Possible Clutch Dog Issue?

[69Alumacraft]

I'm getting ready to go pull the L/U on my 1969 Mercury 1000 (100HP) to check the clutch dog.

Back in May of this year I took my step son's boat out on a test run to see if we had fixed an issue we had with fuel starving. I ran the boat up to near full speed (didn't want to go full speed since this was the first time we have had it on the water and it was pretty choppy) and all seemed to be going well until I turned back toward the dock and backed off the throttle a little bit to make the turn. When I put the power back down the engine just revved without any thrust! My initial thought was that we spun to prop off but we were able to make it back to the dock and low speed and when I put it in to reverse to stop at the dock it definitely still had the prop.

My step-son checked around and someone suggested that the clutch dog was worn so a buddy of mine and I are going to pull the lower unit today and I would like to know what I should be looking for to see what needs to be fixed/replaced.

Any other words of advice would be appreciated.

 

[HopinImFloatin]

Re: Possible Clutch Dog Issue?

im no expert but it still seems that it could be a spun prop, may only spin under heavy load. i would mark the hub , run it hard and see if the marks still line up after you experience the slip, easier than tearing things apart to check. just my opinion

 

[lncoop]

Re: Possible Clutch Dog Issue?

+1. Symptoms could indicate spun hub. Let's hope they do.

 

[Texasmark]

Re: Possible Clutch Dog Issue?

What I would do: Put a 2x4 between the prop and anti vent plate with the gear selector in F. Get on the flywheel nut with a torque wrench and put about 50-60 ft-lbs of torque on the nut in a CW direction. If the clutch dog is ok, it will take it and not do anything. If the prop is ok, it will do nothing. If either is bad, you will get some movement then just mark your prop and do it again, checking to see if your marks from the brass insert to the outer prop shell have become mis aligned.

On Reverse, slowly rotate the prop slowly while shifting to R so as to not damage the linkage.....R has keys and slots and has to match for it to engage...unline F gear.

Repeat the process now but going CCW and that will check the R part of the clutch dog.

Others surely have their idea, but I could do this test with minimum tools and 50-60 ft-lbs isn't all that much. The prop nut torque is 55 and the flywheel nut torque is 120 ft-lbs so you won't be loosening it up with this test nor tearing anything up.

Mark

 

[69Alumacraft]

Re: Possible Clutch Dog Issue?

If either is bad, you will get some movement then just mark your prop and do it again, checking to see if your marks from the brass insert to the outer prop shell have become mis aligned.

Mark

Mark,
I finally got tired of the boat just sitting there and this weekend was the first chance I've had to tear into and have the chance to get to LA for parts (if necessary).

I tried what you said and made a mark on one of the tabs on the lock washer on the driveshaft and a matching mark on the prop. I noticed that when I turned the flywheel in forward (while blocking the prop with a 2x4), the mark on the tab moved about 1/4" in relation to the mark on the prop but when I let off the pressure on the flywheel, they went back to almost matching up, though it was still skewed clockwise to the mark.

I was curious about how much movement is too much?

 

[Texasmark]

Re: Possible Clutch Dog Issue?

You found your problem. When you amplify the force you applied via the engine HP, it probably keeps turning and doesn't return.

Mark

 

[69Alumacraft]

Re: Possible Clutch Dog Issue?

Mark,
Thanks for the reply after so long.

I guess I'm not sure if the problem is the clutch dog or the prop.