Mercury 60HP 2 Stroke

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Oct 23, 2016
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Help! I am just doing trials on my new to me RIB. It has a 1999 60HP Mercury Autolube 2 stroke. I swapped over to a Stainless Prop as one of my first jobs. On my second run yesterday it was intermittently dropping out of gear. After an hour I lost drive in forwards and reverse. Checked linkages which were fine. Interestingly prop turns slowly in neatral and still does. That suggests a bottom end problem to me right? My next step is to remove the gearbox. Could this be anything to do with the prop replacement? I have a service manual and a 20 ton press. Is this something a reasonable diy mechanic can look at or should I be looking for a replacement gearbox. Any advice appreciated thanks.
 

GA_Boater

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In neutral with the motor idling, the prop will lazily turn. It's interaction with the gears and thick lube and normal.

Have you swapped back to the original prop to eliminate the lower unit? The SS prop may have a spun hub.
 
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The original prop is away being repaired at the moment. The first thing I looked at when it failed was the nut on the spline. I figured that it would still be turning if it was a prop problem but it was not moving apart from the creep. Am I right to assume that the creep originates from the engine shaft or is it because of the exhaust? If it comes down the shaft then am I right to start at the gearbox? Thanks
 

GA_Boater

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Forgot to give you a :welcome:

The creep is from the oil and spinning gears, exhaust has nothing to do with it. Neutral creep on muffs is not a problem, it is absolutely normal.

Draw a line across the hub and prop and try the boat in the water. You can even back it down the ramp with the boat tied down to the trailer and and use forward and reverse a few times. Check the line across the hub and if it isn't still aligned, the hub is slipping. It's an easy test and you can avoid looking for lower unit parts or a repair.
3-blade-prop1.JPG
 
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Oct 23, 2016
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I will give that a go thanks. If the nut in the centre is not moving when in gear does that not rule this out? I am using a Apollo XHS SS prop so no rubber bushing. It has a plastic insert which in theory is very obvious after a break. I attach a photo.
 
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Mine is actually an Apollo XHS but I think it works in the same way.
 

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GA_Boater

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Have you taken the prop off to examine the plastic hub?

I want to exhaust all the possibles before advising getting or repairing the lower unit.
 
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