Here's the deal..... Since I've put my motor back together with heads, cam, exhaust, carb, new case gasket, new lower seal, I've notice that the motor is missing when it is in it's normal trim position. If I trim it down to the point the entire prop is under water, it goes away. Trim it back up and it starts missing again. This happens in the water only. I'm running a near new stock prop and have never had this problem before. Any suggestions?

Do you have a rev limiter? If so, sounds like you could be bumping it. With a stock wheel, with my motor trimed out it bumps it. Had to get a prop with more pitch or lower the trim with a stock wheel deeper into the water to get it off the rev limiter.

Yes, it has the rev limiter. I suppose it's possible, but my tach does not suggest that I'm bumping it. With the prop all the way in the water, it's around 4100-4200 rpms. When I bump the trim up just a touch, it starts missing.

With a light load, (me and 2 boys and fishing gear) I could get 31.4 in deep water. Just me, only 28 mph????

Would it be stupid to unhook the rev limiter for a just a bit just to see if this is the problem, so long as I don't run it WOT?

Just cut the wires and see what happens. You should be able to run that motor at atleast 4600 rpms in the water if the motor will turn up that high. What chip are you running in the limiter?

If the rev limiter is working, don't cut the wires...just pull the chip out of it. Then it will default to 5600 rpms.

the chip says 13.8

I thought it was a 4800 chip but am not sure. Anyone know?

So is my only option to switch to a bigger prop? Or do they make a 5000 rpm chip?

I tested mine out of water and it seems to kick in around 4600 rpms too.

Third one down Myboy.

http://www.allmudmotors.com/products/b-p-s-rev-limiter

Not sure you want a rev limiter chip that high, I was told the stock connecting rods are the next point of failure after the valves are shimmed and ~4600 is where you want to max out. Its a protection device for over revving if the motor pops out of the water.

Go run it without the chip (defaulted to 5600) and see where your motor wants to run, just be careful. If you are hitting where the rev limiter kicks in at the optimum trim, then you can add a more agressive prop to add more engine load and adjust your RPM down (but may increase performance).

I can testify to the fact that the push rods are the weak link and they will fail above 4600 rpms...bent both push rods on one cylinder on mine a few weeks ago letting another guy drive it in shallow water trimmed up too high. He was bumping the rev limiter (4800 chip). We were on the very opposite end of the lake from the boat ramp when that cylinder dropped. Managed to get back to the ramp on the other cylinder, and luckily the only damage was 2 bent push rods and a blown head gasket (that was from running back on the 1 cylinder only). Moral of the story...I wouldn't run it above 45-4600 without adding the beefier push rods. I ordered a 4600 rpm chip to make sure it doesn't happen again.

Update: Took the boat out fishin yesterday. It definately is the rev limiter kicking in. New2duckin had a 12x14 hopkins cleaver for sale in the classifieds, so I picked it up from him. From what I've read, with a stage 1 and a cam, it ought to be about perfect. Thanks for all the help.

I look forward to hearing how it runs with the hopkins...I've though about adding a little more to mine when I do the gasket. Post back up after you get the prop with the new results, please.

where is hopkins propeler located?

I think the chip for 4800 rpm is a 17.8 k resistor you can go up a little to a 20 k and it will give about 100 rpms from what I calculated. You can usually find resistor at radio shack for about $1 but you have to carefully cut open the little yellow box and soldered it to the pins, you may also solder a potentohmeter say a 30 k and dial in what you want for rpm , but it is not very water proof.

I got to agree with River. If you are going to drop the pot on them at least spell it right so they can google that mofo.

potentiometer

Sorry bout the spelling had three coffee's and running wide open!