porscheguy
Chief Petty Officer
- Joined
- Jan 17, 2013
- Messages
- 441
OK, engine is a 2 barrel 4.3 mercruiser. Serial # 0M322285 which puts its date of manufacture around ‘01/‘02. Bought it as a complete assembly with low hours last year. It’s mated to a gen 1 alpha. Didn’t have to do anything when I installed it. Had fresh oil change and filters. Supposed to have new plugs, cap, rotor, wires, and coil. Ran like a champ all last year. It would have a 21P mirage plus right on the rev limiter. Put it up for the winter and did so properly.
Took it out and it fired right up and settled into a nice idle. I’ve run it several times this season but have not had a chance to run it WOT due to unfavorable water conditions. Had the chance yesterday. First attempt at WOT got me up to 4300. So I backed off. Tried again and it came up to 4400. Then something odd happened. It surged forward and the tach started heading for the redline, but it quickly pulled it back because I was coming up on a wake from another boat. When I attempted to repeat again it came up to maybe 4600 with a lot of trim out. My high RPM for the day was around 4750.
When end I got home I checked a spark plug and it was black and sooty. One thing I will say is when I fogged it last fall, I put about half a can of fogging oil through it before it choked out. I’m wondering if the plugs are just badly fouled? I know when I had my 2 stroke waverunners, if they fouled a set of plugs they wouldn’t burn clean, you had to replace them.
the throttle on the carb opens fully.
My first plan plan is to change the plugs, cap, and rotor. Also I plan to change the fuel filter even though I did it last fall. It won’t hurt to hook up a timing light.
that brief surge really has me stumped. I’m familiar with engines and engine repair, but I’m not sure it this is a fuel issue or ignition.
Took it out and it fired right up and settled into a nice idle. I’ve run it several times this season but have not had a chance to run it WOT due to unfavorable water conditions. Had the chance yesterday. First attempt at WOT got me up to 4300. So I backed off. Tried again and it came up to 4400. Then something odd happened. It surged forward and the tach started heading for the redline, but it quickly pulled it back because I was coming up on a wake from another boat. When I attempted to repeat again it came up to maybe 4600 with a lot of trim out. My high RPM for the day was around 4750.
When end I got home I checked a spark plug and it was black and sooty. One thing I will say is when I fogged it last fall, I put about half a can of fogging oil through it before it choked out. I’m wondering if the plugs are just badly fouled? I know when I had my 2 stroke waverunners, if they fouled a set of plugs they wouldn’t burn clean, you had to replace them.
the throttle on the carb opens fully.
My first plan plan is to change the plugs, cap, and rotor. Also I plan to change the fuel filter even though I did it last fall. It won’t hurt to hook up a timing light.
that brief surge really has me stumped. I’m familiar with engines and engine repair, but I’m not sure it this is a fuel issue or ignition.
