2.5 200 EFI bump compression

[bep078]

Hi,

What can be done to a stock Merc 2.5 200hp EFI (non promax) to add some more power without decreasing longevity too much? I read that the reed cages are ported and heads are skimmed to bump up compression. Can these be done as it is an EFI engine?

[HStream1]

Milling heads is the best bang for the buck. A quality reed change never hurts either. But before you do anything make sure the condition of the engine is up to par. A compression and leakdown will tell you alot. Bumping compression on a already worn out motor will definately shorten it's life span. And yes it can be done on a EFI.

[bep078]

Thanks.

Motor has been re built and has approximately 10 hours. When milling the heads, does the ecu need to be adjusted to add more fuel?

[HStream1]

Should be ok. You're still going to be running pump gas. Just keep in mind the additional cost of 87 oct vs 93 oct. What year motor?

[bep078]

1998 motor. Started life as a carb motor but then the EFI system was installed instead of carb. How far can compression go up to 'safely'? And what cc will that roughly equate to?

Thanks.

[HStream1]

140/145 psi and that usually works out to be 34/35 cc's on a fresh motor.