Help! Blown head gasket

Walter1904

Let’s go!
Sep 2, 2018
5
0
29
San Diego
Name
Walt
Boat
19ft bayliner
Hey guys I’m getting desperate with fishing being so good and lobster season beginning.
I have a 2005 Yamaha 115 on my boat and it’s definitely got a blown head gasket (water in oil) and it’s going to cost a fortune to get it looked at. It also has a possibility of having a bad cylinder or a warped head and all the motor work is beyond my knowledge.
To buy a new used motor or fix this thing..
Does anyone know a decent mechanic with great rates? Any advice?
Cheers!
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skipjack

I've posted enough I should edit this section
Oct 20, 2004
1,041
366
66
santa maria
Name
skip
Boat
2320 Parker "Donna Marie"
You probably have a bad thermostat,very common.
The water is from condensation in the crankcase from running too cool.
If it still runs fine this is your problem.
If it runs bad like a bad head gasket,you will need to tear it down.
 

Walter1904

Let’s go!
Sep 2, 2018
5
0
29
San Diego
Name
Walt
Boat
19ft bayliner
You probably have a bad thermostat,very common.
The water is from condensation in the crankcase from running too cool.
If it still runs fine this is your problem.
If it runs bad like a bad head gasket,you will need to tear it down.
Yeah it runs bad
 

KneppNasty

Snappin’ necks & cashin’ checks....
Sep 10, 2017
282
192
34
Seal Beach, CA
Name
Jeramy
Boat
Trophy 2509
I have a 2009 Mercury 90HP 4-stroke (Powerhead made by Yamaha) that was basically doing the same thing as yours - water in engine oil, low compression in 3rd cylinder, running rough and eventually became difficult to start the motor.

After exhaustive research trying to find any and all options for replacing the head gasket and having the head surfaces honed (tasks beyond my own personal skillset).....I eventually found that I could buy an entire compatible 115HP powerhead (same powerhead as a 90HP) on eBay for $1500.00 shipped with low hours, confirmed good compression in all (4) cylinders, and 30 days no questions asked warranty.

I ended up building a ghetto come-along lift to pull off the old powerhead and pop on the replacement all by myself without any assistance required. Changed over all of the electrical harnesses and other various components.....and after that it fired right up and runs perfectly now with zero issues whatsoever!
Like a brand new motor for less than $2k spent in parts (plus my own time/labor, of course!)

Hope my recent experience might be able to help you out in some way, shape, or form!

-Jeramy

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gecsr1

28' Aquasport "Reel Adventure II"
Jul 15, 2005
14,063
3,569
Poway Ca
Name
Gary
Boat
28' Aquasport "Reel Adventure II" / PlainJaneRods
Ian Johnston excellent mobile mechanic.. Mercury & Yamaha
if you want his number PM me.
 
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IN2DEEP

I've posted enough I should edit this section
Jul 4, 2006
270
17
Torrance
Name
Scott
Boat
22' Cuddy Bayrunner 115 Fourstroke Merc
I had the same issue with my 2002 115 Merc 4 stroke (Yamaha powerhead) last fall.
17 years old, about 2000 hrs.
Searching the internet, I found a couple posts of repairs that were made but no detail of the repair.
I'll post what I did successfully and what you might be up against in the repair.
This issue seems to be common on saltwater, inline Yamahas after around 10 years of age.
To start off, I am not a motor mechanic, I am a machinist and very used to disassembling machinery and reassembling them to repair them.

Once the head was removed. I saw how and where the water was getting into the oil supply. The head started getting corrosion under the gasket and eventually it will loose compression on that cylinder and/or leak cooling water into the crankcase oil. Hopefully you loose compression before the oil starts getting diluted with cooling water.

Once I cleaned the gasket off the block mating surface. I saw that the surface was free of corrosion and did not require any repair

I decided to leave the valves/springs/retainers installed and seated.
Cams and shims etc. were removed in order and set aside.
I plugged up any hole that chips or grit can get into.

I proceeded to grind out all the cancerous aluminum to be welded and built back up.
There were several spots that needed to be welded

End of part 1
 

IN2DEEP

I've posted enough I should edit this section
Jul 4, 2006
270
17
Torrance
Name
Scott
Boat
22' Cuddy Bayrunner 115 Fourstroke Merc
Part 2


Resurfacing the welded head went well. I got away cleaning up the surface at -.005-.008 thousands.
I had to clear to weld from the water channels after the resurface.

I cleaned up the machined head, purchased a new head gasket, zincs and finally got around to replacing the timing belt that I've been putting off.
Reassembled everything and it's been good for the last 10 months.

If you've gotten this far, I have a good tip for you.
Be sure to keep up with changing the internal zincs anodes so they keep doing their job.
These are 17 years old

Well, there you go.
Now there is a detailed repair that is searchable on the internet
Scott