Reply With QuoteFloats adjusted and accelerator pump diaphraim brand new.
I have a 1978 460 ford motor jetboat that dies after a short time. It will start up fine and I can take the 5 year old granddaughter for a run so she can see my "turkey tail" run and then the engine will act like it runs out of fuel. I can immediately start up again. I had a friend check the carb while we ran and he said there was fuel the whole time. I idled in the water and took the motor up to 3000 rpm and it ran fine until that point. I did this over and over and the same result. As long as I don't go past 3000rpm I'm fine. Doesn't do it in the driveway. Also the vacuum secondarys stick. I have rebuilt the carburetor and checked linkage. It doesn't do it with the motor off. When I manually work the actuator rod it doesn't want to go back down completely, I have to pull it down. Finally, my amp guage is showing a negative charge. I checked wiring and found a disconnected wire (field?). Connected it back and no change. Used a handheld little alternator checker with a probe and alligator clip to ground and it showed ok. Any help is greatly appreciated.
Floats adjusted and accelerator pump diaphraim brand new.
These symptoms could point to a number of things.
If you are running a points distributor, I suggest you change out your points and condensor. I'll bet that either the rubbing block has worn down on the points and the gap has closed between the contacts just enough to cause your symptoms, or your condensor is failing. The condensor failure is an often overlooked/hard to find failure but your symptoms match it perfectly.
The lack of charge may not be related; check grounds.
In regards to your symptoms and the relevance to fuel delivery: check for water in the gas...in the fuel tanks and the float bowls.
That ought to be a good start in your diagnosis....
LO
Some vac sec carbs have a "check ball" in the vacuum housing base to prevent sticking. Pull the top off and look to see if there is one in the vacuum port.
You might hook up a fuel pressure gauge and check how much pressure/drop there is from your pump before and after your 3k threshhold.
Lakesonly I will do what you say. It is an Accel dual point distributor and I haven't replaced the points or condenser. I looked at the points but that was it. There is no water that I can see and I do have a water separator. Rootswear, I have the checkball in place. Anyother ideas? Thanks to all for your help.
I have had a bad coil that behaved the same way, till it got worse, and the RPM break-up point went down.
Would run great, till it got hot, then would refuse to run above a certain RPM, untill shut off long enough to cool significantly, then was fine, untill heated again.
I have a new coil I'm also going to use. I had a helper check the coil for heat and it wasn't hot. But it can't be that because the boat will start up immediately. As long as I don't go above 3000rpm I can run all day. It doesn't do it in the driveway. Just under load.
I have a new coil I'm also going to use. I had a helper check the coil for heat and it wasn't hot. But it can't be that because the boat will start up immediately. As long as I don't go above 3000rpm I can run all day. It doesn't do it in the driveway. Just under load.
That is EXACTLY how my coil acted, for the first 2 days.
I cannot tell you how "hot" the coil was, because I never grabbed it, but the internal heat or whatever was causing it to break down and miss-fire like it hit a rev-limiter.
Use a jumper from + battery to + coil, just as a test......Fixed? go back towards the switch, as in switch side of the ballast resistor, still OK...Kepp chasing it back towards the switch until it fails.....OR hot wire = no difference, now you know it is down stream from the 12v to the coil and can work from there towards the spark plugs.................MP
" Friends don't let friends drive Fords "
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