1986 90hp body compatible with 1987 110hp Power Block?

[bscappell]

it looks like the difference between the 90hp and 110hp in that the 110 has a bubbleback and the 90 has a flat back. is that correct? does this make them incompatible?

http://www.maxrules.com/fixomcrph2.html

 

[emdsapmgr]

Re: 1986 90hp body compatible with 1987 110hp Power Block?

Not sure what you mean by incompatible. Are you trying to swap parts between them or swap powerheads? I see you may be looking at buying a rebuild powerhead. The biggest difference between the two engines are the exhaust, block intake/exhaust porting, heads and the size of the carb throats.

 

[bscappell]

Re: 1986 90hp body compatible with 1987 110hp Power Block?

Not sure what you mean by incompatible. Are you trying to swap parts between them or swap powerheads? I see you may be looking at buying a rebuild powerhead. The biggest difference between the two engines are the exhaust, block intake/exhaust porting, heads and the size of the carb throats.

i am looking at replacing the blown 90hp power head with the 110hp power head. I understand that i will need to swap carbs and such too. just concerned with the 110 power block (or long block so to speak) mating up with the 90hp mid and lower unit.

 

[wired247]

Re: 1986 90hp body compatible with 1987 110hp Power Block?

Same thing. It will bolt right up. A few internal porting differences but thats all. You might want to rejet your carbs to that years 110 specs but it all depends on the 90 carbs and what venturi/throttle plate sizing they had that year. Your 90's carbs might or might not be the same as the 110 carbs.l

 

[bscappell]

Re: 1986 90hp body compatible with 1987 110hp Power Block?

Same thing. It will bolt right up. A few internal porting differences but thats all. You might want to rejet your carbs to that years 110 specs but it all depends on the 90 carbs and what venturi/throttle plate sizing they had that year. Your 90's carbs might or might not be the same as the 110 carbs.l

So what if I use the whole power block from the 110 carbs and all to mount to the 90 horse mid and lower unit? The 110hp motor does not have functioning tilt trim, the 90hp does.

 

[emdsapmgr]

Re: 1986 90hp body compatible with 1987 110hp Power Block?

The 110 carbs are larger than those on the 90. You won't get the performance out of the 110 block with the 90 carbs. Also, possible that they may not supply enough fuel to keep that powehead cool at WOT. If you swap for the 110, be sure the 110 carbs are on it.

 

[bscappell]

Re: 1986 90hp body compatible with 1987 110hp Power Block?

The 110 carbs are larger than those on the 90. You won't get the performance out of the 110 block with the 90 carbs. Also, possible that they may not supply enough fuel to keep that powehead cool at WOT. If you swap for the 110, be sure the 110 carbs are on it.

yeah i never planned on using a smaller carb for a bigger motor.

Back to the original question. the 110hp exhaust is a bubble back. the current 90hp is a flatback. will the bubbleback mate with the flat back ?

 

[wired247]

Re: 1986 90hp body compatible with 1987 110hp Power Block?

The 110 carbs are larger than those on the 90. You won't get the performance out of the 110 block with the 90 carbs. Also, possible that they may not supply enough fuel to keep that powehead cool at WOT. If you swap for the 110, be sure the 110 carbs are on it.

Not the case at all. Ive got a few sets of factory 90HP carbs in the shop with 1 5/16" throttle bores. Same carbs and close to the same jetting as the 140 spec engines. OMC was all over the place with carbs. If they are larger than 1 3/16" they can be jetted to work on the 110.

 

[emdsapmgr]

Re: 1986 90hp body compatible with 1987 110hp Power Block?

The bubble back (110/115) crossflow powerheads are made at the factory with special exhaust filler blocks bolted into the exhaust chest. Once they are bolted in place, the factory machines (decks) the exhaust face completely flat on a mill. You can swap these blocks over onto your 90, but still will need to have the block decked prior to bolting the exhaust manifolds (covers) in place. If your 90 carbs are the same throat size as those on the 110 and you are comfortable rejetting them, that will work. If you are unfamiliar with jetting outboard carbs, just run the 110 carbs. My 96 90 hp crossflow has 1 3/16" carbs..

 

[wired247]

Re: 1986 90hp body compatible with 1987 110hp Power Block?

You dont need to install the fillers. You can use the bubble back without the fillers or you can even use the flat back on the 110 block. Either will work about the same. You probably wont notice a difference if you install the filler blocks.


He doesnt have to jet anything by "scientific means". Just look up the engine that he is using and jet the carbs accordingly according to that engines specs. If he has oddball carbs like 1 3/16" on a 90 then he can find something close enough. FWIW my '81 90 had rubber intake stuffers, 1 5/16" carbs with 65 main jetting.