rev limter

stevesxm · 12-14-2005, 10:49 AM

have 96 , 38' cig top gun. two , 100 hour 502, mag mpi box stock. bravo 1's with 24 props. am new to the boat and have just gotten it together and doing sea trials. everything works like its supposed to. however 54 mph ( gps true) is as fast as it goes trimmed out in perfect conditions.... the motors get to 4500 and just stop there. are these things rev limited ? the reason i ask is that even in less then perfect conditions it does the same thing.... doesn't seem drag limited.... seems to repeatable for that....

Pat McPherson · 12-14-2005, 11:09 AM

Rev limiter are at more like 5200rpm.
Those engines make max power at 4800-5000rpm.
Does seem a bit slow, ask over on Cig. forum if you've got the right props.

stevesxm · 12-14-2005, 12:06 PM

thx...will do

sleeper_dave · 12-14-2005, 12:19 PM

check ignition timing

i had my motor rebuilt last year (single 502) and was still only getting 59 mph out of my 27 fever. i bumped the timing up 2-3 degrees from stock and picked up 2 mph. I think i need to play with the carb now, the plugs looked pretty rich when i winterized it.

stevesxm · 12-14-2005, 12:30 PM

these motors are efi... but for the record, running your motor rich is the single worst thing you can do to it. the extra fuel ends up in the oil and dilutes it, washes the oil off the cyl walls so they don't seal and won't make power any way... bumping the timing picked up the combustion chamber temps a bit and got rid of some of the extra fuel so that " increase " you saw wasn't real.... it is just masking the symptom that will ultimately junk your motor.

800XCR · 12-14-2005, 12:49 PM

Something doesn't add up. If it were the wrong ecm, it could limit it to 4600, however, it would have most likely burnt it up as well. Tachs could be wrong, or someone could have altered the ecms. See if you can get a checksum number off of the ecm or have someone get the checksum number out of the ecm.

stevesxm · 12-14-2005, 02:18 PM

Quote:

Originally Posted by 800XCR

Something doesn't add up. If it were the wrong ecm, it could limit it to 4600, however, it would have most likely burnt it up as well. Tachs could be wrong, or someone could have altered the ecms. See if you can get a checksum number off of the ecm or have someone get the checksum number out of the ecm.

maybe can do... THINK local dealer has the computer interfaces to read the boxs however... these motors were takeouts and where absolutely complete and factory when i got them. every single nut bolt washer screw and tie wrap is factory so i am convinced the boxes are correct. also... they run great. start instantly make real power , accelerate f;lawlessly... checked the plugs before i reinstalled the motors and they were perfect....

just gets to 54 mph 4500 on both tachs EXACTLY and stops right there... like it had a soft limiter that i couldn't feel... and i don't mean 4435 or 4511 revs... i mean the needle SPLITS the 4500 line on both tachs... and stops rite there....

i want my other 600 revs.

800XCR · 12-14-2005, 02:59 PM

Maybe you have taller ratio drives and 4500 is all it can spin them. You asked for help, I gave you some advise to clarify ecm info which is the only thing that controls the rev limiter on a stock 502 efi/mpi and the title of this post is rev limiter.

Pat McPherson · 12-14-2005, 03:44 PM

Quote:

Originally Posted by 800XCR

I wonder why real useable advice gets harder and harder to come by?

I'm sure that your advise is appreciated...

Try smaller props.
If they still don't spin past 4500 then there is another problem besides not enough power...

The Menace · 12-14-2005, 06:41 PM

Smaller props. You may be lucky to see 58-62 mph. Takes a lot to move a TG.