I have a 1979 Glastron CV23 w/460 Jet. The boat is 100% stock with about 75 hours on it since new, was in storage for a lot of years. I buy the boat and change out the 12 year old gas, rebuild the Holley 650 Vac second carb. The inside and outside of the carb still looked new, but I still put a kit in it. I took the boat out and it ran great except for strange problem with the idle. When I would take the RPM's up to when the secondary kicked in and then return to and idle the rpm's will stay about 2000. I then removed the throddle cable and the idle stayed the same so it's in the carb. I checked the idle stop screw and it was closed on it's stop. Now here is where it gets strange, if I just turn the motor off and restart with out doing any thing else, it idles normal. It would seem that the secondary butter flies are sticking or some how the vac pull off is still pulling vacuum?
The second problem is I was run back to the ramp at the end of the day and around 3000 rpm and it acted like I was running out of gas, the engine died, I restarted, run a few minutes longer, then did the same thing, so I restarted again then just idled back to the ramp area which took about 30 min. Do you guys think that since the fuel pump is about 30 years old that it's going out or could it be a plugged pickup in the tank. I was thinking that I should replace the mach. pump with an electric one? If I go electric, which pump would be best and how are they wired into the boat? Thanks for any and all help!!!!
There is an idle screw on the secondaries, not readily accessable and it has it's own built in return spring. The fact that it idles when it has been sitting, says that the spring is probably dirty or has come off the little pin that holds it in place (and that you don't need to touch the secondary idle speed setting). Take some carb cleaner and find the secodary spring. It is on the opposite side of the throttle cable on the secondary shaft.
Holley secondaries are not directly linked, and are more designed to open positively rather than close 100% - the spring is supposed to take care of that. After cleaning it, make sure it is clipped and providing closing force.
I would change the filter first, it does sound like the carb is running out of fuel, or you were experiancing vapor lock (uncommon on a boat). Mechnaical pumps like to suck, electrics like to push - so if you get an electric get it as close to the tank as you can. I personally like the Mallory comp 140, it is quiet and flows enough for 800 HP. Obviously it is inherently more dangerous, as if something happens you will have fuel spilling out into your hull. This is the reason I will only run a mech on a boat while all of my racecars get nothing but electrics.
To make it a little safer, have a manual switch to be able to shut it off, and get a remote fuel pressure gauge. That way if you see something wierd you can kill it and check it out beofre you have 10 gallons of fuel sitting under you.
The other danger is that if you stick float in the carb - with a mechanical the engine will die and the fuel will stop as the carb venturi fills with gas and then overflows. With an electric, it just keeps pumping fuel out and onto the engine. Really dangerous normally, deadly if you have a cover.