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1970 Merc 650 - gear box removed - gear stuck in forward drive

J

Joe Baublis

Member
I removed the gear box to replace the water pump. I had removed the shift link, wrongfully thinking that it's detachment would help remove the gear box. I removed the gear box with the link detached. I replaced the water pump, and re-installed the gear box. As a test, I turned the flywheel clockwise, and I found that the propeller rotates forward only - even when the shift level is in reverse. So I pulled out the gear box, and re-connected the shift link, and re-installed the gear box. The propeller still turns forward whether the shift mechanism is in neutral or reverse or forward.

Is there a cure for this problem? :confused:
 
When you say you removed the shift link,I presume you detached it underneath the power-head.Reconnect it.
Drop the gear box again.
Rotate shift-shaft in the gear unit until you find three clicks close together.The middle one is neutral,counter clockwise is reverse,and clockwise is forward.Pick a gear,say reverse,put control in reverse and slide her in.You'll need help to turn the flywheel,or remove spark plugs and you may manage it on your own.
To check what gear the unit is in,turn the prop,if it locks in one direction and ratchets the other direction,you are in forward,spins freely in both directions is neutral,locks both directions is reverse.
 
Sir thank you for you reply. However, it didn't work. I pulled the gear box out again. The prop is locked in 1 direction and ratchets in the other - so I presume as you indicated that means it's set in forward gear. I checked the throttle shift mechanism and verified it was set in forward direction. I also checked and found that the throttle shift mechanism does turn the spindle rod. I left the throttle shift in forward and then re-installed the gear box (which had been apparently set in forward gear). The gear box fit in fairly nicely, just a minor tweek on the prop and it slid up. tightening the bolts pulled it together very easily.

I then checked the throttle shift control and found that in forward, neutral and reverse the prop is still stuck in forward only.

Do you have any further advice?
 
Perhaps this is relevant. The shift-shaft pulls out of the gear box when the gear box is dropped. At that point, there's nothing to turn the gears.???
 
If the shift rod is pulled out of the lower unit you need to do some work.------removing the propshaft might be required.
 
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I was concerned about that. I had been trying to detach the shift rod from the shift link in the engine so that the gear box would be pulled out with the shift rod attached. Some earlier posts told me that the shift rod could be lifted out as the gear box was lowered because it's splined in. So I pulled it out. But now, on re-installation, the shift rod spline does not appear to be engaging the gear box receptacle.

It looks to me that there is a groove in the gear spline area that would hold a c-clip, possibly holding the spline into the gear box in the proper location. I don't see how it's possible to reconnect the shift-rod to the gear box unless the shift-rod is completely removed from the shift-link in the engine.
 
racerone is correct ,if you don't want to chance it yourself.If you decide to chance it,get a manual.The shift-shaft should separate from the rod,they are splined,they must have seized together.
 
Thank you gentlemen. I abandoned that engine, and bought an identical Merc 650 1 year newer, 1971. I'll use the old one for parts. This engine starts up well, runs for a 5 seconds, then shuts down. I'll start with lubricating the carburetor at the grease points? What's the best way to clean the carburetors? Just spray B12 cleaner into them? Are there any pins that need to be pulled out for cleaning? Is there any reason that I should attempt to remove the front cover to access the carburetors?
 
Re: 1970 Merc 650 - gear box removed - gear stuck in forward driver

Thanks Jeff. I dread the notion of switching carbs. Current plan is to thoroughly lubricate the existing carbs, and clean them with B12. On my previous Merc, a carb issue was resolved by lubrucating the grease fittings.
 
Yes, grease nipples or grease fittings are the site where grease gun injects grease. the grease appears to allow the carburetor fittings to slide easily.

Although that wasn't the problem in this case. The engine shut-off was apparently the result of old fuel lines and old fuel line fittings which were leaking mirco amounts and depressurizing the fuel system. I replaced lines and fittings, with a new filter, and the pressure held up. The engine ran consistently.
 
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