15 / 18 Evinrude powerhead swap?

[twocyclemania]

I have a 59 Evinrude 18 with a bad powerhead. I also have a decent 15 Evinrude powerhead (and carb) of 55-56 vintage. Anybody know of any problems in switching the two. I plan to use the 18 mag plate and flywheel. thanks

 

[samo_ott]

Re: 15 / 18 Evinrude powerhead swap?

I've never tried. They are different blocks though. The 15 is a 19.94 cu in and all the 18's are the tough-as-nails 22 cubic inch. It's not hard to try. Or, what I would do is compare the base plate gasket # and see if they're the same. If yes, then it should bolt up.

You might have to switch the carbs though for the needles to line up.

 

[1946Zephyr]

Re: 15 / 18 Evinrude powerhead swap?

The '59 and newer 18's were built with a thermostat type cooling system, so the older powerhead will not work. If the 18 was '58 or older, it would have. What is wrong with the older 15? If the lower unit is bad, you can take the lower unit off of the 18 and use it on the 15.

 

[twocyclemania]

Re: 15 / 18 Evinrude powerhead swap?

Thanks for the replies (samo_ott and 1946 Zephyr): I'm not sure I understand why the 15 won't work because of the thermostat. Does it have to do with the mounting? (or) How does having a thermostat on the powerhead I'm removing rule out the older 15 powerhead? I would think that if things line up it would work. Please elaborate. thanks!

As for the 15 - it was a powerhead I picked up years ago. Unfortunately I don't have the rest (lower unit) of it.

 

[1946Zephyr]

Re: 15 / 18 Evinrude powerhead swap?

As I recall, since the later motor has a thermostat set up, things are different as to the water circulation, so there may be differences in how they mount up and the design of the gasket and such. You can look at it real close and see if they look the same where they mount. If they do, then give it a try. 1955-56 does have a mid section that is very close to what the 59 has, but the shrouding is just differenent. Someone else here might chime in, who knows for sure.

 

[twocyclemania]

Re: 15 / 18 Evinrude powerhead swap?

I recently had a newer 18 (62 - 63) apart and if I'm not mistaken there is one hole in the block at the mounting (and matching in the lower unit) where the water is pumped into the head. The 15 has two holes so I'm sure the 15 powerhead cannot be used on the 18. Does anybody know why there are two holes (intake / discharge?)? How is the circulation on the two different. You would think they would be the same since the 15 is a close cousin of the 18. I'm curious! thanks

 

[Shane7]

Re: 15 / 18 Evinrude powerhead swap?

I used two 1960 powerheads on a 1956 15 Johnson and a 1957 evenrude the way the water circulates you have to use 1958 and newer heads

 

[HighTrim]

Re: 15 / 18 Evinrude powerhead swap?

As Zeph stated, due to the t stat of the '59, the powerheads are not interchangeable. Base gaskets are not the same either.