exhaust causing prop ventilation problems?

[Brian8mm]

I have a Regal 2100LSR with the 5.0 GXI. When I run the engine on earmuffs all the cooling water and exhaust gases drain out just past the transom, none come through the hub (trim is up). Doesn't seem right to me but other, older boat owners have told me it is normal and not a problem so I have not tried to fix it.

Today I was running max loads (1300 lbs plus pulling a tube at 2500') and even on a straight takeoff I noticed the engine reving (4000 rpm) while only doing 20 mph whenever i punched it. After a couple second the prop would grab and I'd excelerate to 30 mph and throtle back (cruising is about 3300 rpm for 30 mph with this 4 blade 18" aluminum prop). Trim is all the way down.

I was wondering if the prop could be pulling the exhaust gas down and allowing the over reving?

I'm only a couple years into boating and other than a spun hub last year have not had any problems.

Anu advice is appreciated.

Brian

 

[WizeOne]

Re: exhaust causing prop ventilation problems?

I think you have another spun hub. Mark the back of it with a paint pen and I am sure you will see the hub has slipped.

 

[Don S]

Re: exhaust causing prop ventilation problems?

I doubt you have a spun hub on the prop, or coupler, or you wouldn't see speeds of more than 1 or 2 mph and it still pulls. Let alone 20.
If the exhaust bellows is in place and not broken, then excess air to the prop from the exhaust isn't the problem, and the water not coming out of the exhaust is also not a problem.
Sounds a lot like you have a prop size/pitch/cup/who knows problem.
Will move this over to the prop forum. Might want to post your WOT rpm that you have now and what prop you are using.