Swapping heads from a 140hp to a 85 hp evinrude

[rolco31]

Hey I have read about people swapping parts from the 140hp evenrude v4 to the 85hp v4 for bolt on extra power. I have a 1969 85 v4 and I was wondering if the 140hp heads would fit on it. I know that many of the parts are the same as the later 70's v4 85 hp's. And I know people with late 70's 85's have done it. If I bolt on some 140 hp heads, will I be safe? have any of you done this?

Sorry, I'm new to all this.Thanks in advance.

Glenn.

 

[emdsapmgr]

Re: Swapping heads from a 140hp to a 85 hp evinrude

Not sure that this will work. The blocks are different bore. The 85/100 hp engines are a 92 cubic inch block with smaller pistons, the 115/125/140 blocks were the 99.6 cubic inch block. The heads are a different size diameter. OMC standardized all blocks at 99.6 cubic inches somewhere around 1979.

 

[kenmyfam]

Re: Swapping heads from a 140hp to a 85 hp evinrude

My guess is that there is a lot more to it than just slapping on the heads. If you want more HP then get a bigger motor. It is a very big can of worms you could be opening up !!!
My 2 cents only though.

 

[Bob_VT]

Re: Swapping heads from a 140hp to a 85 hp evinrude

You will come out ahead if you find the rest of the 140 motor to rebuild and leave the 85 alone.

emdsapmgr nailed it

 

[rolco31]

Re: Swapping heads from a 140hp to a 85 hp evinrude

Thanks guys. Thats what I was wondering.

 

[emdsapmgr]

Re: Swapping heads from a 140hp to a 85 hp evinrude

I had a 72 small bore 100 crossflow. Put a set of 71 125 (1 5/16" throats) carbs on it and some rubber intake stuffers. Picked up about 250 rpm and some solid acceleration. Wound up going up one prop size. I did spend a lot of time rejetting the carbs, however. Took weeks to get it sorted out, but was happy the results.