Problems with '76 Merc 85hp

[reschler]

This is my first experience with outboard repair. I have a 1976 Merc 85Hp that originally had no power under load. After much reading, I determined the second carb wasn't pulling its weight. I pulled and cleaned both carbs - boom - runs wide open!<br /><br />However...3 issues remain, and I am hoping to get some ideas for each of them.<br /><br />1) The moter does not idle under load for very long. Usually dies while I am trailoring. I tried tinkering with mixture screws, but didn't seem to help. Idles fine in drive way, but under load - maybe for 15-30 seconds, starts running very rough - and dies.<br /><br />2) Out of the hole, the engine starts to bog...I tap the choke button, and boom - it takes off, and runs great. Probably not getting enough gas, but why does it run fine after a single tap of choke button?<br /><br />3) Water pump seems to work fine (good stream from pee-hole) until engine starts to heat up. Then water stream turns to a trickle. Yes - I turn off engine when this happens.<br /><br />Thanks in advance!

 

[The Marine Doctor]

Re: Problems with '76 Merc 85hp

I will start in rev order.<br /><br />Rebuild the water pump.<br />Remove and rebuild the carbs, as you say you have to choke it to get over the lean condition at idle to increase in throttle.<br /><br />At idle...does it POP and die?<br /><br />TMD

 

[reschler]

Re: Problems with '76 Merc 85hp

First off, Thank you VERY much for your help.<br /><br />3) Yes - I planned on replacing water pump, but fact that engine temperature affect it, made me a little more concerned.<br /><br />2) I cleaned carbs, but did not rebuild. Also, it was my first ever carb cleaning exercise, so perhaps I didn't get all the gunk out.<br /><br />1) A Pop? No, it doesn't backfire. It just starts to run very rough, stuggles to keep running, and finally dies. Lots of vibration on the motor (maybe all some cynlider at not firing at that time?). I can usually put in back in neutral, rev it a bit, and start the process over again (run ok for 15-30 sec, run very rough, die)

 

[bob58]

Re: Problems with '76 Merc 85hp

try turning idle mixture jets counter-clockwise @1/4 to 3/8 of a turn