75 mercury 850 weird issue and noise

[justtwistit]

Ok so I have a 1975 merc 850 85hp outboard that has problem that I can not figure out.
Motor has 150psi in each cylinder and nice blue spark to each plug (checked using a Briggs and Stratton spark tester).
The boat runs great when I first back off trailer and drive around. When I stop at island to swim and play around for about an hour or so the boat when start fine and idle. The issue is that when I go to click into gear the boat will bog down and die. Sometimes when its about to die it will nake a horrible squealing noise like belt or bearing. When that happens the engine bogs down and dies. I can restart with no issue and it will idle at about 650 rpms. I have to play with throttle lever and main lever to get the boat going again. Once I'm in gear and driving I have no issues. I can come back down to idling while still in gear and the boat will just run right along.
I have rebuilt carbs, changed plugs, rebuilt fuel pump, changed fuel line on motor.
As far as the noise I believe it is coming from the distributor. I think the bearings might be binding up when hot but it only does it at idle never under way.
If there is any more info I have give let me know and thanks for the help.

 

[Chris1956]

Agreed, since that motor has a distributor, the bearings may be going bad. They are replaceable, but the distributor needs to come apart, and it is not obvious how. I would recommend a factory service manual.

As for the stalling in-gear, that is very common. It is usually dirty carbs, incorrect idle mixture adjustment or idle speed too low.

 

[justtwistit]

Ok I soaked carbs in carb cleaner bucket for a few hours and then rebuilt with new gaskets float and needle and seat. I have both needles set at 1 1/2 turns out. The tach reads between 600 and 700 rpms
when idling in gear. I will try to readjust the needles to see if that makes a difference.

As for the distributor I will see if I can find some one to help me as I looked on line and they used a special wrench to hold rotor shaft to remove nut on other side of housing

 

[Chris1956]

I took a distributor apart, just like the one you have. It required no special tools, Unfortunately, I do not remember much more about it than that.

Good luck.

 

[justtwistit]

Ok so update to my issue incase someone else is having similar issues. The bearings in distributor was bad, really bad. It actually ground into housing.
Bought a new cdi distributor housing to be safe since that was original trigger. I have ran in test tank for 15 min while setting timing and everything sounded and acted fine but have not open water tested. I hope to do that this in the next couple of weeks when I get more free time. I belive the bearings were the underlying issue to all of my problems

 

[sutor623]

Cool man! Im surprised CDI makes aftermarket parts for these old mercs. Id say you got lucky on that one. I had a '67 4 cylinder 650. That thing ran like a MONSTER. But if I had to replace just about anything on it, parts were nearly impossible to find, and I pretty much had to buy used. WWW.oldmercs.com had some stuff for it though. Good luck!