Down RPM's 1985 175 Johnson

[yrag]

I had a bad reg/rect.for awhile and finally fixed.I took the boat out and wot rpm was 4700 trimed out for max rpm.I do have the low compression head gasket and set the timing at 28 deg.(stock 34 deg.)The compression is 90-94 all cylinders,and good spark(at idle)The rpm used to be about 5300-5400.The engine runs great just with lower rpms. Boat is a 20ft.c.c. 20deg.v and has a sst 15x17 prop.Do you think this is do to the timing and lower compression? Any ideas or sugestions greatly appreciated.

 

[clanton]

Re: Down RPM's 1985 175 Johnson

The service bulletin I have says that if you install the low compression head gasket the engine timing remains the same, no change, sb2155 dated 1986 for 86 grade fuel. Then service bulletin 2159R1 dated Oct 1988 says that if you use 88 grade fuel, retard timing 4 degrees, no change in head gasket. If you use 91 grade fuel no modifications neccessary, use standard timing and gasket.