New toon is pretty slow. Help with prop selection?

[dubya1982]

Hey guys I'm hoping you all can help me out.

I'm a brand new boater. After about a month of shopping we finally bought a new pontoon. We decided to go with the 115 HP motor over the 90 HP because we wanted more speed so we could do some tubing and maybe a little skiing.

We ended up with a 22ft Bentley 220 SE with 115hp Mercury and 2 - 25" toons. No strakes and no under skinning. We dropped it in the water on the way home from the dealership and I was very disappointed with the results. The water was pretty calm, wind was calm, only 2 adults and a baby on board and we couldn't get more than 22mph. I thought for sure we'd get more than that, but that was the most she would go. We were topping out at around 6500 rpm.

After some research I'm discovering the problem could be with the prop. The boat came with a Quicksilver aluminum 3 blade prop. It is a 14x10RH with a 10 pitch.

What do you guys suggest? Do you think the prop could be the problem? From what I've read online this boat should be able to do upper 20's to 30mph.

 

[jestor68]

Re: New toon is pretty slow. Help with prop selection?

What Mercury motor did you buy? The 4 stroke or Optimax?

They have completely different rpm ranges for prop selection. But there is no doubt that you could use more pitch; how much more depends on which motor you have.

The Mercury web site has tests of both types on Bentley pontoon boats. Viewing them will give you an idea of how certain pitches might do on your boat. Hint; the Black Max Extra cup 11 pitch seemed to be the best compromise for the 4 stroke 115(30 mph), while the 15 pitch worked well on the Optimax(29 mph).

 

[dubya1982]

Re: New toon is pretty slow. Help with prop selection?

What Mercury motor did you buy? The 4 stroke or Optimax?

They have completely different rpm ranges for prop selection. But there is no doubt that you could use more pitch; how much more depends on which motor you have.

The Mercury web site has tests of both types on Bentley pontoon boats. Viewing them will give you an idea of how certain pitches might do on your boat. Hint; the Black Max Extra cup 11 pitch seemed to be the best compromise for the 4 stroke 115(30 mph), while the 15 pitch worked well on the Optimax(29 mph).

I have the 4-stroke.

I did see those tests online after I posted this but they were for a little larger boat. The tests were done on a 24 footer and I have a 22 footer. I'm not sure how much of a difference that would make. Do you think results will be about the same?

 

[Bamaman1]

Re: New toon is pretty slow. Help with prop selection?

The rpms speak, and you need a little more pitch on your prop to lower you to about 6000 rpms. Twin toon 115 hp 4 stroke boats normally max out about 25 mph. The Optimax 2 strokes will usually be 2 mph faster, and pull a little stronger.

The best way to get to 30 mph is lifting strakes on a 2 toon boat, which gets your nosecones out of the water.

I have seen the Bentley tritoons with strakes perform very well with 115 hp. You really should have taken an in water demo before purchasing your boat. See what your selling dealer is willing to do to please you.

 

[jestor68]

Re: New toon is pretty slow. Help with prop selection?

I have the 4-stroke.

I did see those tests online after I posted this but they were for a little larger boat. The tests were done on a 24 footer and I have a 22 footer. I'm not sure how much of a difference that would make. Do you think results will be about the same?

Look again. The 4 stroke 115 test I referred to was on a Bentley 220 Fish. 30 mph @ 6200 rpm with the BM extra cup 11". The extra cup 11" would act like a 12-13 pitch. The extra cupping adds effect pitch to the prop.

While your result might vary slightly, it should be close.

The difference in weight between a Bentley 22 and 24 is 200 pounds(according to the web site).