74 Merc 850 Questions

[Yammerhead]

I have a new to me 850 that I have been trying to get working properly and have a few questions.

First of all, the biggest issue is the gear engagement. I can set the linkage so it engages well in reverse or forward, but not both at the same time. When I set it to try and have both reverse and forward, the prop staft bangs on the clutch dogs. I got mad and set the linkage so the shift rod turns further in forward and took the boat out. I works great, engages quickly and does not slip. Pulled the kids on a tube and it worked quite well. Before I tear into the lower unit, I thought I would ask if there could be any other issues that could be causing this. The only other thing I can think of is the control unit. Is it common for the cams in them to wear out and not have enough travel to turn the shift rod far enough? Looking at the Clymer manual, it didn't appear to have any adjustability?

What is the proper idle speed? The manual made a generic reference to 500 to 650 RPM. I set it down to about 800RPM and it dies when you go to engage it now. It was set at about 1100 RPM and worked OK. I thought I would ask the proper speed before changing carb settings.

What is the proper charge voltage? My fish finder reads 16.8V at cruising speed. Seems kind of high, and I am wondering if the voltage regulator is starting to crap out?


Thanks!!

 

[Chris1956]

Re: 74 Merc 850 Questions

Yammer, The MerControls usually have plenty of travel for the gearshift. Unless yours is damaged, you need to make sure the shift cable is adjusted properly. Unclamp the shift cable. Set the motor to neutral. It will stay in neutral on a detent, if the LU is working properly. Now adjust the barrel nut (control in neutral) to fit the clamp. if this doesn't solve the issue, you might try another control.

You will never get 650RPM in gear, in my experience. Just set it as low as possible. (~750-800) Only use the throttle cable barrel nut and the idle stop to change the idle speed. Don't mess with the idle pickup timing.

That motor does not have a voltage regulator. It uses the battery to absorb any excess current, and as such you will see a high charging voltage. Since the stator only puts out about 6Amps at high RPM, it is not usually an issue. Keep the battery filled with water.

 

[Yammerhead]

Re: 74 Merc 850 Questions

I played with the adjustment barrel quite a bit. It was quite sensitive. One or two rotations would make a big difference on how well it engaged into gear. The lever on the control has a fair bit travel after engagement to where the throttle starts to pick up. I will have a closer look at it before I go and tear into the gear case.

 

[Yammerhead]

Re: 74 Merc 850 Questions

Well, I pulled the control apart and I think I found my problem. The shift lever is worn and doesn't actuate the cable far enough. Particularily in reverse. Hopefully a new one will give me reverse back again!