85 hp mercury wont accel

[The Rocketman]

My 1976 85hp outboard Mercury wont accelerate in gear. When it is in neutral, it will rev up fine, but in gear once it gets to half way it stays there. Could it be the throttle?<br /> Please help,<br /> Rocketman

 

[Barnacle_Bill]

Re: 85 hp mercury wont accel

Check your manual and do a link and sync to be sure the throttle is opening up all the way. If that is good check fuel vent, all fuel lines primer bulb and fuel pump in that order. You may not be getting enough fuel to operate it under load.

 

[dreamboat]

Re: 85 hp mercury wont accel

I am in the same boat. Will have a Merc mech. water trial this in a day or two. 2nd time in shop for this problem this month. I have rebuilt the fuel pump, carbs and replaced bulb and new glass barrel strainer. Something needs to happen.<br /> Will fwd info to you.

 

[700XC]

Re: 85 hp mercury wont accel

make sure all plugs are sparking , new plugs ans see if you have spark on each one.<br /> One dead plug or coil will rob a lot of power from your motor unde load.<br /> also if you have cdi ignition the switching box can go bad, used can be a few hundred $$ but check your spark plugs first.

 

[dreamboat]

Re: 85 hp mercury wont accel

At this point the new Mercruiser power pack was defective, the stator had gone bad since being tested 3 weeks ago. These were replaced. The coils check out OK. The carbs were disassembled and reassembled.The idle was set to 1200 rpm out of necessity, its not a new motor. It would idle at a lower setting but die when put in gear. <br /> The timing was moved a very slight amount and that seemed to help. The marks on the flywheel are scratched up more than likely from trying to pull start the motor some time ago so we were hesitant to move the timing very much without some tech. help.<br />One jet was .010 over size.<br />The whole thing seems to center on the induction reeds and the compression. <br />We did have some luck getting past the mid-range stall with the timing advance and not using the choke to power through this stall phase.<br /> How this motor will run in a shop is not how it will run on the water so be sure and test it on the lake. <br />good luck.

 

[JBL]

Re: 85 hp mercury wont accel

I have a 1984 75hp Mariner that used to do the same thing. heres what happened. I ran the motor in the dark with the cover off. Man, it looked like Bahgdad during Desert Storm. Sparks were jumping all over. I put new wires on and it got better but not complete. Sparks were coming out of the boot down to the block. I put dielectric grease in the boot and now ever since it has been running like my Toyota 4runner.<br />Like a fine watch. Run the motor in the dark.

 

[tompowers85]

Re: 85 hp mercury wont accel

I am having the same problem, so if you figure out the problem please let me know. I took it to a mercury repair shop and they said thew will not work on a motor that is so old.

 

[dreamboat]

Re: 85 hp mercury wont accel

After a large personal commitment of time and attention by the Service mgr. he found that the idle had to be set separately and somewhat differently on each carb, a larger jet in the upper carb. He also found from Mercury the timing and the advance timing were way off. The timing marks were scuffed off the flywheel by someone using the rope start and it made it tougher but he got the timing procedure and used a light and measured TDC and got it straightened out and running.<br />This motor was tinkered with before I got it by some knothead that failed to have the expertise to diagnose the trouble and therefore made the wrong adjustments and had it screwed up good.<br /> The idle was backed down to more reasonable rpm's and idles pretty nicely.<br /> IT accelerates very well right off the trailer and goes through he mid-range bog down right to 5000 rpm. It backs down when the throttle is decreased and doesn't die and will pickup and scat again as intended.<br />All in all the reeds may be a little weak and the compression giving up a little but the motor runs well, starts and goes when it should.<br />Good luck with yours.

 

[tompowers85]

Re: 85 hp mercury wont accel

Thanks, I am going to be putting mine in a test tank and doing alot of what you just wrote. I am going to have a guy who does engine work on the side look at mine. Thanks alot.

 

[shipoffools]

Re: 85 hp mercury wont accel

IBNFSHN mentioned right off the bat to check your manual. I could not agree more. If you have been lucky enough to find a service man who will look at your old 3 banger with compassion it is a rare find indeed. Where I come from most shops see my old 70hp as an opputunity to sell a new motor. <br /><br />These engines a pretty easy to work on with some basic skills, tools, a good manual, and most of all assistance from some pretty knowledable guys on this forum.