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1986/87 merc 135hp s/n # OB243373

after a little looking
what is the difference between the 135 and 150

not sure if carbs are , or just jetting , looks like they offered 3 different carbs ??
also 3 different jet sizes

also are the heads a big difference from one piece to the two piece ?? will these bump up the compression ? if so about how much

Thanks

I think there is a differance in porting. The one and 2 piece heads have the same compression

Looking at parts book at mercruiserparts.com they do not show different parts for block , intake , or exhaust
I do see to look at parts notes, but that site does not show notes

are there any good outboard sites for complete parts books ??

I’m not sure if external links are allowed here. If they are not, please delete.

Some of these links your might know of, maybe a new 1 or 2?

Always has some good info and resources, especially if you post specific questions or use the search function.

http://www.screamandfly.com

There are motor specific threads that seemed to get frequented by many helpful users,
They also sell all sorts of boat related items including manuals.

http://forums.iboats.com/

A smaller tight knit group that is always active and always helpful. (real merc enthusiasts including some marine mechanics)

http://www.fastboatscanada.com


To have a shop manual solves many issues.
To spend a bit of time on the above sites can play HUGE rewards of knowledge also.

Personally I've always liked topic specific forums.

Always get to learn alot and meet others with like interests.