2008 Suntracker 18' Bass Buggy prop choice

[ddh1961]

Hello everyone, got a prop question on my 18' Bass Buggy pontoon. Current engine is a 9.9 Merc 4-stroke (was a HP-restricted residential lake boat) and I have a 2015 60hp Merc Command Thrust (Bigfoot) 4-stroke on order as it's now seeing open water use. Looking for top speed as I fish with guys on bay boats doing 25-30 mph cruise speed. Boat is about 1300 lbs empty, with about 500 lbs people & gear with 30 gal fuel. Looking at a Spitfire 4-blade prop and Merc's prop selector recommends a 13.8x13 Spitfire prop. Dealer sold me a 12.5x19 Spitfire (not mounted yet as engine has not arrived) but this seems a bit extreme for a 60hp engine, even with a 2.33 drive, to reach the 5500-6000 rpm spec. Looked at a new 18' Bass Buggy at the dealership the other day & IIRC it had a Black Max 3-blade 14x11 prop on its 60hp CT. I'm reading like crazy trying to get schooled up on this, but could use some advice- anyone think the Merc calculator recommendation of 13.8x13 is better than my dealer's recommendation of 12.5x19 for the 4-blade Spitfire on this boat? Thanks for any help, and if I need to provide additional info please let me know.
Thanks,
Dave

 

[jestor68]

Something in the 11-13 pitch range sounds about right. Tracker "estimates" speed range of 18-23 mph with the 60 hp on the 18 ft bass buggy.

The dealer should let you test a couple different props to get the right one. The 19 pitch sounds like way too much.

 

[ddh1961]

Thanks for the info, Jestor. I decided to go with Merc's prop selector & your advice & just ordered a 13.8x13 Spitfire online. Will return the unused 12.5x19 to BPS tomorrow & will be saving 40 bucks on the cost of the new prop! Thanks again.
Dave

 

[steelespike]

Let us know your results.As you probably realize it takes a lot of hp to make a pontoon fast.
Merc high thrust performance report for a B.B 18, actually a 20', at about 1375 lbs.dry weight
wot speed with a 9" prop was 17.2 mph @ 5930.
My limited research indicates the longer pontoons (over 20 ft) tend to be faster even though
about 700 lbs heavier. For a 24/26'.24ft deck 26' tubes. Speed with a 60 high thrust with a 11" prop was 20.5 @ 5700 rpm.
These are both with a BM prop. I feel that the Spitfire may do a little better if the 13" pitch isn't too much.

 

[ddh1961]

Steelspike- got the boat back from the dealer this past Saturday with the new engine installed but haven't been able to get out on the water yet. I will post in the next week or so with the results.

 

[steelespike]

Thanks,
What size prop did they give you?

 

[ddh1961]

They originally gave me a 12.5x19 4-blade Spitfire, but after doing some research that pitch seemed extreme so I took it back & bought a 13.8x13 Spitfire, which is the prop recommended by the Mercury prop selector. Tested it over the weekend with our usual load onboard (approx 800 lbs of people, gas, & gear) and the best we got was 15-16 mph (GPS) at 4200 rpm. Losing out on 1800 rpm worth of power, so I'm going to try & find a local prop shop that will give me a good recommendation & let me return whatever they sell me if it doesn't deliver...