need advice on a new prop

[reel mccoy]

Guys need you help for a new prop. I have a DF115 Susuki outboard. It is hung on a 2110 Nauticbay boat 2008 yr model for both. Currently I have a Solas 13.75 X 19 4 blade prop (Dealer installed) on it. I am still in the brerakin period on the motor. I was unable to hold plane at 3000rpms and could hold at 4000. The specs say 5000 to 6000rpm's at WOT. I can over rev my motor easily. top speed is around 35 not to sure on that was watching rpm's not speed. The bay boat weighs in around 1550 LBs. I had only 2 men in the boat when I was doing the breaking runs.

My question is I want a SS prop but think I need more pitch and is a 3 blade ok for a 4 stroke, any Ideas?

 

[steelespike]

Re: need advice on a new prop

While I'm not an expert from the few boats I checked in your range including a Nautic bay 2200 with a 200 hp Yamaha.Your specs don't seem to add up.
the 200 was running a 19 in. on the 2200.Other 115 hp on boats of similar size and weight to yours were running 17in. props almost without exception.
A four blade would change things a little but should give better low end performance with a slight sacrifice of top rpm.
I'm a guy a little short on prop info it seems you would normally be running a 3 blade in the 17in. range.You might double check your prop size and your tach accuracy.In my mind you should be over propped at 19in.Have difficulty making max rpm.Maybe I'm missing something.
A stainless is generally more efficient than an aluminum.
The experts should be along with more specific info.

 

[Frank Acampora]

Re: need advice on a new prop

Agree with Steelspike. You are asking a lot from ANY 115 horsepower engine on a boat that size. I would be surprised if you could over rev the engine--especially since it is a 4 cycle. Finish your break-in period then take a few wide-open throttle runs to establish top speed and RPM. Then if RPM is above recommended Manufacturer range take the boat back to the dealer to have the tachometer accuracy checked under warranty.

 

[reel mccoy]

Re: need advice on a new prop

Like that warranty Idea, think that is the road to go, thanks for the info.
Oh and hope I am not seriously under horse power would hate to have to buy a new motor already not!

 

[walleyehed]

Re: need advice on a new prop

I use a DF115 of one of my prop test boats, and due to the gear ratio of that engine it swings about 1 size higher than would be expected.
That engine also has a rev-limiter not too far above 6000....."maybe" 6400 if I remember right.
Are you at the 6400rpm mark?
I just done some calculations on this and I believe there is something off with either prop size or Tachometer...at 19P in 4bld, figure 19.8P in that prop style at 35mph (speedo, gps?), 2.59:1 ratio, the RPM would be about 5500 with a realistic 12% slip ratio figured in.
I would say the tach is either bad, or possibly on the wrong setting, the speed is "WAY" off, or the prop pitch is not as stamped.
I have a feeling it's the prop or the tach and would lean in the direction of the tach.
Can you verify P/N on prop for me?
How are you measuring speed? paddle wheel, gps, etc..?
We'll get it figured out!

 

[reel mccoy]

Re: need advice on a new prop

walleyehed

I am leaving for PA 19 feb till middle of next month. At that time I will have the boat in the water and document everything you have asked for. I went and looked at the prop to see the part number all that is stamped on it is SOLAS 13.75X19 no other numbers on outside of prop. could it be stamped on the inside of prop? can't see it from frony of exhaust port. used a speedo for the milage but will have GPS when I return.