1995 Johnson J6REOD WOT issue

W

WestPoint

Seaman
Joined
Apr 3, 2009
Messages
58
Ran this 2-stroke for 27 seasons on a 14 ft Alumacraft Model A. Having issue this summer where at WOT it doesn't reach its normal range of 4500 to 5500 RPM, whereas it had no issues before. With my 8.5x9 prop only hits 4280 RPM, and with my 8x7 prop only 4700 RPM. (with just me and normal gear in boat). I didn't have a tach in prior years, but it was absolutely much faster. So this is where I'm at:

1) Did sync and link, and noticed that it ran best with idle screw 6 turns out, in forward at 700 RPM. This seems way too rich, but starting place was 3 turns out per manual and it would not stay running. It wasn't happy until 6 turns out to run a consistent 700 RPM.
2) Temp and water pressure tested fine (new thermo and water pump rebuild in spring).
3) Did a propane gas test around intake while at idle and found no air leaks.
4) Compression identical on both cylinders at 95 PSI warm.
5) Spark jumps 1/2 inch on both, and I can actually start the motor on two pulls with only one spark plug wire attached (tested both cylinders this way).

I'm thinking this is fuel related and ordered the carb and fuel pump rebuild kits. I decarb every couple of years, and last rebuilt the carb and fuel pump in 2020. Do you think I'm on the right track? Any thoughts? Thanks, Jim
 
C

Crosbyman

Vice Admiral
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Nov 5, 2006
Messages
5,027
maybe it is aging nicely after 27 years ... is it a 1500 hrs plus engine or a weekender engine with 600hrs ??

95psi may or may not be low....experts will tell.
 
T

tphoyt

Ensign
Joined
Jun 10, 2010
Messages
930
I would confirm those number with another garage. Borrow a gauge from a friend or auto parts store. Lower compression will effect your top end power. If they are that low you could toss a wrench on the head bolts and resurface the head and replace the gasket and see where that gets you. Being you already have have pump and carb kit on the way may as well do it.
It could just be getting tired after all these years.
Best
 
W

WestPoint

Seaman
Joined
Apr 3, 2009
Messages
58
Crosbyman said:
maybe it is aging nicely after 27 years ... is it a 1500 hrs plus engine or a weekender engine with 600hrs ??

95psi may or may not be low....experts will tell.
Click to expand...
I wish that I recorded PSI when I first got the motor to use as a future reference. I did record both cylinders being at 100 PSI four years ago. (I keep a log) I would say hours are on the low side, but with regular use. I have 4 boats with 2-strokes. One, a 1986 Evinrude 90 that I owned since new, had 126 to 130 PSI nine years ago. I think I read somewhere that the smaller HP's normally had less comp. None of the OEM shop manuals I have mention a good range, they only say that variation between cylinders should not exceed 15 PSI on the 6 and 8 HPs .
 
R

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,315
Checked reed valves ?----Any pieces broken on the throttle cam?----Throttle plate going full open ?
 
Last edited:
W

WestPoint

Seaman
Joined
Apr 3, 2009
Messages
58
WestPoint said:
Yes plate goes to full open.
Click to expand...
Good point about checking the reeds, which I'll inspect when rebuilding the carb. The leaf plate, part 393959, I believe was used on 6/8hp from 1984 and later. In case mine are bad, I emailed CCMS to see what years their composite reeds cover (their part 133S/4/6/8).
CCMS # 133S/4/6/8
 
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