slipping, lost power, RPMs up

[ryansdata]

first post.

2006 Crownline 180 BR 4.3 Merc with alpha drive (not sure 1st or 2nd gen, don't know prop pitch). 48 hours.

Bought used last fall. winterized and summerized by professionals.

Ran great all day Saturday; on the way back to dry dock, it planed as normal, and after a few minutes at about 3500 RPM, I lost power and the RPMs increased. This was repeated and the same result. Temp and oil pressure remained normal. Played with Trim, no difference.

I limped back at 2500 RPM and 10 MPH.

I noticed a course spray, almost a wide, low rooster tail at the stern.

The mechanic has it, just waiting for his diagnosis.

I searched and found a couple of things and was hoping for some input from you-all. Any other ideas?

1. a worn clutch and gear dog
2. lower shift cable malfunction
3. slipped prop hub.

I am not mechanically oriented to repair myself (and the boat is 1.5 hr away), but I would like to sound informed when the mechanic calls.

Thanks

data

 

[45Auto]

Re: slipping, lost power, RPMs up

A dog-clutch (Alpha outdrive) won't slip. It's not like a clutch on a car. It works by engaging square cuts on the faces of the gears with each other. It's either in gear or not.

Same with the shift cable, it'll either work or not. Either it pulls the dog-clutches close enough to engage or it doesn't. No half-way engagment is possible.

Your #1 and #2 are pretty much impossible from the info you gave. It's most likely #3. About the only other think that could possibly slip in a boat is the splined coupler on the engine, but they usually strip all the way out when they go.

 

[ryansdata]

Re: slipping, lost power, RPMs up

thanks for the reply.
no word yet from the marina.
somebody today posted about running aground and possibly a loose hub. i did not hit ground, but i do recall sneaking thru 2.5 ft water, slowly, and there were many small floating debris (large sticks, small logs) which I don't recall striking but others were driving, too.
Perhaps it was from that.
overall, the hub sounds more benign than the others, correct?

 

[Oldskool]

Re: slipping, lost power, RPMs up

Depending upon the brand of prop, yes, it should be a relatively inexpensive fix if it is a prop hub issue. You may be able to simply replace the hub unit, such as on some Michigan Wheel units. Worst case, new prop.

 

[45Auto]

Re: slipping, lost power, RPMs up

Doesn't take running aground to make a prop hub slip. Only one I've ever had slip just let go on the river one day when when taking off. Clear deep water, nothing to hit. I thought the boat had popped out of gear at first. Boat would do just like yours, would barely move at low RPMs. Higher RPM just causes the exhaust to blow a roostertail of water without moving the boat. Put on my spare prop (hopefully you carry a spare prop) and kept going.

Cost $40 to have a new hub put in the prop that was slipping.

 

[ryansdata]

Re: slipping, lost power, RPMs up

update:
mechanic called, slipped prop hub. will go up next weekend to check it out thanks to all

 

[ryansdata]

Re: slipping, lost power, RPMs up

update on the update: just got back from the lake. a second mechanic actually took it for a test drive and couldn't replicate anything.
Good news: nothing was broken, worked well all day
Not sure what the cause - perhaps some debris maybe that fell off when it was dry docked.