4.3 alpha one first gen won't go over 3500 rmp under load.

[crashnburn98]

I have a 4.3 alpha one first gen with the mechanical fuel pump. Boat sat a few years. Got it running, new fluids and filters. Put the thing in the water wouldnt run. Rebuilt the carb and changed fuel pump. Ran good for a few hours than acted like low on gas. Had a half tank still. Checked the filter in tank and the siphon valve on tank all good. Switched to my 6 gallon in boat tank just for fun, no difference. Got a new carb, checked all filters, nothing in them but clean gas. New spark plugs. Thing seems good from tank to crab but won't open up under load above 3500 ram. Distibuter looked clean inside. Didn't move it just took cap off and used some 1000 grit to touch up the tips on cap carefully no difference. Wire to coil seems good. Gonna check timing with a timing light next, any other ideas?

 

[Bondo]

Ayuh,...... Welcome Aboard,...... It's usually a fuel system problem, but it appears ya covered that pretty well,......

I guess, I'd run a compression, 'n leak-down test on it,........

 

[Rick Stephens]

You don't say what year, might post that and serial number. I can see timing being a possible culprit as well. I don't think the 4.3 ever shipped with points..... so Thunderbolt 4 ignition?

 

[Spidrmunky]

I had that problem and the oil level was too high from a dealer mistake. They suctioned the oil from the dipstick tube, thought they got it all, then added 3.8L of oil to the 2L left in it. Checked everything gas and timing related and ended up being oil level because my plugs were soaked. Just trying to offer a simple solution. Hopefully not something serious and hope you find a resolution.

 

[crashnburn98]

Points was a bad choice of words. I just meant the contact on the distributor cap. It has the thunderbolt 4 ignition system with the timing module mounted on the cooling header. Engine serial number is 0c526017 drive is 0c641521. Its a 1989 17 foot Thundercraft with the 4.3 /v6 alpha one. I'm gonna check the compression in the next few days and see if I can get a timing light to check timing as well. Dont think it has a compression issue though.

 

[crashnburn98]

I checked the oil level and quality multiple times when it started acting up. All good, had just done an oil change on it as well so oil and filter are new. Hoping to check compression and timing in next few days....

 

[crashnburn98]

OK guys figured it out, rocker on cylinder #1 not moving. Guess I'm tearing the engine down.

 

[Rick Stephens]

OK guys figured it out, rocker on cylinder #1 not moving. Guess I'm tearing the engine down.

Ouch! Let us know what all you find.