Prop help

Ron Geisler

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New boat owner, i have a bennington 22ssx, cant get over 20 mph. Have a yamaha 90. Have a aluminum prop 13.5 x 14. If I drop diameter to 13 and increase pitch to 15, would that help with my top speed.?
 
What is your WOT rpm?
 
What speed were you expecting? How many people and how much fuel and gear was onboard when you hit 20? You might be expecting too much from a 90hp. I've yet to meet one that went over 22.

If you are close to the right prop, there isn't a change that will yield anything drastic and any improvement in any area is taken away from some other area.
 
My 1st Bennington I had a 22 SLX 2 tubes with a wave shield and a Merc 90.Prop was a Spitfire ,4 blade ( I dont recall the dimensions ) I was able to hit 28
 
  • I have a 20SSX , two 25" tubes , and a 90 Yamaha. Boat came with a 13.5x15 prop. Can't get past 5000 rpm with it and I can hit 26+ on gps with 2-3 people on board and not a lot of gear like packed coolers.
  • Tried 2 other props a buddy had but didn't have the gps installed when we tested em. One , a 14x11 , nice hole shot but hit the rev limiter and felt slower on the top end. The other , a 13 5/8x13 , ran really good and put me right at 6000 rpm with the same load on the boat and really felt good on the top end. The dealer is exchanging props for me and it'll be here this coming week and I'll be able to get numbers off the gps then. I believe it'll run in that 28 mph range no problem.
  • Even going smaller diameter , I think the 15 is too much pitch for a 90. I also believe you are going the wrong way with a smaller diameter for a pontoon prop. That's my amateur opinion anyway.
 
Well a little bit more on my prop testing.

Put the 13 5/8 x 13 on again today and had 4 people on the boat...first tested it with only 2 people on board. Rpm's were up at the 6000 mark and maybe a touch more at times. No appreciable gain in speed , and a lot of cavitation. Moved people around to different spots on the boat and could not trim up or down to get the cavitation to stop. Not what I was hoping for so I'm back to square one.

I was hoping for better info for you Ron with hopes of it helping you out some. I'll have to get on the phone in the morning and talk to the local prop shop where they really know their stuff and see what the dealer says about it as well and as I make progress I'll update it here...
 
If you are getting Cavitation with the motor trimmed down , Them possible you motor is mounted too high on the transom. What holes are your top motor mounting bolts located in?
 
Pictures?
 
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