well I have a 1994 150 hp intruder and a 1996 175 hp ocean runner, each of which has one bad cylinder....both motors sport heads with the part # 0338311. the 150 is a GL motor and the 175 is an SL motor,,,,,my 1999 150 hp Johnson has 0337548 heads.......all the parts places say the heads all interchange and fit every 150 and 175 hp motor from 92 to 2006........dying to know whats the difference. I think I have salt build up or some form of blockage in the 1999 150 heads...I just replaced the water pump and its pumping 45 psi at 5000 rpm......but my head temps are still running hot at about 175 degrees...with a infared gun the heads are 155 165 and 175...on each side hitting each cylinder bubble on the heads. going top to bottom..thats at idle....at full rpms, I get the same temps about........ my 1997 175 on my other boat is running less than 120 degrees at 4000 rpms and about 160 at idle for temps and I have 15 psi less water pressure at 4000 rpm.
