OMC XP, GT outboards

[SML Boomer]

How do these motors differ from other models? I read on a search that the ports were larger and easier breathing. Is there anything else? Also, does an engine rebuild undo the XP/GT package? The mechanic said he used thicker head gaskets to lower the compression for poorer quality gas.

 

[Benny1963]

Re: OMC XP, GT outboards

i believe they had a little better heads and maybe some jetting
but not really shure you can do a search on the xp and gt
and look at some old threads i have a 175 crossflow and it is my understandingthat the xp and gts are the performers of the crossflows
someone will come along this will keep your post alive

 

[emdsapmgr]

Re: OMC XP, GT outboards

These 150 engines used the same blocks, but had added performance items. The XP/GT used different heads, 175 (1 5/16") carbs. They had stiff lower engine mounts, special decals and vented hoods. Most had the special 35 amp alternator. They put out 10% more hp than the cowling said. (around 165). The 2.6GT/XP had other special items in addition to the above. Any rebuilder should reuse all your same parts. Some of these GT/XP's ran up to 30 degrees timing from the factory. I'd probably run standard head gaskets on premium gas and reduce the timing somewhat.

 

[SML Boomer]

Re: OMC XP, GT outboards

Thanks much. Is it likely that the thicker head gaskets is responsible for a 200-300 rpm loss that I am experiencing? Motor sounds smooth but does not seem to have the zip it has before replacing the gaskets and the voltage regulator.