compatibility 100hp to 115 powerheads

[cdoliver]

Will a powerhead from a 1979 115hp johnson fit onto a 1979 100hp johnson lower unit. And can I use all of the electrical and carbs from my 100hp? I have a bad 100hp powerhead and I found a 115 for cheap ready to go. Thanks for your answer.

 

[iwombat]

Re: compatibility 100hp to 115 powerheads

Same powerhead, I think the only difference is the intake filler blocks. Have fun with the swap.

 

[cdoliver]

Re: compatibility 100hp to 115 powerheads

Thanks for that info. Can you educate me on what to/not to do with the intake filler blocks on the 115 powerhead when i make the conversion? do I use the one from the 100hp or leave it as is? Thanks again

 

[iwombat]

Re: compatibility 100hp to 115 powerheads

If you're using the carbs from the 100, I'd just swap everything from the intake out. DHadley would be much more informed about what all you can and can not do. Lacking the specifics, I'd keep the 100 intake and carb setup in tact.

 

[iwombat]

Re: compatibility 100hp to 115 powerheads

What's wrong with your 100hp, if I may ask.

 

[emdsapmgr]

Re: compatibility 100hp to 115 powerheads

Wombat has the correct info. I'd reuse the intake filler blocks in the 115. It is likely that the 100 carbs have a smaller throat than the 115. Check the flange face on the front of the carbs. If the 115 are larger, overhaul and use them. The intake manifolds are the same. You'll wind up with a solid 115 crank hp instead of the old 115. All the electronics will transfer.

 

[cdoliver]

Re: compatibility 100hp to 115 powerheads

My 100hp aquired a hole in the top right piston, probably due to wrong plugs and a lean condition in the top carb (clogged). The top left has a problem too, though I haven't even took the head off to look at the problem...too scared to. But I found this 115 powerhead ready to go with good compression #s for $250. hope that was a good deal. I don't have the 115 carbs as all I got was the powerhead. So... Now what should I do...???can I still use my old 100hp carbs? or should I look for some 115 carbs too? Gosh, I thought the carbs would be the same, but with different jets... Thanks a bunch

 

[Dhadley]

Re: compatibility 100hp to 115 powerheads

You can use the 100 carbs as they are, no big deal. Do not change jets, they're fine as is. But clean them completely!! You already know they caused or partly caused your current problem.

You can use the 100 intake and reeds too. If you have the intake filler rubbers you can use them too. Or leave them out. At the rpm you're going to turn they won't make any difference.