[jimbobo]

i have a c85trls -, found #3 sparkplug was not firing had small amount of rust on it. motor ran bad, i was told on this forum to pull head and go from there. i did, all cylinders look good (smooth bore) lots of corrosion in water passages. cant tell by visually looking if head is warped or not. do i need to go to machine shop ? i see what looks like small cracks around combustion chamber (around bottom of sparkplugs) but a friend says they look like casting flaws, is this possible? also removed plate that is bolted to head with water jackets, it is also corroded. i need to change that gasket also but dont know what you call it. any reply is appreciated

[99yam40]

look up your motor at a parts web site, here is one but you can look anywhere you want to find the name of parts on your motor.

http://www.boats.net/parts/search/Ya...ard/parts.html

You can take the head and plate to a machine shop or you can mill them your self with a piece of wet sand paper layed on a flat smooth surface like glass or plexiglass. Just move in a figure 8 motion with light even pressure keeping water on the sand paper will keep it working without plugging up the paper longer.
Cracks are not a good thing on heads. Was it on the #3 cylinder where you said the plug had rust? And did the head chambers all look real clean or did some have carbon on them and only #3 was cleaned off? That would indicate a cracked head and leaking water into the cylinder.

[jimbobo]

all had slight carbon build-up. just came back from ordering new gaskets. mechanic said head looked good/gasket was questionable. he thinks i might have water in fuel.at this point i will put it back together and attempt to drain fuel. i did notice my primer bulb does not stay hard after i pump it a few times but motor still ran good (before i noticed water on plug) is it possible i have a leak in fuel line somewhere and if it is laying some water it is getting in that way? thanks for your reply- jim

[99yam40]

I realy do not believe you could get water into the cylinder and on the plug by way of your fuel. Water in the fuel will cause plugging in filters,carbs or other parts but it normaly does not flow through the jets and such very well.
Do all of the cylinders have good compresson?
Usually I would check that before pulling apart just to see how far to go into a motor.
You said #3 was not firing, does that mean it was not getting spark or it was getting spark but not firing when you checked by pull the plug wire when it was running?
I would pull and clean carbs and filters if ypou have not done so already

[jimbobo]

sorry i didnt say thanks sooner. i still have the problem. i changed head gasket, it is not warped compression is 90 psi on all 3. i am still getting water in cylinder. just got a response today saying to check exhaust gasket. i am assuming that is the plate with the 22 bolts,with the inner and outer gaskets. some one else said to check where the powerhead connects to the exhaust, which i wasnt prepared to pull powerhead but would if i knew that was the problem. whats your opinion?

[99yam40]

I have not seen a motor that was getting water into a cylinder that was not washed clean of the carbon in that cylinder.
Have you drained or pulled the carbs to check for water in the bowls?
I know I stated it was not probable but if the bowl is full of water on one carb it might be able to suck water through main jet and into cylinder at higher RPM's while running on other cylinders.
Are you getting spark on #3 and just not firing?

[rodbolt]

we have seen ex gasket failures and pin holes corroded in the ex divider plate cause the same issues.
its an easter egg hunt, I hate it but sometimes thats just what it is.