johnson/evinrude 20-30hp conversions

[Triangleboater]

Can anyone point me to a list/thread/site that has what years the 20/25hp johnnyrudes can be converted up to the 30/35hp? Also what goes along with doing the conversion. I have searched the forum and can only find contradicting info.

Story is right now I have a 69' 25hp. I know it's really only pushing out 20ish hp at the prop and will only barely get on plane with the wife and I. Add a cooler of beer and we are a barge. I have shifted all the weight around I can. Simply just need a little more umph. I know after 86' they rated them at the prop so I figure I am already ahead if I go with a 86' or newer 25hp, but I figured if I could increase that to 30 with just a little work I would be in business for not too many $ bills.

Thanks!

 

[BigB9000]

Re: johnson/evinrude 20-30hp conversions

Parts are cheap.
Just look for a 35hp?

 

[Willyclay]

Re: johnson/evinrude 20-30hp conversions

Lots of good info in this thread: http://forums.iboats.com/johnson-evinrude-outboards/converting-20-hp-johnson-35-hp-274566.html

 

[F_R]

Re: johnson/evinrude 20-30hp conversions

Can anyone point me to a list/thread/site that has what years the 20/25hp johnnyrudes can be converted up to the 30/35hp? Also what goes along with doing the conversion. I have searched the forum and can only find contradicting info.

Story is right now I have a 69' 25hp. I know it's really only pushing out 20ish hp at the prop and will only barely get on plane with the wife and I. Add a cooler of beer and we are a barge. I have shifted all the weight around I can. Simply just need a little more umph. I know after 86' they rated them at the prop so I figure I am already ahead if I go with a 86' or newer 25hp, but I figured if I could increase that to 30 with just a little work I would be in business for not too many $ bills.

Thanks!

The 1969 25hp is the 22 cubic inch motor, and is already tweaked for the maximum horsepower they could get out of it. After all, the design started life as an 18hp, back in 1957. No way in heck are you going to make a 35 out of it. The 35 is a totally different motor, top to bottom.

 

[Triangleboater]

Thank you, but i guess I forgot to mention i was looking to repower all together. As in get a newer 20-25hp and upgrade to the 30/35. I know that my engine now is already the tweaked small CI engine.

Does anyone know what year the 20/25's can do the upgrade and what is involved? I know that there have been threads about this before, but i was looking for a consolidated list. If not, I will begin the dig through.

 

[Chinewalker]

Any of the 31.8 cui 20/25 hp models with through hub exhaust can be converted to 30/35 spec, as outlined in various threads here on iboats. Keep in mind that the pre-1986 35 is essentially the same as the post 1986 30...

 

[F_R]

A large part of the increased performance from a 35 comes from the thru-hub exhaust gearcase. But a word on that...my advice is steer clear of the pre-1980 ones. They had serious overheating problems. 1980-up have the side water intake on the gearcase. That's the one you want.

 

[Triangleboater]

perfect! just what I was looking for, so any 1980's model, 20 or 25hp. The 28 had non-thru hub right? so no go on that.