Neighbors Donzi 4.3...........
 

My neighbor has a '97 Donzi Classic 16 with a Merc 4.3 V6 two barrell. It runs perfectly at all RPM except 1500-2000 it has a distinct miss. RPMs wander distinctly/sharply by 100-200 rpm, like one cylinder cuting in and out. Planes perfectly and smoothly with no miss or power loss under load, no roughness anywhere else, full top end, smooth except 1500-2000. Perfect idle. Any ideas? I thought plugs, cap, rotor, wires, etc. but it planes under load so well with no power loss at all. Good gas. Maybe carb, Carter two barrell. Any ideas appreciated. Thanks.

Re: Neighbors Donzi 4.3...........
 

Carb would be my first guess.

Phil

Re: Neighbors Donzi 4.3...........
 

have to agree with MOP but would check dist cap and plugs before rebuilding carb

Re: Neighbors Donzi 4.3...........
 

Use a timing light and check the timing advance I had one of those last year doing much the same thing it was caused by the timing jumping up and down electronically. Turned out to be a bad ground on the distributor. also remember that if this engine has Thundervolt V ignition it has to be in base timing mode to adjust the idle mixture on the carb..... Ed :cool: