No idle while in the water - it just dies - '74 Merc 1500

[ZmOz]

I'm really getting close to selling this boat. I just got it about 2 weeks ago...my first boat. Thought I had all the problems fixed, I guess not. Anyway, my '74 Merc 1500 idles great at 1000RPM on land hooked up to the hose. I took it to the river today, while it's in the water it won't idle. I have to have the neutral idle about half way up just to keep 1000 RPMS. I took it home, put a big tub of water under it, idles just fine. What the hell?

 

[Trent]

Re: No idle while in the water - it just dies - '74 Merc 1500

VERY COMMON....problem. Time to remove the carbs and install overhaul kits. Clean very well with carb cleaner. And when your done........Clean AGAIN!!<br /><br />Your engine runs good on the "hose" because it does not have back pressure on the exhaust system. You must adjust the idle mixture on a fully warmed up engine and in gear...And not at the dock.