20' Sweetwater w/50hp Honda - what prop are you using?

[ahicks]

What I'm looking for, honestly, is somebody with the same or similar boat that's already tried a couple props? What were your results? What did you end up using?

Finally picked out a pontoon boat (private individual), and on the test drive I see I've joined the "it's only showing 4k on the tach" club? Engine seems to be running fine. I get the fact there are different pitch props available, and the difference in rpm's resulting from a pitch change (been boating many years).

This is a low time boat and I'm assuming it still has the original prop on it because the original owners never wanted to take the trouble to dial it in properly. I played with the trim and that really didn't produce anything meaningful until I went out too far with it, causing the rpm's to finally jump way up but obviously cavitating.

Boat will nearly always be lightly loaded, never pulling anything (thus the smallish engine).

I've spent hours searching through the prop forum and this forum which didn't really give me anything I'm willing to bet on. Have been on the Godfry/Sweetwater website looking for some insight on this boat/power combo for prop guidance, as well as Honda's site. All I see are lists of available props. No recommendations for a good starting point.

Thanks for any help/ideas!
-Al

 

[MinUph]

Re: 20' Sweetwater w/50hp Honda - what prop are you using?

Don't have the same boat and only a 40 hp honda. But it seems on my motor at least there is not a lot of choices for props.

 

[MH Hawker]

Re: 20' Sweetwater w/50hp Honda - what prop are you using?

The starting point is whats on it now.

 

[ahicks]

Re: 20' Sweetwater w/50hp Honda - what prop are you using?

With the Honda 50hp, going down through just the choices of 11" pitch props alone, I see 6 different diameter props ranging from 10 3/8" through 12". Dropping down to 10.5" pitch props, it gets easier as there are are only 2 diameters. Drop further, to a 10" pitch, and there are 3? These are all 3 bladed alum. props! Add choices available for 4 bade and stainless, and maybe the reason for my confusion/hesitation to 'just pick one' becomes clearer?

11" pitch props-
11” Pitch Honda Outboard Boat Propellers 50 HP 1995 & Newer BF 50/50A HP - iboats

1. There are obviously quite a few props to select from as I'm sure there are multiple diameters available for what appears to be a very comprehensive selection of available pitches? That's my problem. There's too many!

2. Yes, I could use what it's doing now to come up with a rough guess regarding pitch, but how to select diameter when choices vary from 10 3/8" to 12"? That seems like quite a range! Should I assume that as this is a pontoon boat I should go with one of the larger diameters, even though it's lightly loaded and will never be pushed into service pulling anything? I'm afraid that if I do that, I'm potentially throwing away speed to get torque I don't need?

The fact it's SO far off from what it should/could be doing is also a big factor for me. This would be MUCH easier if it were only a few hundred rpm off.

I realize eventually I'm going to have to make a "best guess". At this point I'm trying to collect as much info as possible to try and make that best guess as informed as possible. Comments from somebody with a similar boat and power combo would go a long way about now?

MinUph, do you know what size prop you're running? Comments regarding how that prop works?

Thanks guys, -Al

 

[steelespike]

Re: 20' Sweetwater w/50hp Honda - what prop are you using?

What is the gps speed at 4,000? What size prop? (near base of the blades or under the prop nut).
With the rpm,prop size and gps speed we may be able to tell if your numbers make sense.
It's not unusual for a tach not to be accurate.

 

[ahicks]

Re: 20' Sweetwater w/50hp Honda - what prop are you using?

What is the gps speed at 4,000? What size prop? (near base of the blades or under the prop nut).
With the rpm,prop size and gps speed we may be able to tell if your numbers make sense.
It's not unusual for a tach not to be accurate.

Bingo! Give that man an extra helping of ice cream! :joyous:

Took the GPS for a ride this afternoon. Just me, top down, 5mph breeze, max speed 19mph at 4000rpm indicated up wind and down wind, and it get's there fairly quickly. Those numbers didn't add up so I pulled the tach and checked its setting. Did some research and the setting was wrong! It was set for an older (6 pole) 50hp Honda. They changed them the year before this one was built. New ones are 4 pole - so the new setting will put the max rpm previously indicated to exactly where it should be (6000). This was all factory installed so who knows how many others are wrong as well?

First 4 stroke OB, so it doesn't sound like it's even close to turning rated rpm to me....

Thanks for pointing me in the right direction! -Al

BTW, for those following later, the prop is an alum. 12.1x9 3 blade