I have a single HP500 carb that won't idle in gear worth a crap. In neutral it idles around 1000 rpms.. Put it in gear it tries to idle around 800 rpms and dies... It makes me look like an idiot in front of the chicks.. The engine runs great besides this.. Any sugestions!!

Is there something wrong with the carb? I did put a crossover on and it runs really cool..

check the float level on the side of carb when idleing (holley). it should be trickling out a little when you remove the screw if not you need to adjust with the screw on top when idleing. you might be getting enough gas to idle but not enough to go unless you give a little throttle.

OK...been in the exact same spot before......heres some of the culprits i have found.....Check float level as seahawk mentioned.....make sure timing is right on......see if you have a vacume leak anywhere........make sure the coil is good (it still may run with no load but once engauged it died and coil was shot)......see if the mechanical advance under distributor rotor if working properly(i had one spring on the MSD break and it still worked but just like above)

Make sure you check the fuel bowl float levels with the boat IN the water. The angle sitting on the trailer could be qiute a bit different.
Did this just start after you installed the cross over???

A few other things to check would be to make sure the carb is clean, just spray some carb cleaner down the air bleeds to make sure they are clean. Also check to make sure the butterflys are open the same amount. If your primayr butterflys are open further than the secondarys it can run rich, and load up and die when you put it in gear. This sounds like your problem

I'm pretty sure your flux capacitor isn't making the 1.21 jigawatts of power necessary to let your motor idle.

Sorry, been feeling like crap all day, finally feeling a bit better.....so there you go.

The ignition module on that motor keeps your base timing @ ? and keeps the idle at a fixed rpm (I'd have to look it up can't remember) that is why you have to ground out the wire in the back of the motor when you set the timing so it doesn't try and keep locking it to base. Sooo with that said it could be a bad module. Or any of the above.
I don't know that putting on a crossover on that motor with that type of merc module was the best idea. You are now running too cold and may have some hot spots (steam) that could cause more harm than good. Just my .02 I could be way of base!

I had the same problem (times 4) the idle circuit may be just running to lean or rich. If holley design, the idle screws sould be about 1 1/2 to 2 turns. I was just running too lean.

Power valves are also a potential problem. If you screw in the idle screws all the way with very little change then it may be a power valve.

Check timing, float level, and ignition as everyone stated above. You sould be running within a day.

Good luck.

I had the same problem and it was crap in the gas that even got by the filters. Stuck a couple of $5.00 inline filters in right before the fuel intake and fixed it. What was going on was the junk in the gas was getting stuck in the needle and seat, causing the boat to flood and die.

Good luck!

Mongo

I had same problem, flame arrestor was dirty, cleaned it out with carb cleaner, let it dry completely, put it on, problem fixed. Cut down on some of the black soot on the transom also.