1986 Mercury 60 Bogs/Dies at Mid-Range, OK at Idle-Full Throttle

Hello everyone, I've got a tricky problem I've been fighting with. Last season my motor (1986 Mercury OB 2-stroke) wouldn't run under any load when I de-winterized it. I cleaned the carbs and everything was great. I replaced the fuel filter and plugs at this time also.

Gradually as the season went on my mid-range power got worse and worse. What started out as a slight flat spot gradually turned into a complete bog/die at any speed other than full throttle or idle.

Towards the end of last season as a last-ditch effort I replaced the fuel lines, gas tank fittings, fuel primer bulb, fuel pump diaphragm, fuel filter, and spark plugs. It made no difference. I also drained the gas and put fresh stuff in there, still no difference.

Any ideas? I'm a DIY on a budget so I'd really hate to bring it to the dealer. Thanks in advance.

Re: 1986 Mercury 60 Bogs/Dies at Mid-Range, OK at Idle-Full Throttle

I think u may have the same prob that I got . I gave up trying to figure it out on my own, finally broke this morning and decided to get off the money so I took it down to the beach to the Marine Service Center so I should know whats going on and what it's gonna cost me in a few days, when I find out I will post what the heck is going on. I just couldn't get it figured out on my own , so I broke.....ready to ride u know.Check my thread for the update, good luck..

Re: 1986 Mercury 60 Bogs/Dies at Mid-Range, OK at Idle-Full Throttle

I'm going to do my best to stay as far from the dealer as I can. Plus, I doubt they'd want to touch a 1986 anyways. I hav a sneaking suspicion its the carbs again...

Re: 1986 Mercury 60 Bogs/Dies at Mid-Range, OK at Idle-Full Throttle

Mercury60 said:

I hav a sneaking suspicion its the carbs again...

Click to expand...

BINGO!!!!

The two strokes require a FAT ide mixture, slightly more than 'Best Idle' while IN gear IN the water.

Any less and acceleration suffers.

Either you didn't adjust the idle mixture fat enough, an idle passage isn't clean enough, or a float isn't set quite right.

First try backing out each idle mixture screw the width of the screwdriver slot then retest acceleration, if betterm repeat until perfected.

Re: 1986 Mercury 60 Bogs/Dies at Mid-Range, OK at Idle-Full Throttle

Mercury60 said:

I'm going to do my best to stay as far from the dealer as I can. Plus, I doubt they'd want to touch a 1986 anyways. I hav a sneaking suspicion its the carbs again...

Click to expand...

Mine's an 85 and the dealer took it in , I just told em that I'm not trying to put a ton of money in this motor so they gonna see what the prob is and call me before they do the repair. Anyway, I been trying to figure this thing out a while and not getting anywhere . One mechanic suggested that he thought it was the reed valves. If it is , do u know how big a deal that is ? Anyway like I said I got iit at a very reputable dealer at the beach and I'm confident they will get to the bottom of the problem so I'll update u later.

Re: 1986 Mercury 60 Bogs/Dies at Mid-Range, OK at Idle-Full Throttle

Thanks, I'd really appreciate an update when they get back to you...

Re: 1986 Mercury 60 Bogs/Dies at Mid-Range, OK at Idle-Full Throttle

Mercury60 what did you ever find out

Re: 1986 Mercury 60 Bogs/Dies at Mid-Range, OK at Idle-Full Throttle

Old thread but if anyone is reading this. I had the same problem.

The major culprit was dirty fuel lines, dirt in the fuel filter, and varnish in the carb. I flushed and cleaned it all and the engine never bogged down again.

However, it was only firing on one cylinder, not getting spark to the bottom cylinder but sounded fine, just low rpm. I found that was a switch box issue. Changed the switch box and now the motor performs great!