496 Stroker...irratic rpm..stalling
 

Hello everyone. I am stumped on the issue that I am having. I recently had a 496 stroker built. We installed it and it ran great for about 200 miles. Like an idiot, it ran out of gas on the gulf and we had sea-town bring us 6 gallons to get home (we took a few heavy waves in the engine bay while the hatch was open (Baja 232).

Sea tow brought us the gas and it started right up. We drove about 4 miles home, flushed the engine and the boat sat for a while. Next time out, the boat won't go over 3k rpms after the 1st minute out. It jumps between 2500-3000 rpm..almost in rhythm when I try to give it throttle. At first I thought I noticed it shutting down even more when the boat rocked or I hit a wave..however, It wouldn't go above 3k.

I noticed the volt meter was reading low and the tach going to 0 while underway when I press a button or move the trim.

Thinking that I had some bad connections, I focused on a fuel issue with weird RPM thing. I took the carb off, opened it up.. Cleaned it out (rebuilt 20 hours ago). Checked all the jets..compressed air and carb cleaner. I assumed that the seatow gas left in the tank (Florida heat) turned to water.

Today I hooked it up on a remote tank and the same thing happened. It screamed to 4k..then got less...less.. and by the end of a 3 minute drive it would only be happy at 2900 rpm..or it would start cutting out until I backed off on throttle. By the end of the quick drive..the volt gauge was at 9..and the tach was doing the same thing when I used anything with power.

I obviously have a bad alternator (10 volts when running..batteries, switch, and alternator itself). Can a bad alternator cause the low weird RPM thing I'm seeing? Could the Thunderbolt IV be bad with the sea water splash that hit us?

I am out of ideas. I just spent $9k in the last 3 months and know this boat pretty well. Its a very odd problem. It was running very very well before the out of gas scenario.

Thanks again,

Joe

Baja 232
496 Carb Stroker

Get your voltage issue fixed first....you need to have a steady voltage to troubleshoot the engine issue. It sounds like an ignition issue to me but I would make sure my charging system was correct first.

Start with electrical as stated above, that wave over the back could've toasted an alternator or something else. As for the RPM's dying, I had a similar issue with a vac sec carb, it ended up being a stuck float.