What could be causing the high rpms?

[TRValeri]

I have a Four Winns H190 with a Volvo-Penta GXI 5.0 with sx outdrive. I just put a new 17 pitch prop on to take my boat to a lake at 5000 feet. On Mothers Day I took a big load of 7 people at about 1200 pounds for a little cruise. Needless to say it was hard to get that load on plane. On the way back to the dock I wasn't able to get above 10mph and certainly couldn't get on plane. Whenever I gave it more throttle the engine would rev to high rpms. The boat reminded me of a car with a bad clutch. Fearing I spun my prop hub, I took my new prop back to the shop and the mechanic said I definatelt didn't spin the hub, but he gave me a new prop to be safe. I haven't put the boat back in the water, but I was wondering if any of you with more knowledge than me could give me an idea of the possible problem. Ill put the boat back in the water this weekend, but don't want to cause any damage.

Thanks for your response.

 

[Don S]

Re: What could be causing the high rpms?

A spun couple could do the same thing, but you would normally have noticed a burned rubber smell
Another possibility is a slipping cone clutch in the drive. Perhaps the cable is not pushing the shift mechanism all the way into gear, or water in the drive.

 

[BreakOutAnotherThousand]

Re: What could be causing the high rpms?

What was the pitch and diameter of your factory supplied prop?

What is the diameter of the 17P you bought?

You have a 19ft boat with a 270HP motor, depending on the SX gearing, you would be pushing a 23, if not a 21 stock.

My 20ft with a 280hp is pushing a LaserII 23P SS, when loaded at Lake Tahoe, I use a Laser II 21P SS.

Im thinking you propped too low, and the diameter is too small??

 

[Don S]

Re: What could be causing the high rpms?

Im thinking you propped too low, and the diameter is too small??

It was running fine most of the day, then the rpms went up and the speed went way down. I doubt anyone got out and changed the prop to suddenly slow it down.

 

[Bondo]

Re: What could be causing the high rpms?

It was running fine most of the day, then the rpms went up and the speed went way down. I doubt anyone got out and changed the prop to suddenly slow it down.

Ayuh,... But crusin' through a patch of weeds,... Could do that....

 

[Don S]

Re: What could be causing the high rpms?

Read my reply in context to what I replied to.
The OP also took the prop off and never mentioned anything about weeds balled up on the prop. I would think he would have mentioned that.

 

[TRValeri]

Re: What could be causing the high rpms?

What was the pitch and diameter of your factory supplied prop?

What is the diameter of the 17P you bought?

You have a 19ft boat with a 270HP motor, depending on the SX gearing, you would be pushing a 23, if not a 21 stock.

My 20ft with a 280hp is pushing a LaserII 23P SS, when loaded at Lake Tahoe, I use a Laser II 21P SS.

Im thinking you propped too low, and the diameter is too small??

I'm not sure on the diameter of the 17p, but it is a Volvo-Penta brand. I went down to a 17p at the recomendation of my Four Winns dealer. I usually run the boat pretty heavy with 6-7 people and an ice chest. At sea level I was only pulling about 4300RPM with my stock 21p prop. The drop in pitch was to compensate for the normal overload I carry as well as a relocation of the boat for the summer to Shaver Lake at 5000ish feet.

I look the prop back to the dealer who said the hub had not been spun, but he gave me a new one anyway. I'm going to put the boat back on the lake this weekend and hope the probelm has gone away... I'm not holding my breath on that. If the problem persists then I guess I'll have to do the drive of shame back to the valley with my boat in tow.