Issue with 1986 supra comp--need help! thanks.

[WBLskier]

 

My friend has an old supra and his having the following problem with his boat. He had experienced some fuel delivery issues (he thinks) that he thought he had sufficiently addressed. I'd love to be able to help him figure out what might be causing this problem. Thanks in advance for any help.

 

Boat

• 1986 Supra Comp ts6m

• Ford 351 engine, 740 hrs

• Holly carburetor - It's a 4 barrel, 600 CFM, Model 4160 marine carburetor.

• 13 x 13 three blade prop

 

Issue

• Boat has recently been moved from MN at 950ft (White Bear Lake) to CO at 7788ft (Ruedi Reservior)

• It was running fine after we did some work in MN where we replaced the fuel pump, fuel filter, and removed the anti-siphon valve from the gas tank. (it was dying of fuel starvation, apparently from a weak fuel pump)

• We drove through 3/4 of a tank last weekend at Ruedi, and it died suddenly. When we tried re-starting it we ran into an occasional clicking, where the boat wouldn't even turn over.

• When it did turn over it wouldn't fire unless we sprayed starter fluid directly into the carburetor. It would die again as soon as it burned through the starter fluid.

 

[Glydon]

Did you adjust the carburetor for the difference in altitude ? If not this is most likely the culprit , might want to read this holley.com/data/Products/Technical/R7849-2.pdf good luck and let us know if it helps!

[Glydon]

Oh and btw the helpful part in that above .pdf is on page 9 re: Main jets.

[WBLskier]

he hasn't re-jetted it yet, but I think he is planning to. I'm sure that would account for loss of power, but do you think it would cause the issue he is having with it not starting as well? thanks!

[Glydon]

Have him change his jets first and fix that issue THEN if the problem persists start to troubleshoot the clicking. I am thinking he will need to adjust the timing for elevation as well, so this could be the cause of your clicking. If the ignition is not advanced enough for altitude it will cause this to happen.

[skier2788]

More important than the jets is timing of the distributor it sounds like it is too far advanced and thats why sometimes it wouldnt want to turn over. Running at altitude is a lot different. I live in fort collins so have fought these issues. I have an 86 american skier. Jets will make you foul spark plugs more than likely you have issues with both timing and fuel. I think that is the same holley as mine and they dont use jets they use fuel metering plate and fuel/air ratio is dictated by the float level in the carb.

[ToddF]

That is a huge jump in altitude, Re-Jetting and timing, does it have points? If so switch those to the pertronix setup. I would talk to a mechanic in town and ask him what size jets and timing works best at that altitude.

 

at 7700 feet that boat is always going to be way down on power no matter what you do!!