How do I make my evinrude 90hp a 140hp???

[tico frank]

I have a 1985 evinrude 90hp model and it runs like a top. It's too small for my 20ft hydrostream voyager. I can't afford a new engine right now but I was wondering what can I do to bump it up to a 140 model. Is it just the heads or the heads and the carbs??? Please help.

[chynewalkr]

use the search function. try searching v4, bubble back, crossflow. this topic has been covered many times and youll likely find more info than youll ever need.
btw its more than heads and carbs, its also an exhaust tuner (the bubble back) and other related parts, like exhaust stuffers and intake filler blocks, but like i said do a search.

[SportJ-US-1]

To properly upgrade it you will be spending some bucks as you need heads, carbs rejet or maybe different carbs (probably), reed stuffers and exhaust changes. Oh yeah and a bunch of machine work for the port changes, intake and exhaust.

[tico frank]

Well i'm no evinrude mechanic so am I getting myself into some I should not because I don't mind buying a few parts like carb, reed/intake, and other parts but when you talk about port changes/ machine work that just sounds like i'm starting to get over my head? Ithought the only difference is the heads, carb and intake?

[chynewalkr]

"I thought the only difference is the heads, carb and intake?"

Nope, you need an exhaust bubble, exhaust stuffers (requires some machining), youll need to open up an area in the exhaust cavity. different porting. rubber stuffers in the intake manifold behind the reed cages. in addition to the heads carbs and intake

you're better off saving for a v6, converting it to the 140 will probably kill some of the bottom end that you need to get that boat up on plane, and your top end probably would only increase a few mph.

[hsbob]

the bubble tuned exhaust is a bolt on system. you do need the filler blocks. do a search and there is now a source for them. if you 90 is prop hp then its a 115. if not you may not gain much due to proting. i gained about 5-6 mph by adding just the tuning pack. this was $300 in 1979.


you also need the 140 carbs, but that too expence for the real benfit.

save you money for a 200hp.

[Stretch]

Sell the 90
omc v6's are pretty cheap here