powerhead swap

[hawkman222]

I have a 1985 90HP Evinrude with a blown powerhead. The model# is E90TLCOS. I've located a used 1979 85HP Johnson powerhead model# 85TL79R and would like to put it on my Evinrude. I plan on using the electrical off the blown 90HP and putting it on the 85HP. They both use the same powerhead to exhaust adapter gasket. It looks to me like it should work. Does anyone know of any reason it won't work? Is there anything you guys see as a potential problem with this swap?

 

[Chinewalker]

Re: powerhead swap

Should be an easy swap. I think I would keep the 1985 fuel system, too, as I believe (and I'm sure they'll correct me if I'm wrong) the later carbs have a better idle circuit system. They also have the primer system, as opposed to the choke system. Not sure which is better on that front, but if you use the later carbs you'll have to use the primer system, too...<br /><br />- Scott

 

[hawkman222]

Re: powerhead swap

Thanks Chinewalker! I think I will use the later fuel sysytem. It's VRO and the other isn't, but I don't think that matters. I hope I'm not getting too far off subject here, but if these two blocks are interchangable, and have the same bore (3.500), why is one an 85HP and the other 90HP?

 

[emdsapmgr]

Re: powerhead swap

THE 1979 WAS CRANKSHAFT RATED, THE 1985 IS PROPSHAFT RATED. ALL THINGS BEING EQUAL, THE 1985 MAKES SIGNIFICANTLY MORE H.P.--EVEN THOUGH THE BLOCKS ARE BASICALLY THE SAME. POSSIBLE THAT THE 90 CARBS HAVE A LARGER THROAT AND IF USED ON THE 79, YOU MAY NOT SEE MUCH A DIFFERENCE IN PERFORMANCE.