Motor revs whilie towing a tube, with out incresing speed.

[crownholder]

I was at the lake Saturday, for the first time with a new(new to me) boat. A couple of times while running up the lake, the motor would let out a quick rev, and i would pull back on the throttle and start over. Then later in the day i was pulling someone on a tube and it did the same thing, so i throttled down and then tried to punch it again and the reved up and was going, just not as fast as it should have been. I am thinking that the hub is slipping, but not sure. the boat is a 95 crownline, 5.0L(235hp) has a new 17p SS prop from Cabelas, old owner put it on. Had 3 people in boat and one on tube. After that we quit tubing, had everyone in boat and i punched it and took right off with out any slipping or reving? Is it the hub, the prop, the pitch, lower unit?? Help please.

 

[spdracr39]

Re: Motor revs whilie towing a tube, with out incresing speed.

what rpms are you running at wot with that prop ? And what type of hub kit does it have?

 

[ufm82]

Re: Motor revs whilie towing a tube, with out incresing speed.

It's slipping but I doubt it's the hub since it's "new". It sounds more like the prop is cavitating- losing its bite in the water and spinning free in the water. It's especially obvious when pulling tubes with a lot of horsepower. While it "could" be a hub issue, I'd be looking at that, especially since the boat is new to you. Where is your trim? Does it break loose going straight or in turns? How does it do at take-off? What size/hp boat did you have before if any?
You can check for a hub issue by marking the hub and the barrel of the prop and duplicating the issue. If the marks no longer line up when inspected the hub has slipped. New hubs don't usually slip but anything is possible. But it sounds more like a cavitation issue to me. May want to drop to a lower pitch prop when pulling tubes...

 

[steelespike]

Re: Motor revs whilie towing a tube, with out incresing speed.

have you tried trimming down slightly or moving one or 2 people to the back seat.
sometimes there is no need nor is it necessarily right to run with full trim.
I would expect to trim down for some water sports and sporty turns.
Is there a transducer or anything in the bottom or the transom that might disturb the water around the prop?
Is the bottom clean and smooth and the prop clean?

 

[crownholder]

Re: Motor revs whilie towing a tube, with out incresing speed.

I am taking the boat out again this weekend, so i will have answers to all of your questions, which will then solve my problem. Thanks for the information. will be back with better info on the boat.

 

[crownholder]

Re: Motor revs whilie towing a tube, with out incresing speed.

One other thing, could the hydrofoil cause cavatation? An answer to one of the questions, is yes there is a transducer that could affect the water.