Donzi38ZXXX

Just curious - When rebuilding a 500EFI - How much horsepower can you get out of a 500EFI and still use 87 octane fuel.

mcollinstn

okay, not trying to be smart here, but a rebuilt 500EFI will have about the same horsepower as a new 500EFI.

I'm guessing that you are asking what you can DO to a 500EFI to get more hp and still run 87 gas. Now we need you to be more specific.

When you say REBUILD, I would normally assume you have a tired motor that needs freshening up. If that's the case, then you are probably asking what parts to substitute internally in addition to external parts that will maximize your hp bang for the buck. If your motor is not TIRED, but is still fairly fresh, then you may be asking what BOLT ON or external parts will help you make a monster out of it. This would include intake and exhaust mods yet would not include internal parts.

So there is a whole world of answers to this question.

In order to give you the best ones, you'll need to finish this "checklist"

1) Is your motor tired, or is it still pretty fresh?
2) Do you want to include parts INSIDE the motor for your buildup or just stuff you can bolt on with the motor still in the boat?
3) Do you want to retain the stock EFI setup?

If we are going inside the motor, do you want to keep stock bore/stroke?

hate to answer a single question with twenty new ones, but......

mc

Donzi38ZXXX

I meant when ready for a complete rebuild (meaning tired engines - 500 hours+/-) of an existing 500EFI - how much could the horespower be increased (not rebuild stock) and still use 87 octane fuel.

At this time my EFI's are not tired with only 192 hours and run hard maybe 5% of the time plus well maintained by me.

I was just curious when I reach the "need to rebuild" time how far can you go up on horsepower and still run 87 octane.

Sorry for the confusion.

Joe

bored my old one to 540 and sent off the computer. needed 93 afterwards, and if caught in a pinch, I was safe to run 4k max RPM's -- said both the computer guys and my engine builder --- but not optimal and still an issue of detination etc....

the guy that bought the boat from me ran it in excess of 1 yr. and called letting me know how pleased he was with the engine pkg. (nice call to get).

Joe

Pismo10

As long as you keep the compression reasonable you can make lots of hp with 87 pump gas. Use aluminum heads and you can buy yourself some more compression as well. Add cubes, great heads, great exhaust, a cam, remap and you probably could go to 600ish hp on 87 gas.

Dock Holiday

I really did not like using 87 in the stock 500's. We rebuilt mine at 300 hours, changed heads, cam and reprogramed the ECM and they dynoed at 598 HP at 5300 RPM. We did also bump the compression up to 9.25:1.

All three people involved in the rebuild told me to always run 93 Octane.

I have done some coastal trips where 93 culd not be found and simply ran the boat easy and had no problems.