HP 500 losing RPMS
 

I have a 32 fountain with twin Hp500 carb motors, after i have been running the port motor starts losing about 500 rpms, i changed the plugs,filters wires, does any body have any ideas where i should look next? thanks

compression and cyl leakage

the compresion was good, i should have added it only seems to happen above 3000 rpms.

Did you check the timing?

pick up in tank

i did check the timing when i did the plugs and stuff, i dont think its the pickup because the motor will turn 5200 rms the first couple times i run it up then after that is when it drops off.

outdrive starting to tighten up after it gets warm??

When it warms up check your coil make sure its not shorting to ground will only do this when warm also check sensor inside dist for corrosion.

+1 I had a bad coil wire that would do the same thing.

Mine was simular, check the ground for the ignition pickups. The nut was loose on the port motor and would only turn 4500 wot

Thanks, I'll check it this week. Hope thats all it is

500 hp low rpm
 

Hello, ya better check the valve springs, the inner coils break, triple springs & the crane roller lifter thru pins can come loose and the lifter can get jacked in the block and break and start eating the cam up

Check the little things first, and the coil would be a good place to start they can do funny things when they get warm-hot

Thanks for all the help, it was the coil causing the problem.