Merc 50 hp bogs down under load

[dgm]

I have what I believe is a 1967 Merc 50 HP four cyl. It has been sitting for a while in someone elses garage so I'm not sure of its history. Serial No# 1770362. Compression is 120 in 3 cyls and 110 in the other. It starts ind idles fine and revs great when its out of the water. When we take it to the lake it stalls when you put it in gear. We add a little fuel with the low speed idle and that helps then it wont go to full rpm with WOT. It has new plugs and fire to all at idle. What should I check? Thanks Dave

 

[JB]

Re: Merc 50 hp bogs down under load

Howdy, DGM.<br /><br />You are almost certainly running on two or three cylinders. Most engines can do that with no load and sound fine.<br /><br />Crank it up on the earmuffs. one at a time pull or short out the plug wires. If there is no change, that is a dead cylindwer. If it is a cylinder making power rpm will drop.<br /><br />Check any dead cylinders for spark. If they have spark, spray some premix into the carb that feeds that one. If it picks up you need to overhaul that carb.<br /><br />Good luck

 

[dgm]

Re: Merc 50 hp bogs down under load

Thanks JB, I'll get back to you with the results.<br /><br />dave