unit was shot and compression was low on the motor so it wasn't worth servicing. They returned the motor with the lower unit (or most of the lower unit) in pieces. I found the compression comment surprising as the engine ran smooth the prior season. As for the shifting, it never felt brand new but it shifted fine.

Compression
I first tested the compression on each cylinder as a starting point. Unfortunately each cylinder came back reading 50psi (+/- 1). That said, upon further research, I've read that to get an accurate compression reading, the motor needs to be run for a while in order to get warm. (1) Any truth to this? Additionally, it is important to note that this motor has done a lot of idling and slower trolling so I'm suspicious about carbon buildup on the valves, preventing a proper seal. Again, the engine was very smooth when running last season. Lastly, I put a camera down each cylinder to see if there was anything noticeable and I did see some pitting on the cylinder walls (see pictures).

https://imgur.com/a/JeaHOhC

Lower Unit
Upon inspecting the lower unit parts returned to me, the majority of them are there and they seem to be in usable condition. I'm fine with reassembling the lower unit but I am unsure about what shim size needs to be used. I believe I have the shims for the drive shaft pinion but I am not seeing the shims for the propeller shaft. I've looked at the service manual but I do not see anything around shim specs, nor is anything printed on the lower unit casing (that I can see). (2) Anyone have any guidance here?

I am trying to determine - should i attempt to rebuild the lower unit, purchase a rebuilt one off of ebay for $650, or just part out what's left of it and move on to another motor?
 
With the lower unit removed connect a hose to the water pump transfer tube. You can then start and run the motor. To get it hot for a compression test.

Best to do a compression check with the motor hot but not essential. When you did your test was the throttle in the wide open position?
 
You can also do a differential pressure test. Aka leak down test. It will tell you the source of any leak areas. i.e. gasket, valves, rings, etc..
 
Very helpful questions, boscoe... thank you!

So following your advice, I hooked up a hose to the motor, sans lower unit and fired it up. It started up easily and I let it run for 10 mins until the block heated up. I then pulled the plugs and ran another compression test with throttle wide open (did not do this when testing cold). This one resulted in much better readings - 155 psi for the top and 153 psi for the bottom. I believe the engine is worth saving.

As for the service manual, I believe I was looking at the owners manual rather than the service manual so I will need to purchase that and wait for it to arrive. My thought here is -- if all of the primary components are original and I'm missing just the shims, I should be okay just ordering them based on the original spec listed in the service manual rather than doing measurements myself. I say this as I understand to do this properly, you need some expensive tools which I'm not ready to invest in at the moment. Thoughts on this approach?
 
Tooth contact is used for shimming.----Time consuming but no special tools required.----And rattle that shop for any missing parts.----Find another shop as well.
 
T
ts258 said:
Very helpful questions, boscoe... thank you!

So following your advice, I hooked up a hose to the motor, sans lower unit and fired it up. It started up easily and I let it run for 10 mins until the block heated up. I then pulled the plugs and ran another compression test with throttle wide open (did not do this when testing cold). This one resulted in much better readings - 155 psi for the top and 153 psi for the bottom. I believe the engine is worth saving.

As for the service manual, I believe I was looking at the owners manual rather than the service manual so I will need to purchase that and wait for it to arrive. My thought here is -- if all of the primary components are original and I'm missing just the shims, I should be okay just ordering them based on the original spec listed in the service manual rather than doing measurements myself. I say this as I understand to do this properly, you need some expensive tools which I'm not ready to invest in at the moment. Thoughts on this approach?
Click to expand...
The service manual will have a procedure to determine the shims that need to be used. I will provide you with a snippet from the SM tomorrow afternoon. You will then use a dial indicator to verify the back lash is within specifications.
 
Hi boscoe -- I would love to take you up on that offer! I ordered what I thought was the service manual which finally arrived after almost a month of waiting, only to find out that it was the owners manual, not the service manual. Any chance you can post the snippet from the service manual? I really appreciate the help!
 
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