Cruising then instant speed loss and rpm rise

[synergy141]

Hi, I was out tonight and I was cruising along at about 3700 rpm (1998 Mercrusier 5.0) then all of a sudden I lose speed and the rpm's go over 4000. I cut the throttle and slowed down. Low speed operation was normal. Waited 20 seconds and hit the throttle, the boat was trying to get on the plane but the rpm's would again rise without power. I then cruised back to the dock at 1500 rpm raised the leg and checked everything out and it seemed normal. There were no weird noises or smells. I sat there for about 20 min, restarted and I puttered along at 1500 rpm for 15 min, Hit the throttle and it was fine, acting like normal. It almost felt like prop slippage but its fine now so I don't really know what went on.

 

[Bt Doctur]

Re: Cruising then instant speed loss and rpm rise

slipping prop hub most likely

 

[cr2k]

Re: Cruising then instant speed loss and rpm rise

I would go with prop slippage. Clean and paint a line across the nut and the hub of the prop to the outer part of the hub. Next time it happens check prop, if lines not matched prop hub. Or just change your prop and see if it never happens again. Any good boat shop could look at your pro and tell if the hub is bad.

The rubber hub could have gotten so hot it re bonded when you let it sit and cool. Better then the alternative the Drive coupler. $300 part and engine pull.