Really confused!

[BiXLL]

I have a SS Mercury Vengeance prop on a 2003 125 hp motor hooked up to a 22' pontoon boat. I just got this and have only had it out 3 times. I was convinced it had a spun hub as when I would try to tun it up to 4000 rpm it acted like it lost all its bite.

I took the prop off today to send it to a prop shop only to discover it has the plastic insert, not the pressed in rubber. The thing is, except for some small cracks at the corners of the plastic insert I can see no damage to it and see no evidence of anything spinning inside that should not be.

Is it possible for these inserts to go bad and not really show evidence of it?

 

[tpenfield]

Re: Really confused!

The prop may be cavitating due to a mis-match in the pitch versus the load.

 

[BiXLL]

Re: Really confused!

It is a 16 which from the research I have done is what my boat/motor calls for?

 

[joewithaboat]

Re: Really confused!

Make some marks across the hub to the prop, re-run it and see if the clocking position changes??
Was it used? If so it might have been worked/changed and not actually be as marked. Can only change so far but it could be a little different. If it is beat up it can cavitate, does it vibrate at all at other speeds when not cavitating?
Are you using a foil, heard of some props not working well with them.
Just guessing I'm no prop pro... or o/b for that matter..
Good luck!

 

[BiXLL]

Re: Really confused!

I will try the marking thing but it won't be till spring. I don't know if it was used or not, came with boat when I bought it. (used) I noticed no vibration at other speeds.

 

[joewithaboat]

Re: Really confused!

hydrofoil?

 

[BiXLL]

Re: Really confused!

hydrofoil?

no hydrofoil

 

[joewithaboat]

Re: Really confused!

You might get some advice from o/b people on raising or lowering your motor, after checking the prop. Like i said I'm not an o/b guy but if the prop is not at the proper height it will blow out or cavitate.
Good luck!

 

[ufm82]

Re: Really confused!

To answer your initial question, no. They cannot go bad without showing it. If it is broken it will be obvious. Since the hub insert isn't damaged it is obvious you have another problem. Motor too high, trimmed up too far, interference or something else introducing air into the prop. The prop is either cavitating ( spinning in the water after the water behind the blade boils) or ventilating (sucking air in from above and breaking the blades' grip on the water). Either way you need to adjust engine height or change prop pitch. Your engine will want to run well above 4,000 at WOT and you want to be able to achieve that.

 

[BiXLL]

Re: Really confused!

thanks joewithaboat for your time and efforts. I am also somewhat of a newbie to the boating world and am learning as I go.

 

[BiXLL]

Re: Really confused!

To answer your initial question, no. They cannot go bad without showing it. If it is broken it will be obvious. Since the hub insert isn't damaged it is obvious you have another problem. Motor too high, trimmed up too far, interference or something else introducing air into the prop. The prop is either cavitating ( spinning in the water after the water behind the blade boils) or ventilating (sucking air in from above and breaking the blades' grip on the water). Either way you need to adjust engine height or change prop pitch. Your engine will want to run well above 4,000 at WOT and you want to be able to achieve that.

Oh man, I am not sure there is any adjustment to drop this motor any lower? I am going to have to go and give it a better look. I am thinking this may be the problem though, as I have not been able to trim up much past midpoint on the trim gage without cavitating.

 

[steelespike]

Re: Really confused!

Typically on a pontoon the trim serves as an adjustment to reduce venting as much as boat atititude.I have seen similar pontoons of similar hp. that are running 13" props. Of course gear ratio may vary.What was the wot rpm and speed?Of course I've also seen some running a 17"
with the same motor.

 

[BiXLL]

Re: Really confused!

As I sit here and think back to the times I experianced the trouble, I am thinking the majority of passenger weight was 1/2 to 2/3 fwd of center. Perhaps I just need to keep a closer eye on where people sit.

 

[joewithaboat]

Re: Really confused!

Prob time for some pictures, in and out of the water.

 

[John_S]

Re: Really confused!

We need the gear ratio, wot speed, and rpms, but a Mercury Vengeance prop is more of a performance prop for planning hulls. Not something that would be typical of a pontoon. Also, props with rake and cupping can act like larger pitched standard props. Talk to a Bennington dealer about recommended props. Highly unlikely they put on the Vengeance.

 

[Thalasso]

Re: Really confused!

As I sit here and think back to the times I experianced the trouble, I am thinking the majority of passenger weight was 1/2 to 2/3 fwd of center. Perhaps I just need to keep a closer eye on where people sit.

Where do you boat? I am on the Beaver at Bridgewater

 

[BiXLL]

Re: Really confused!

Where do you boat? I am on the Beaver at Bridgewater

I am also on the Beaver. I used to belong to Nauticle Haven(last club on Rochester side) with my last boats, I just reserved a slip at River Harbour(last club on Brdgewater side) for next year.

 

[Thalasso]

Re: Really confused!

I am also on the Beaver. I used to belong to Nauticle Haven(last club on Rochester side) with my last boats, I just reserved a slip at River Harbour(last club on Brdgewater side) for next year.

Nauticle haven, is that where PITA was. You will like River Harbor.You know lilBuggy. He had a pontoon. He is at River Harbor

 

[BiXLL]

Re: Really confused!

Nauticle haven, is that where PITA was. You will like River Harbor.You know lilBuggy. He had a pontoon. He is at River Harbor

I don't know PITA or lilBuggy. I have been out of boating for about 5 years, last one before this pontoon was a Harris/Kyote deck boat. Captain Vinny used to run Nauticle Haven, he has retired and is bringing both his boats up to River Harbour also. Is that where you are?

 

[steelespike]

Re: Really confused!

I find that the gear ratio is 2.07:1 Pontoon wot speeds are all over the place but Guessing rpm at 5250,2.07 ratio,16" pitch and 20% slip speeds around 30 may be possible.
Pontoons usually have high slip numbers. A 4 blade prop is suggested for a pontoon as it may improve slip numbers and resist ventilation.