Merc Engine Dies Out During Acceleration

[JLehmus]

Hello,<br /><br />I have a 40hp 1980 merc 2 cylinder outboard. It had been winterized in 1999 and then sat covered and outside until last fall.<br /><br />It always starts right off, idles fine and I can troll for hours. If I slowly accelerate, I can move along at about 10 mph and everthing sounds normal. <br /><br />As soon as I try to accelerate to full speed, it acts and sounds like I am dragging a dock or two, and the engine will die out, if I try to push it.<br /><br />Plugs, gas tank line & fuel filter were replaced so far. I also bought a repair manual and a VOA test meter.<br /><br />What would you do, to get started trying to diagnose this problem? Do you think it is fuel or ignition related?<br /><br />Thanks in Advance,<br />John<br /><br />d:-]

 

[JB]

Re: Merc Engine Dies Out During Acceleration

Howdy, John.<br /><br />The first thing I would do is determine whether the problem is fuel, compression or ignition related.<br /><br />Squeeze your primer bulb when the engine is misbehaving. If it picks back up, you have a fuel starvation problem. <br /><br />If not, you are running on one cylinder. With the engine idling, pull the plug wires, one at a time. If the engine doesn't respond that cylinder is not making power. If it slows or dies that is a good cylinder.<br /><br />See if a dead cylinder's plug wire will arc to the block. <br /><br />If it will, you may have a bad reed or you may have lost compression on that one. Do a compression check, warm. Each cylinder should compress over 90psi and the two should be within 15% of each other.<br /><br />Good luck, and let us know what you find.

 

[sho305]

Re: Merc Engine Dies Out During Acceleration

I go after the fuel system first as storage makes this a popular problem. You can pull the lines off the carbs and use the bulb to check for restriction, then squirt fuel in the carbs while running to make sure its getting to the motor if you can *safely* do so as a last resort. I clean the whole fuel system, install new plugs and impeller with any unknown motor just to start with, and that eliminates most problems. I use dielectric compund on all spark plug boots/connections to waterproof them also. A $3 tube lasts forever and the boots slide right off. Another quick tip is if one cylinder is dropped, it will have a cooler spark plug after running a few minutes.

 

[JLehmus]

Re: Merc Engine Dies Out During Acceleration

Yeah Rah Rah<br /><br />It was ignition to one of the cylinders.<br /><br />Pulling the plug wires one at a time did the trick.<br /><br />I took her out yesterday and she flew across the water.<br /><br />Thanks,<br />d