‘85 Yamaha V4 115 rebuild

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,308
So, a few questions and some advice needed...

the time has come for me to eventually dig in and make a start on rebuilding my recently acquired classic boat project and engine. Engine is as stated and briefly I’ll state that the reason for rebuild is that it took in water contaminated 2 stroke oil from its feed tank. The engine apparently stopped working then seized. All I knew of it when buying the boat. I’ve managed to free it off but knew something was wrong when turning by hand soaked in oil. Took the heads off each V and one unit has serious damage to piston and scoring on bore. Signs of water in all other bores but not bad. 0 compression in the bad one. The others have no visible damage to pistons but slight and tiny marking on bores.
Decided to rebuild whole power head and just about to acquire the parts. Very expensive here in the uk and over £1000 for parts.
I have seen a kit on eBay in America for around $500 and about $ postage. Thinking of going for it.

Now...this is the first time I have rebuilt an outboard engine and looking forward to it, but it’s unfamiliar to me in parts. I’ve rebuild a Yamaha jet ski revently but was apparently simpler.

Questions are;

when orderimg the kit, there are options on the over size of pistons. Would the general advice be to get the largest and bore and hone to suit, given the serious damage to one of the units at least ?

also, the really badly damaged unit had all sorts of play in its travel and movement and has slightly came into contact with the head. Is there a chance the crank may be damaged or perhaps just the bottom end ?

anyhring else I should do or look out for whilst it’s in bits ?

finally I don’t suppose any of you guys know where I could get a rebuild kit cheaper ?

thanks all
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,874
I do not think Yamaha has rebuild kits,
is the kit aftermarket?

water/bad oil or no oil to me would mean damage to lower end not just piston and cylinders
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Sounds like the age and poor condition of this motor could make it a good candidate for a mooring anchor....
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,269
Take it apart.-----Inspect all parts before spending money.-----Might consider taking gearcase apart for inspection too.-----Be a shame to rebuild the powerhead only to find the lower unit also needs major work.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,308
Thanks guys. Appreciate it.

The gear box and everything else, but the motor internals are in amazingly good condition.
I agree I now just need to strip it down as suggested, before spending any money.

Thanks again.
 
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