Yamaha f115 head gasket blew-need to replace cylinder head?

[dsteding]

Re: Yamaha f115 head gasket blew-need to replace cylinder head?

An update, we're thinking it is the surface on the exhaust guide above the oil pan, if you look at the bottom of the sealing surface of this picture, you'll see some black corrosion and it is rough to the touch:

The same surface is on the right side of this picture:

The gasket from that location has some corrosion on it too, see the bottom of this pic:

But, the oil pan itself looks fine, see it in the background here:

We're at close to $3000 in terms of repairs, we're debating whether the exhaust guide needs to be replaced. Part of me thinks it could reseal if cleaned and using sealant, part of me wants to put a new one in because I don't want to spend the labor costs involved to get at it again.

 

[rodbolt]

Re: Yamaha f115 head gasket blew-need to replace cylinder head?

dunno, nothing really jumps out at me.
use NO sealents on any rubber parts unless specifically recommended by the service manual.
if you must use a sealent on the metal gaskets,even though its not really reccomended, then a product like BRP/OMC gel seal II or its locktite equivalent will work ok.
use a scotch lock pad or its equivalent to clean the gasket surfaces then use a straight edge and a .003" feeler guage to check surface flatness.
myself I would have removed the powerhead with the cyl head still installed and made a plate to pressure test the cooling system and would do it before reinstalling the powerhead.

 

[dsteding]

Re: Yamaha f115 head gasket blew-need to replace cylinder head?

use a scotch lock pad or its equivalent to clean the gasket surfaces then use a straight edge and a .003" feeler guage to check surface flatness.
myself I would have removed the powerhead with the cyl head still installed and made a plate to pressure test the cooling system and would do it before reinstalling the powerhead.

If it is flat, is there any reason to put a new exhaust guide in?

Agreed re plate and pressure testing, that would have been a bit more of a efficient way to do it, in retrospect.

 

[rodbolt]

Re: Yamaha f115 head gasket blew-need to replace cylinder head?

a reason to replace the exhaust guide I dont see, however pictures are not as good as real life which isnt anywhere near as good as simply using a dye penatrant to check for cracks or pinholes.
the kit is about 25 dollars and is a two part spray. one is a dye/penatrant the other is a developer.
works great to find cracks and pinholes.
use the old base gasket as a template, dont worry about the holes fwd of the crankshaft, drill the mounting holes in a piece of 3/8ths or 1/2 AL plate.
drill 1 hole in the center of the exhaust outlet about 1/4.dril 1 1/4 hole in 1 oil retrurn passage
drill and tap 1 hole in the plate water inlet to the block. I would tap it 1/4 NPT.
use a leakdown tester or equivalent and apply air at about 30 PSI.
leakage above 0% indicates a leak.

if it leaks use soapy dishwashing liquid and find out where its coming from.
what the attempt is to isolate what part of the syatem is leaking.
have the combustion chambers,valveseat areas been dye cheked for cracks?
your on an expensive easter egg hunt.
try to stack the odds of finding the golden egg in your favor.

 

[AGENT 37]

Re: Yamaha f115 head gasket blew-need to replace cylinder head?

$3000 is a very pricey easter egg hunt.....

I didn't get near that much into my project. I was actually looking into getting a different motor before I fixed mine. I ended up with a good motor and put under $1000 into it. I ran my rebuilt power head on the F80 (it was actually the cowling that was from a F75) parts for 54 hours without any problems. I sold the motor last summer along with the boat.

My oil pan looked perfect but still leaked. I'd also leak test the oil pan separate from the power head. If you have corrosion in one spot it is usually all over the inside. The pan can get corroded from the outside in as well as getting corroded from the inside out through the cooling and exhaust passages. I was amazed when I figured it out. I believe that may have been the problem to begin with and not the cyl-head that I had welded and milled. It is certainly not cheap or fun to troubleshoot water in the lube system.

 

[dsteding]

Re: Yamaha f115 head gasket blew-need to replace cylinder head?

$3000 is a very pricey easter egg hunt.....

I didn't get near that much into my project. I was actually looking into getting a different motor before I fixed mine. I ended up with a good motor and put under $1000 into it. I ran my rebuilt power head on the F80 (it was actually the cowling that was from a F75) parts for 54 hours without any problems. I sold the motor last summer along with the boat.

My oil pan looked perfect but still leaked. I'd also leak test the oil pan separate from the power head. If you have corrosion in one spot it is usually all over the inside. The pan can get corroded from the outside in as well as getting corroded from the inside out through the cooling and exhaust passages. I was amazed when I figured it out. I believe that may have been the problem to begin with and not the cyl-head that I had welded and milled. It is certainly not cheap or fun to troubleshoot water in the lube system.

Yes, I agree. The $3k would be all in, diagnosis, tearing this down, and replacing the exhaust guide and the oil pan. Which I'm kinda inclined to do if I had some assurance that this motor would work at the end of the day.

Rodbolt, I'll talk to them about using a dye penatrant on the pan, and see if they can pressure test the whole assembly. I was thinking the same thing about the feeler gauge and a straight edge in terms of testing that one suspect surface.

 

[dsteding]

Re: Yamaha f115 head gasket blew-need to replace cylinder head?

Screw it. I'm repowering.