Little/No Prop Thrust at High Torque Merc MR-1

[four winns 214]

Boat: 1984 Sea Ray cuddy
Engine: Merc 228R
Drive: Merc MR-1
Both original to boat

Went out for a dinner cruise tonight. Like it has for the last 10 years, it throttled up and planed right off. About five minutes later, the engine rpm revved and the prop lost almost all thrust. After throttling back, things seemed fine. We slow cruised back to the marina at 2000 rpm. No overheating or other issues. Outside marina entrance, I throttled back up and prop lost thrust again.

Where do I start trouble shooting?

 

[Bt Doctur]

THe rubber prop hub comes to mind

 

[Scott Danforth]

coupler comes to mind as well

 

[bobkat1864]

Hi there...make a mark with waterproof marker across the center of your prop hub, then go for a short ride. After that, see if the marks no longer line up.

 

[four winns 214]

I'm fairly certain the issue was the prop hub. There wasn't evidence of a coupler problem.

I've never spun a prop hub and haven't ever seen one, but there were light scrub marks on the circumference of the hub and the inside of the prop to which the hub mates. I'll know on Sunday when I water test it if a new hub fixed the problem.

A related question: When I removed the prop today, the prop nut didn't seem to be torqued to the 55 ft. lbs specified by Merc. The tab washer was in place and not deformed so I don't think the nut moved. Could this have any correlation to a spun hub? I'll have a talk with the knucklehead who installed the prop without properly torquing the nut (me).

 

[achris]

A related question: When I removed the prop today, the prop nut didn't seem to be torqued to the 55 ft. lbs specified by Merc. The tab washer was in place and not deformed so I don't think the nut moved. Could this have any correlation to a spun hub? I'll have a talk with the knucklehead who installed the prop without properly torquing the nut (me).

No.

 

[four winns 214]

To close this out-- it was the prop hub. A new hub took me 80 miles cruising around Kentucky Lake and Lake Barkley on Sunday and Monday with no problems.

 

[achris]

To close this out-- it was the prop hub. A new hub took me 80 miles cruising around Kentucky Lake and Lake Barkley on Sunday and Monday with no problems.

Nice to hear it was an easy fix.

I'm curious on your weekend cruise. 80 miles. Any idea how much fuel you burnt? Trip like that would have cost me about over a hundred dollars. And I'm only running a V6.

Chris....

 

[four winns 214]

Nice to hear it was an easy fix.

I'm curious on your weekend cruise. 80 miles. Any idea how much fuel you burnt? Trip like that would have cost me about over a hundred dollars. And I'm only running a V6.

Chris....

I used around 25 gallons. I won't know for sure until I fill up. i don't have a fuel flow meter. I usually get about 3-3.5 statue miles per gallon at a cruise of 20-25 mph.