hp 500efi rev limiters
 

what is the rev limiter on a hp 500efi 5250 or 5400 turning props at 5150 want to know how much more I have to go

I believe:

4800-5250 is normal op

5400 is rev limit

Rev limit is supposed be at 5350rpms. Keep in mind this can vary 50-100rpms and tachs can be off as well.

griff I have a 32 AT 2002 , I pulled the motors and did the top end I beleive after doing everything that I am now down approx 150 rpm and 1-2 mph. Top ends have inconnell severe duty and manley valves, hi comp springs. Drives and props all the same, all the alignment is the same. We also put in new mounts to realign the motors the drives would not go back on also replaced one coupler. I thought it should run better, at a loss

Sounds strange for sure. Is the speed off 2mph as well???? If you're down 150 rpms, and everything else is the same, it should be.
Did you change cams???? or just basically a stock refresh with better parts??? What valve springs did you use???

It could be as simple as a valve or 2 being just adjusted a little too tight or not tight enough.

hi comp springs, Your thoughts are the same on the valve adjustment, was going to look at all that this weekend and just go through everything again. what are you running in your boat and did you ever run hp500efi.

I have 502mpi's with CMI's and Stelling boxes. It runs 72-74mph. I've had the boat 2 years and bought it from the second owner who had the engines installed. It was originally built with 700+ HP SC'd engines and ran over 100mph.

what affect do the boxes have for you , I also have a pair of nose cones but not shure if Im going to use them. I have stock bravo's and have heard mixed emotion on the performance of them.

I don't know for sure. It was built with them originally. It seems my prop slip numbers are maybe a little lower than most other 32's. I do not have a notched transom, like the newer 32's though. It still has the original 1.36 drives with nose cones as well. My engines are also moved forward a foot with driveshafts to help give the boat better balance.

Rev limit is 5400, peak power is 5600rpm if you raise rpm limit, motor has 28deg timing from 3600-5200 and 34 at 5400.

Dustin couldnt the motor take more timming? or have to run 92 etc?

Rob

I was told about the time advance between 5250 and 5400, I beleive my motors ran about 5300-5350 before redoing the top end. When I spoke to one of the guys helping me about the time advance said no. I have a rinda scan tool , looks like Ill be running the boat this week and I will find out exaclty were everything is. I f you have any other info let me know. What affects may there be from bumping up the rev limiter and I also was told a liitle time advance might not hurt, give your thoughts.

griff was the boat built that way or did you change it.

It was built that way at the factory. It was built for OSO member Drag n Ass in 1997.

Don't know if you already solved the problem, but have you checked the timing? I once had the same prob with 502EFI years ago in a 38 scarab, after rebuild the base timing was set to low, they should time at 4000 rpm

That's not true. They need to be put in base timing mode and set at 8 deg. By putting them in base timing mode, you take the ecm out of the equation as far as timing is concerned. You can put it in base timing mode with a scan tool or by jumping out the A and B terminals of the data plug. You can use the jumper plug or do it with a piece of wire or a paperclip.
Eddie

yeap:drink:

that's not thrue, you put them in timing mode (we use the dtt or newer laptop) and you time them on 4000, like a carb engine, that way you are 100% you have the complete timing degrees available, had the exact problem before, was a mercruiser factory tech who told me and turned out just fine

to get this correct put the motor in base timing mode, run it to 4000 rpm and set the timing on 4000rpm. I watched them set the timing on the motor and it was not done that way. If you have a set procedure please explain, also I have a rinda scan tool available to me what can I check for to make sure it is done properly.

so what was your total timming at 4000?

You put the motor in base timing mode and you only need to rev it to 1250-1500 and set it at 8 degrees. Some cals call for 10 degrees. Also some engines do not like the 34 degrees total the spark retard kicks in and it loses power.

After the timing is checked maybe do a leak down. I did have a bad valve job from a machine shop on a new motor. Ran it on the dyno and didn't do to well. The leakage on one cylinder turned out to be 40%. I ran it again on the dyno in the exact same config and picked up 25 hp. Just a thought.

Have not had a chance to check timing will try this weekend, I did run it a few weeks back with the rinda tool on it to see if it would advance at 5250 and it did but the motors were off like 2 degrees from each other. I was by myself and did not have alot of time so I will try it again with some in the boat with me. trying to go wide open and look back at that monitor on the back seat is not easy. Thanks for the input.

Please enlighten me. What was the timing at 4000 rpm? I can't believe me and every other engine builder have been doing this wrong for the last 20 years.:rolleyes: You can not check total timing with it in base timing mode. The ecm will add 10 deg. past 1800 rpm when in base timing mode. Total timing is determined by the calibration. It is based on the initial timing, which is usually 8 deg on Mefi 1,2,and 3. Usually the Mefi 4's use 10 deg. If the initial timing is set correctly, then the timing will be whatever is programmed in the cal. If initial is set at 12 deg., then there will be 4 more deg. of timing throughout the entire cal.
Eddie