JOHNSON 2 STROKES

[KIMO]

Hi Im in South Australia so Im not sure if there will be any interest shown in this post but I am more looking for coment and if any one has experienced similla problems.
I had a Johnson 115hp 2 stroke motor on thew back of my boat a 1995 model purchased in 1996 new. I had given it reasonable recreational work over the past 9 years, probably on average about 4 hours running a month, don`t do a lot of trolling over here.
About 18 months ago 2 cilenders had chucked it in , the motor was pulled down and 2 oversized pistons were fitted,other 2 cilenders honed and new rings fitted. Last weekend on the way in I lost power in the motor. Back on shore an inspection revealed one of the honed out pistons had badly scored and one of the oversized pistons was very slopy, this motor had done minimum work since its rebiuld and i would normaly put it down to a bad rebiuld or just a very tide worn out motor. However 2 other johnson motors on boats in holliday shacks close to mine have experienced the same fate over the last 3 months, the other motors were 90 hp of the same year as mine.
My question is, is this normal life expectancy of these motors , or is it the oil injection breaks down or fails to deiver oil to some of the pistons, or concern is it fule adatives being used that may not be compatible with 2 stroke motors, perhaps acceptable in cars but unagreeable to long term outboards. or is it just me being dramatic .
Your opinions please ,Cheers KIMO

[Spaniard_King]

Kimo,

your engine had a bad adpter plate (between the powerhead and trunk) this was replaced with a modified version. Have you had this done?? This should have been done early on in its life under warranty. this adapter used to let water into the bottom cylinders

Garry

[Noelm]

There are a lot of things that can affect the life of a 2 stroke, first if you cannot get to full RPM about 5,500 to 6,000 you have the wrong prop and the motor is "labouring" and will cause serious piston/bore problems (detonation) next the oil system must be in good shape and working correctly, also the carbies must be clean to prevent a "lean" condition which will fry a piston in a jiffy, as I am sort of thinking that whatever caused the first failure was never rectified and caused the next early death, best find out the cause before you rebuild again, a modern 2 stroke with regular care and water pump replacements etc will last for thousands of hours, they usually die from a preventable failure long before they wear out.

[osmosis]

I heard a similar story to what spaniard_king said. Apparently there is a gasket under the powerhead which becomes brittle and lets water in. Bloke I work with owned a mid 90s model 90hp, he upgraded to a new evinrude but wouldnt sell me the johnson as the outboard mechanic informed him of this inherent problem.

[KIMO]

Thanks for the input guys.
Spaniard King & Osmosis
Never had any call backs on the motor so Im cirtain there was no adaptor plate replacement, but would have thought the machanics rebiulding the motor should have picked that up when rebiulding it if it was nessesary,but i definatly don`t know,and it may have been the cause .
Noelm.
Very interesting coments , the motor would peak rev at 5500rpm ,not that I run it at that speed a lot mostly around 3500/ 4500 rpms.
Had 2 fule filters on it 1 standard in motor filter and an aditional larger in line filter mounted between the tank and the motor, this one has a drain bowl under the filter can be drained at regular intervals, which it was .
The oil I am uncirtain of as it was oil injected, however i would often mark the oil leval on the resevior and check it at the end of the day to see if it had lowered ,which it would .
LEAN FULE: had a friend in the garage one day claimed he knew a lot about these motors !and pointed out a small red valve cap like object on the top of the carburetor he turned this a bit one way with his fingers telling me it would lean the fule down and improve the fule consumption.
From your explamation here with in may be the cause , will make a few more enquries along this line.
Once again Thanks guys I wont have the motor rebuilt at this stage I am having a new Yammaha 4 stroke fitted tomorrow but would sill like to know what caused the burn out .
Cheers Kimo

[mangrove_nick]

gday
i brought a new 15hp johnson it broke down after 15 minutes. i had to get a toe back in. the dealer had a look at it and it had a small scratch on the bore. after that it hasnt missed a beat.

cheers nick