Logo
FULL SITE MENU

1979 Mecury 500 50hp

N

n1c02

New member
I just bought a 1979 ranger bass boat with a 1979 Mercury 500 50hp thunderbolt outboard..... the motor runs good and idles... the issue I am having is that even at full throttle it isnt going at full speed or full throttle.. I was told htat it needed an adjustment to make it able to go full throttle.. can anyone help me with this?

Thanks
Terry in Ohio
[email protected]
 
I was told htat it needed an adjustment
Click to expand...
If that was the case then why didn't the SOB make it? First thing to do is get a service manual. Verify the carb throttle plate opens fully. Check for full spark advance. You are probably going to have to rebuild the carbs.
 
Check the compression and check to see if you have spark at all 4 cylinders.--------They will run quite nice on 3 cylinders.
 
racerone said:
Check the compression and check to see if you have spark at all 4 cylinders.--------They will run quite nice on 3 cylinders.
Click to expand...


Thank you.. they said something about the butterfly choke or something. but your advice sounds more promising.. thank you..

Terry
 
they said something about the butterfly choke or something.
Click to expand...
That is the throttle plate that controls the amount of air ingested w/the fuel. Racerone is right about it running on 3 cylinders. Look at the spark plugs and post pictures of them...keep them in a line corresponding to the cylinder they came from so we can see what each cylinder is doing.
 
From the look of the plugs the #3 cyclender is foulin out some. A compression test of the motor should be done to see if all the cyclenders are up to spec. If the carbs have been worked on, the very small key in the top of the carb link from the top carb to the bottom carb might have got lost and will not open the bottom carb. It will cause the motor to run lean on fuel and can burn a piston. The bottom and top carb should open the same when the throtal is advanced. With the motor shut off and in FWD watch that link as the throtal is advavanced to the WOT and see if the link moves the bottom carb the same as the throtal is advanced. If it dose not move the same then that tab is missing and new one will be needed. The tab can be bought or made from a feeler gauge cut to fit the link. JMO
Oldman570
 
i got the ranger boat for 500.00 was told that the throttle needed adjusted to allow it to go full.. so not sure.. never messed with it.. still wishing it had tilt/trim.
 
You might try adjusting #2 carb a 1/4 turn CW, run the engine for a while and recheck the spark plug burn pattern.
 
Back
Top