mercury 3 cyl 50hp & 60hp difference

[Owen]

Whilst searching for a map I came across the owners manual for my 1990 50hp 3 cyl merc.
I noticed that the bore & stroke are identical for both the 50hp & 60hp models. Doesn't say what the compression ratio is, so I'm curious if the extra HP is in the carbs.
I did a search on the net and found one post on a chat page that reckoned the only difference was the main jet (which I doubt).
Anyone have a service/parts manual?

Cheers,
Owen

[DNO40]

Owen.

It is true that the only difference may very well be just the jets. Had a similiar experience with mercury when purchasing outboards for the Vanuatu Police Force.


DNO

[Noelm]

probably a lot more than just jets, this has been discussed lots of times, there is usually too may items to change to make the difference in HP and it is not normally worthwhile, sure they share the same basic piston and block, but a lot of things are needed to get 20% more power.

[Noelm]

probably a lot more than just jets, this has been discussed lots of times, there is usually too may items to change to make the difference in HP and it is not normally worthwhile, sure they share the same basic piston and block, but a lot of things are needed to get 20% more power.

[Noelm]

wooops

[Owen]

That's why I'm looking for a service manual.
That way I can compare the critical parts.
If they share the same piston & cylinder sleeve, then that means the port timing is the same, so the only other places for the HP to come from is the carbs, ignition timing and head. 2 strokes don't respond well to high compression ratios (compared to 4 strokes) so I'm betting it's got the same head.
If I had to go to the trouble of finding new carbs I wouldn't worry about it, but if was as simple as a set of main jets, then why not? :)
If only I'd kept those Lectron flat slides I used to have ;D ;D

I once did a full port job on an old woolworths brand 2 stroke mower I had coz it was so gutless. Raised, the transfer ports, altered the piston port cutouts, the whole bit. I used to race two strokes, so I had all the formulaes to work out how to get the most out of it. Afterwards it would cut down trees, but used 4 tanks of fuel to do the lawn :-/ :-/ :-/

cheers,
Owen

[Noelm]

there can also be exhaust differences, manifold changes and they may have the smae piston size but they could be different as well as the block may be same size but ports can be disimilar, only part numbers can tell you (or and expoert)