merc 800 not running right

[gakpuss]

This forum has been a great help to me in the past. I am a newbie to boating and am stumbling along. Please help if you can. I am currently having three problems with my 1969 merc 800. I am only getting about 3800 rpm at WOT, I can't get the idle in gear down to 400-500 RPMs and it bogs down and cuts out unexpectedly. When the bogging occurs at WOT I touch the choke and it recovers some but not fully. Pumping the bulb has little or no affect on the way it runs. I have done the following; water pump, new fuel tank, new fuel, rebuilt the carbs , (I found water in the carbs when I took them apart), new wiring harness, new spark plug wires, timed it and cleaned the distributor and rotor contacts. I have the service manual. I am not the best mechanic but, I can follow directions. Any ideas?

 

[Laddies]

Re: merc 800 not running right

First that engine was never designed to idle below 750 in gear when new you had a good one that idle at 600 to 650.
The lack of RPM and stalling could both be from to much prop pitch.

 

[gakpuss]

Re: merc 800 not running right

Thanks for the reply Laddies. I know absolutely nothing about props. I purchased a parts motor and its prop was in better shape so I put it on my motor. I don't know what the pitch is. What should I be looking for?

 

[Laddies]

Re: merc 800 not running right

It's impossible to say unless you know many different factors and even then it's a guess until it's run on the boat with a tachometer on it. Prop pitch is determined by several things, length, weight,hull type and the condition of the bottom. The prop on a boat acts just as rear end ratio on a truck or car, to much pitch and the engine won't be able to put the load and is low on RPM, to little pitch and the engine has lots of power and to many RPM allowing it to over rev till it self destructs. Your engine should turn 5000 to 5500 at WOT with a average load in the boat