300 X / 300 Promax comparison

[mercracer2.5]

What is the main difference between the 300X and the 300 Promax? Are the electronics and fuel system the same? Is just the block different?Which one can you modify more and easier?

Thanks,
John

[PropWash]

There are quite a lot of differences.

300x has optimax style intake plenum with large butterfly at top, 300 Promax has normal EFI 3 litre style intake
300x has electronic oil injection (good reliability), 300 Promax has older style gear driven oil injection
300x has different engine electronics
300x has higher rev limit and makes its power at higher RPM, so is much easier to prop on a light boat

I expect the porting etc is different too, although I don't know about that. 300x is definitely more of a race oriented engine than Promax 300. I ran a 300x for ski racing for a number of years and it was great. Now I have a 300XS, which is also nice but not quite as angry as the 300x.

There seem to be plenty of 300 Promax engines still running with big hours, so they are a decent engine. However, 300x is an awesome engine in every respect (some would argue not good for fuel consumption - which is high).

[crissylou]

exellant reply propwash

[MaDneSS]

anyone know if its possible to transfer all electronics and intake off a blown simon 335 (300 promax) onto an 300x long block

[shooter1]

I'd call Eric Simon. If you can't he might cut you a deal on something that would work for you. Great guy to talk to and he knows his stuff.