Prop Damage

[maxumized]

Anyone think this prop (images attached) is damaged enough to keep a 1997 Maxum 1750 at 3500rpm instead of 4400-4800 rpm at wide open throttle?

I've been through and through the wide open throttle checklist and still can't get more than about 3500rpm.

It is a 14.5 x 19 whereas the OEM prop was a 13.75x21. That being said, shouldn't this new one actually be over revving the boat?

This just doesn't seem like bad enough damage to lose over 1000 rpm, but I'm no expert.

 

[stimps]

Re: Prop Damage

Looks like scrap to me. It does not take much to make a large change. The damage to that prop is extreme and I would have thought it could cause the issue you have. It is also "listed" as a larger diameter than what you previously ran. I say listed as it looks like it's probably now about the same size. Time for a change.

 

[45Auto]

Re: Prop Damage

That prop's definitely in line to become an emergency-only spare, but I don't see how it could cost you 1000 RPM. A beat up prop will usually cavitate and let the motor rev HIGHER while the boat goes slower. Hard to see how beating up the prop would make it slip less.

My neighbor has been running a prop that's at least as bad behind his 18', 3.0L Chaparral for almost 4 years now. Makes no difference at all to the boat's performance.

 

[steelespike]

Re: Prop Damage

I assume the rpm has resulted in a decrease in speed as well?
I'd have the prop repaired and check the results you shouldn't run it like that anyway.It will cause premature wear of the bearings and seals in the gearcase.
Definately a bigger repair than a prop.

 

[maxumized]

Re: Prop Damage

Yeah, I may just go ahead and get a factory size prop. Anyone think it'd be worth going stainless on a 3.0?

I've about had it with this boat anyway... been fighting the 3500rpm limit for over a year now. I'm on a brand new motor, rebuilt carb, fuel pump, ignition, and I've been completely through the fuel system from the tank pick up to the carb. Vacuum and pressure tests pass fine.

I'm starting to wonder if the outdrive is somehow bogging the motor so bad it can't pull past 3500. It's the only part I haven't replaced on the darn thing.

Who knows.

 

[steelespike]

Re: Prop Damage

Problem when going to ss from al results are unpredictable. improvement could be from a few tenths to a few mph.I would stick with aluminum. How is your hole shot?Have you checked and confirmed the gear ratio?Have you tried a little gas sprayed directly into the carb at speed?Confirmed timing advance is correct? Tried manipulating the timing at speed?Are you sure all cylinders are contributing at apeed. Maybe valve float broken spring?What is the speed at 3,500?If you want to improve the hole shot the Solas Amita 4 blade has proved itself over and over.With your rpm struggles I would go to an 18" pitch.

 

[milmat1]

Re: Prop Damage

If you choose a SS Prop rather than AL. Do you stand a better chance of damage to the lower unit since the SS wont flex like the aluminum did. I'm thinking the prop may not be damaged as easy but something has to take the hit...??

 

[tschmidty]

Re: Prop Damage

Not worth it to go SS, but to second others, the prop is not causing the RPM problem, although that thing should definitely be replaced.