Newb Powerhead Swap?

[LARSON69]

I'm new to boating and this site(awesome), and I recently purchased an old boat(one owner 1969 Larson 18' trihull shark) with a 1973 Johnson 115hp outboard. Previous owner said it got hot and has a bad piston. I pulled the plugs and the #1 looked silver and pretty beat up so I pulled the head off. The top of the piston is really chewed up like a piece of aluminum? The cylinder doesn't look that bad so I was wondering if I could just hone the cylinder and replace piston. Also, can I replace a piston without pulling the powerhead off? I also found another power head but I'm unsure if it will fit my unit. The replacement is a 1971 125 hp johnson/evenrude for about
$200. Can anyone give me some good advice. Thanks!

 

[tashasdaddy]

Re: Newb Powerhead Swap?

71 the splines are different, than the 73, 71 is set up for hydro-electric lower unit. 73 is a hydro-mechanical lower unit. you need 73-77.

 

[rndn]

Re: Newb Powerhead Swap?

Welcome to the forum LARSON69!!

 

[ezeke]

Re: Newb Powerhead Swap?

As stated, you can't use the blocks before 1973 and the engines after 1973 are slightly different so you will need the whole powerhead if you use 1974-1977. The 1973 115, 135, or 85HP will work. The 85 has a different bore.

You will have to remove and tear the engine down completely to replace a piston. You will also have to find the cause of the meltdown and correct it.

 

[LARSON69]

Re: Newb Powerhead Swap?

Ok, thanks alot for the good info!