15hp johnson age differences.

[BedeMyles]

Hey everyone. Have a quick question. Are the 1986 and 1990 johnson 15hp the same. If not what are the differences. And could I swap one of the blocks over to the other. This is all needed before I buy a 86 to be a parts motor for my 1990.
Cheers, anything is appreciated.

 

[racerone]

Might be a difference in the carburetor.-----Blocks are the same.------Fact.----I believe the crankshaft fits from 1974 to 2007 models.-----In 1993 the 9.9 / 15 went to more displacement.

 

[oldboat1]

get the '86 as a parts motor. Not sure, but an early '86 may have had the t.stat at the bottom, unlike later models. If so, use the head cover from the '90.

 

[flyingscott]

To convert to the top thermostat you need the whole head

 

[racerone]

In some parts of the world a cylinder head might be called a " head cover " I think.----The cylinder head / thermostat change was done late in the 1987 model year.----But there is no telling what has been done to 30 + year old motors.-----Went fishing 15 years ago with a 15 HP 1990 Johnson.----Noticed a water leak at the cylinder head.----Quick inspection told me that head gasket was backwards.-----Owner did not realize this , and told me he bought it that way from local shop.----Fished with the same motor again a few months ago and it runs like new..----Owner wants to buy another rebuilt motor like it from me.------Simply because he wants a spare motor as no shops work or know older OMC products in his remote area.

 

[oldboat1]

To convert to the top thermostat you need the whole head

recalling there is a simple trick to R&R the head/head cover. You might pass that along to the OP.

 

[flyingscott]

recalling there is a simple trick to R&R the head/head cover. You might pass that along to the OP.

Well if you recalled it you could have just typed it?

 

[oldboat1]

BedeMyles -- Do a search here. Has to do with the sequence of bolt removal, as I recall. Watch out for breaking bolts.