Starting problems when in water

"Hi all,
I have a crazy pro

"Hi all,
I have a crazy problem. I have a 165 mercruiser, and each time I put it in the water, it suddenly is hard to start. I can eventually get it going, but the idle is rough and it wants to die on me. By playing around I can get it moving and run it for a while. When I slow down, it usually stalls, and then it's very hard to start. What makes this insane is that when I attach a hose to it in my drive, it'll fire right up with no problem and run fine. I do hear a "sucking" air noise when I push the throttle forward. I've rebuilt the carb, changed points and plugs, impeller, new ignition, new fuel filter. I just can't figure out why it runs so rough when it's in the water. Any help or advice would be greatly appreciated!!"

"Robert: Fuel could be draini

"Robert: Fuel could be draining out of the carb bowl when you are on the boat ramp.

Did you set the points dwell with a meter or feeler gauge? Reset the timing after the points were installed? How old are the plug wires? The distributer cap and its gasket and rotor okay? No corrosion or carbon tracks in the cap that can cause intermittent misfiring? Is the cylinder compression reading above 100 psi and similar between them--no one cylinder with a big difference?

To check for a vacuum leak, start the engine with hose/muffs and take a can of carb spray cleaner and spray around the carb base in short sweeping bursts--RPM increase spells vacuum leak. If no leak is detected, try the following:

To find out if you have a moisture related spark problem, take a sprayer bottle with tap water only in it and spray the plug wires one at a time along its length. If it starts to miss, you found one bad wire. Dry it and check the others or replace them all.

Spray the dist. cap and coil area the same way. If it stumbles, cap or coil and/or wire are suspect."

"Guy
Thanks for the info. I d

"Guy
Thanks for the info. I did check the carb and found a small leak around the gasket between the top and bottom. I replaced that last night but it got dark and had to quit. I'll try the spray bottle misting on the spark plugs wires, dist cap and coil this afternoon after I get the carb back on and readjusted. I'll keep you informed.

Thanks!"

"Guy,
I fixed the leak in the

"Guy,
I fixed the leak in the carb and sprayed with starting fluid and no change in the idle. I water sprayed all the wires, cap, and coil, and again no change. I'm wondering if the leak I had in the carb would've caused too much air to be sucked into the carb, and after finally getting it started in the water, it just wasn't getting the right combination after running it? I can only check it when it's actually in the water to see if this fixed the problem.
Thanks again for you help and if you think of anythng else don't hesitate to give me a suggestion.

Bob"

Robert: It sounds like you fi

Robert: It sounds like you fixed it. The size of the gasket leak you had was preventing the engine vacuum from drawing fuel from the carb. Good work. It's great when you do it yourself.