25HP johnson swap powerhead?

[kaferhaus]

I have 2 of these 1990 motors, one is a long shaft one is a short shaft. I need the long shaft in the best condition. Long shaft runs but smokes pretty good and is pull start.

The short shaft runs great and is electric start (which I prefer)

On these motors, the exhaust housings are either short or long shaft, no "spacers" to convert from one to the other.

Would it be easier to swap the exhaust housings/lower units or swap the powerheads? Obviously I'd also have to swap the lower engine housing as the pull start one doesn't have the hole for the electric start button.

 

[david_r]

Re: 25HP johnson swap powerhead?

welcome to iboats!

have you read in the faqs about doing a decarb?

2 strokes will smoke but if its smoking more than the other one -both with the same 50:1 mix- then you probably only need a decarbonization done.

 

[kaferhaus]

Re: 25HP johnson swap powerhead?

welcome to iboats!

have you read in the faqs about doing a decarb?

2 strokes will smoke but if its smoking more than the other one -both with the same 50:1 mix- then you probably only need a decarbonization done.

You could be right and I'll try that, but I really would prefer to run the electric start motor on this boat... I'm not getting any younger.

 

[tashasdaddy]

Re: 25HP johnson swap powerhead?

it would be a heck of a lot easier to drill an hole for a start buttom. rob the starter, solenoid, etc.

Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

 

[kaferhaus]

Re: 25HP johnson swap powerhead?

it would be a heck of a lot easier to drill an hole for a start buttom. rob the starter, solenoid, etc.

That sounds interesting.... so the starter could be mounted under the pull start assembly and then I'd have pull and electric start?

On the pull start motor there are no wires coming from the engine for battery charging... I'm not sure it has a "charging system" how do I determine that? Or would I need to swap all of that too? Actually I'm not sure the electric start motor has a charging system.... as there are only battery cables coming from the soleniod and block back to the battery. And I can't remember whether or not I was hooking the charger up to it when I had the boat with the short transom or not.... Guess I could just start the short motor and put a VM across the battery and check it for charging voltage...

I'm not as stupid as I sound, I promise.... LOL Just haven't worked on boat motors much except for the normal routine maint, water pump repair, carb rebuilding etc.

 

[tashasdaddy]

Re: 25HP johnson swap powerhead?

either way you are going to the service manual for the motor. may as well get one on the way. outboardbooks.com

 

[kaferhaus]

Re: 25HP johnson swap powerhead?

either way you are going to the service manual for the motor. may as well get one on the way. outboardbooks.com

I have one... a Seloc but it's not a very good manual in my opinion... even the pictures are usually so over exposed that you can't make out much and they "skip" a lot of details on disassembly/reassembly.

I'm used to automotive manuals that tend to be much more detailed and have better illustrations.

I also have the parts book for these motors (factory) which is very good. However it only covers the electric start model... so hard to compare everything that needs to be swapped.

Maybe someone has done this manual to electric start conversion before and can chip in....

I know on the earlier motors most of this was much simpler to do as the interchanability of parts was more common.
Especially changing from short to long shaft.... used to be a breeze with the early motors.

 

[tashasdaddy]

Re: 25HP johnson swap powerhead?

here is a good site for part diagrams, etc. http://shop2.evinrude.com/ext/index.aspx?s1=bf6ad09c53cead335fcfd8a6471c0f7f the factory manual is all i use. seloc, is not detailed enough.

 

[kaferhaus]

Re: 25HP johnson swap powerhead?

here is a good site for part diagrams, etc. http://shop2.evinrude.com/ext/index.aspx?s1=bf6ad09c53cead335fcfd8a6471c0f7f the factory manual is all i use. seloc, is not detailed enough.

Thanks, I'd love to find a factory manual for this motor but I've had no luck... the ones I've found on ebay usually don't tell you what year model is covered.... I've even emailed the sellers and usually they never respond.

 

[Harker]

Re: 25HP johnson swap powerhead?

For an electric start conversion/swap you probably would have to swap flywheels too so it had the teeth for the starter...then the pull start probably wouldn't work. I'm contemplating doing this with an 88 20hp electric/remote start into my 90's 30hp tiller motor pull start. I will just swap the power heads but I have to put a new gasket between the mid section and lower pan since it leaks. That is harder than just swapping powerheads. Drill a hole for your start button and cables on the longshaft. Ken Cook should have a factory manual for you, I have picked up a couple off ebay but you have to make sure that it is for your model and year specific.

 

[samo_ott]

Re: 25HP johnson swap powerhead?

Guess I could just start the short motor and put a VM across the battery and check it for charging voltage...

That's the easiest way but it does not sound like you have charging. You'd see more wires, a terminal strip, rectifier... etc...