1985 Black Max idleing problem

[sdyarman]

My 85 black max will run perfect anything above idle i have elimenated the fuel system this is not a fuel problem. This problem started while i was doing some trolling. It will idle for a while when i first start it but then it just dies if i bump the throtle up to about 1000 rpm it will stay running. When it dose stay idleing it is rough and rpms go up and down some i did replace the spark plugs first thing i tried.I put new plug wires on over the winter. Thank you for your help in advance.

 

[Lando]

Re: 1985 Black Max idleing problem

You said not a fuel problem...only suggestion I have is to run a can of Seafoam through with 1 gallon of gas (very rich) to decarb. Run it through, let it sit about half an hour, then restart and run with regular gas. Expect a lot of smoke.
Doing this solved similar issues I had with my 95 Black Max (175). It wasn't starting without throttle help & was idling rough. Doing the above took care of both for me.
Good luck.
JL

 

[Kev144]

Re: 1985 Black Max idleing problem

Your having a similar problem i had on my 89 Black max 150. It would idle ok above 1000 RPM but when put in gear would stall out at idle. Turned out to be a stator. They have 2 plates on them one for idle RPMs and higher. One side can burn out which was what happened to mine. I would check the voltage coming out at idle and see.

 

[TommyA]

Re: 1985 Black Max idleing problem

Kev144 what would be the voltage reading at idle, battery voltage? I am curious how this effects the idle.

 

[Kev144]

Re: 1985 Black Max idleing problem

Kev144 what would be the voltage reading at idle, battery voltage? I am curious how this effects the idle.

I'm not suyre on the voltage reading, i had a friend do it for me as the boat is 2 hours away from me currently. Basically what I was told that it isnt putting out enough power to the switch boxes. So one side (3 of the 6 cyl) isn't getting enough power to the spark plugs and so when putting it in gear, when under load doesnt have enough power to stay runnuing. Something along the lines. I'm not a big out board guy as we mainly focus on big I/o's. We currently have a boat with triple 1075 CI motors. She's a beaut though

 

[TommyA]

Re: 1985 Black Max idleing problem

Thanks Kev, that would make sense. I think that would be almost impossible to verify while it is running so a check on the stator themselves would most likely show a short.

 

[jkering66]

Re: 1985 Black Max idleing problem

Hello,

Post how this troubleshooting works out. My 1988 175 Mercury is doing the exact same thing starting this year. Have not gone fishing due to cannot idle/troll at a slow speed.

Worked on the boat last night, idle at 1000 rpm and above, runs fine. Put in netural, motor sounds like it has a cold, shiver, shiver, sputter, stall. Put into gear, stall, but if you put into gear very fast from fast idle and get up over 1200 RPM, runs great.

I think, not positive, as it was warming up it was fine, got up to temp, shiver, shiver, stall in netural, could have been my imagination.

I pulled the bottom carburator to take a look and it is very very very clean, so I did not pull the other carburators.

I will also try the Seafoam clean out.

Thanks

 

[Kev144]

Re: 1985 Black Max idleing problem

Hello,

Post how this troubleshooting works out. My 1988 175 Mercury is doing the exact same thing starting this year. Have not gone fishing due to cannot idle/troll at a slow speed.

Worked on the boat last night, idle at 1000 rpm and above, runs fine. Put in netural, motor sounds like it has a cold, shiver, shiver, sputter, stall. Put into gear, stall, but if you put into gear very fast from fast idle and get up over 1200 RPM, runs great.

I think, not positive, as it was warming up it was fine, got up to temp, shiver, shiver, stall in netural, could have been my imagination.

I pulled the bottom carburator to take a look and it is very very very clean, so I did not pull the other carburators.

I will also try the Seafoam clean out.

Thanks

Have someone test your stator. Mine was doing this exact thing. 89 black max 150. Would idle and run perfect above about 1300 rpm. Idle or idle in gear below that it would just stall out. Replaced the stator and ti runs like a charm.

 

[j_martin]

Re: 1985 Black Max idleing problem

My local OMC mechanic tells a story about a big engine that wouldn't idle in the spring. He finally decided to check the reeds and found a petrified mouse stuck in one of the reeds.

One thought, though. I used to train computer field engineers, and the hardest thing to get into their heads is this:

If you walk up to a running machine and do something to it, and it now does not run.

IT'S WHAT YOU DID!

That said, the likelihood that some little maintenance thing you did over the winter backfiring is high.

hope it helps
John

 

[jkering66]

Re: 1985 Black Max idleing problem

I replaced the Stator on my 1988 175 Merc, fixed idle problem, idle and runs great.

It did introduce a new issue, probaby related to the stator replacement:

Quite a few times a day when I am out on the boat, 5 times Saturday, the RPM will shoot up to 5000 to 6000, even though I am at 2500 crusing speed and dont speed up.

So the engine thinks the boat is going 5000 to 6000 RPM, but I am at a steady 2500 RPM, and the engine runs bad when this happens, the engine thinks it is at 5000 or 6000 RPM, then after a minue it gets over it and goes normal.

Am I getting some type of arcking on the connections, this only happens about 4 or 5 times when I am out for a few hours.

Thanks

 

[j_martin]

Re: 1985 Black Max idleing problem

I gather the engine isn't actually revving up, but the tachometer reading is going up.

Check all your connections, especially the stator connections to the rectifier or regulator. If they are all good, and if the engine actually misfires, I would bet the new stator is arcing internally.

hope it helps
John

 

[j_martin]

Re: 1985 Black Max idleing problem

I gather the engine isn't actually revving up, but the tachometer reading is going up.

Check all your connections, especially the stator connections to the rectifier or regulator. If they are all good, and if the engine actually misfires, I would bet the new stator is arcing internally.

To help clarify, the tachometer runs off the charging circuit. The engine runs off seperate charge coil circuits. They do not have anything in common except the mechanical sharing of the stator core.

hope it helps
John