boat performance & prop changes

[lakegeorge]

Well I'll try to keep this short. Last year we bought a 2012 Berkshire 230cl triton with the Merc 150 4stroke motor. The 1st motor blew a 3 inch hole in the block as the dealer was testing it out before we ever got it.
Mercury rushed another motor and I had a problem with the throttle linkage coming out of the area where it's supposed to nest and it got fixed. the Merc service mgr flew to see about my performance and to try some different props ( 4 of them ) out and they all ran exactly the same,
33mph with 2 people on board @ 5,250 rpm's they also tried the motor at 3 different heights and no difference.

The motor is set with the anti cav. plate even with the bottom of boat, so I know that's good. The motor rpm's should run between 5,000 and 5,800 rpm's.
The props were all very different ( in pitch & dia. ) and yet no rpm changes, I know the old adage that if you change one way or the other it will affect your speed or rpm's, well on my boat it doesn't make a difference. The Merc. mgr. finally said to put the Enertia ss 3 blade prop on and that's what I have. This prop runs the same as the other 3.

I like the way the boat handles and my point is that you don't always get what you expect when changing props and a lot of times it's just a waste of money. Sorry for the long post.

 

[airshot]

Re: boat performance & prop changes

Something else is going on here, you can't change the pitch on a prop and maintain the same speed and engine rpm unless the change was so small that it was not detectable. With three different props I would assume that their would be at least an inch difference in pitch on each one. But then again if they added pitch but greatly reduced diameter it may not change enough to notice. Something or someone is pulling the wool over your eyes here, just doesn't add up to make sense. Is the tach functioning properly? I would have my suspicions..

Airshot

 

[lakegeorge]

Re: boat performance & prop changes

Something else is going on here, you can't change the pitch on a prop and maintain the same speed and engine rpm unless the change was so small that it was not detectable. With three different props I would assume that their would be at least an inch difference in pitch on each one. But then again if they added pitch but greatly reduced diameter it may not change enough to notice. Something or someone is pulling the wool over your eyes here, just doesn't add up to make sense. Is the tach functioning properly? I would have my suspicions..

Airshot

tach is working fine and 1 prop was a 15x15 4 blade ss

The Enertis that's on boat now is 151/8 x 14 and this is what Merc uses for most of their boat tests with the 150 motor.
I don't exactly remember the other 2 were I think 13.75 x ? and I think the other was 14 x 15 if memory serves me right. The dealer & Merc man was there for the testing and the results are as stated. I agree something is weird and no one knows what.
The main thing is that I can live with what I have but I would of liked to have gotten closer to the 5,800 rpm range just to see if the speed changed.
My wife can't take the wind at higher speeds so I only run it WOT for 1 minute just to make sure it's running correct. We usually cruise at around 19/20 mph.

 

[QC]

Re: boat performance & prop changes

Personally, I think this is more of a toon/hull limitation than prop stuff. Very odd not to have any difference, but 'toons are definitely different than say a bass boat when it comes to props.

 

[jestor68]

Re: boat performance & prop changes

Since you were testing props with only a 1 inch difference in pitch, what did you expect to happen?

And I bet each one was of a different "family". When you drop an inch of pitch and increase the diameter a little, plus use a prop from a different family, the results can be all over the place.

If you want your rpm up to the middle of the range, you need to change 2 inches of pitch; not just one.

As far as the first motor goes; that's what can happen when you take a green motor and run it at full throttle. You don't test props until after the break in period. You put one on there that historically is the correct one, with the understanding that it might require adjustment after the motor is broken in.

 

[jestor68]

Re: boat performance & prop changes

If you visit the Mercury web site and view some engine tests of the 150 4 stroke; you will see a 23 ft Manitou tri-toon doing 5700 rpm @ 34.2 mph using a Enertia 15-5/8 X 13 pitch prop.

At cruising speed(19-22 mph) it used 5 GPH.

In a Mercury SS prop, I personally lean toward the Mirage series for any pontoon boat for it's large diameter high thrust blade geometry.

A much less costly alternative would be a Solas New Saturn 15-5/8 X 13 ( similar blade design).

 

[lakegeorge]

Re: boat performance & prop changes

If you visit the Mercury web site and view some engine tests of the 150 4 stroke; you will see a 23 ft Manitou tri-toon doing 5700 rpm @ 34.2 mph using a Enertia 15-5/8 X 13 pitch prop.

At cruising speed(19-22 mph) it used 5 GPH.

In a Mercury SS prop, I personally lean toward the Mirage series for any pontoon boat for it's large diameter high thrust blade geometry.

A much less costly alternative would be a Solas New Saturn 15-5/8 X 13 ( similar blade design).

Thanks for responding. The first engine was not used for prop testing, it blew just as soon as the dealer gave it the gas. I have read all the prop tests that is on the Mercury web site before we tested any on my boat.
The prop that is on there now is what Mercury recommends, it is also used in many of their tests on their web site.
I will keep your recommendations if I decide to ever try any other props.