New to pontoons, prop question

[TheFatKid]

Hey all,

I recently purchased my first pontoon boat. So far the family and I love it however I'm a little bit disappointed in the performance. I was never expecting a ton of speed but I did expect the engine to perform according to manufacturers specification. It have a SS190 Lowe with a Merc 60 on it. The data on the engine claims 5500 - 6000 RPM @ WoT. I'm seeing 4800 RPM max with me, one passenger and relative smooth waters. I tried playing with the trim to find the sweet spot so I'm out of options there.

My research is telling me that I will likely need to consider a prop change to get the engine into the correct RPM range. Do any of you have any thoughts on this? The prop I have has a stamped number that ends in 11P so I'm assuming the factor prop is an 11 pitch.

Upon finding this site I did a bit of searching and it seemed to corroborate my other research.

I want to have a spare prop anyway, so one will be purchased no matter what.

Thoughts?

Thanks,
Adam

[DWRAT]

Is your Merc 60 a Bigfoot???
If so this would be a good choice. http://www.amazon.com/Mercury-Spitfire- ... M+Spitfire

[TheFatKid]

It's a Command Thrust. I think, based on conversations with people, that the CT is the newer version of the Big Foot?

[BobG]

If you're only hitting 4800 RPM @ WOT with an 11" pitch prop, you'll need to drop down at least to a 9" to get where you want to be. Props usually come in 2" increments. The pitch of a prop, is how many inches it moves forward, in one revolution, with no slip.

[TheFatKid]

Thanks, would I be safe assuming that anything that fits the Big Foot will fit my Command Thrust?

[BobG]

would I be safe assuming that anything that fits the Big Foot will fit my Command Thrust?

Seeing as how those are just different names for the same thing, I would guess "yes".

[Strake]

Adam,

If the boat and engine were purchase NEW, I would suggest going back to the dealer and having them re prop it with a smaller pitch as suggested above. They should be responsive to get it in the manufacturers WOT RPM range.

If you bought the boat and engine used, then you'll need to re prop at your expense. Either way, I would get it changed. If it's on your dime, keep the current prop as a spare for emergency use should you tear up the new one.

[rancherlee]

What kind of speed are you seeing with the current prop? Since you said you only are hitting 4800rpm that puts you at around 16-18mph which seems a bit slow for a 11p prop @ 4800rpm on that motor/pontoon combo. You might have a setup issue where the throttle cable isn't adjusted properly OR the tachometer isn't reading correctly. The next prop down is a 9 pitch which would bump your RPM's up to ~5800 at the same speed but I think that's too small for a 60hp engine with a big gear ratio lower unit.

[TheFatKid]

What kind of speed are you seeing with the current prop? Since you said you only are hitting 4800rpm that puts you at around 16-18mph which seems a bit slow for a 11p prop @ 4800rpm on that motor/pontoon combo. You might have a setup issue where the throttle cable isn't adjusted properly OR the tachometer isn't reading correctly. The next prop down is a 9 pitch which would bump your RPM's up to ~5800 at the same speed but I think that's too small for a 60hp engine with a big gear ratio lower unit.

You hit it perfectly, 18mph. GPS measured. I was considering a set up problem, nothing I have the skill set to look at myself. I have a friend who is a professional boat mechanic. He's busy but he's going to try to get a look at it this week.

[crookedlaker]

sounds like the engine may be mounted too low
may try to move up a hole and see if that helps, shouldn't be too difficult with a 60 hp
That 11 pitch prop sounds like the correct prop for a 60

mike