20SLV Yam F90 prop selection

Hmsmx66

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I have a 2019 20SLV Yamaha F90. Current Prop is a 13 1/2 X 12-K that came stock. Interested to see what others are doing with prop selection. First time out only get 23 mph with 3 people on boat on perfect water. RPM are about 5700-5800. Seems others are getting better speeds then that. I had 5 people on it this weekend and barely got 20 mph. If I go with stainless should keep same size or change. Would 4 blades do anything. Anyone else with same setup getting better speeds? Thanks for help.
 

Titletown Mike

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I have a 20 SSX with a 90hp with a 4 blade prop. I get about 22-24 mph depending on waves/wind at the same RPMs.
When I have a full gas tank, 4-6 people, coolers, etc. I get about 18 mph.
With such a small motor (90 hp), stainless or aluminum, 3 or 4 blade, you won't see much in mph outside of 1-2 mphs at most. I switched to the 4-blade, not to increase speed, but to get a better hole shot. Maybe its just me, but it also seems like I have more thrust control when maneuvering near docks.

I think you are pretty much stuck in the low 20's for mph.
 

Vikingstaff

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4 blades is better for hole shot, 3 blade typically better for top end speed. Do you have 2 pontoons, or SPS tritoon? Do you have lifting strakes? Those would be major factors in potentially accounting for the performance you are seeing. Without both, I am not sure you can expect too much more in performance. If you have both, then yes, something is off. However, I don’t know your motor RPM range or good prop ideas on a 90HP. I am sure others with something similar can provide some good advice. Happy Boating!
 

Hmsmx66

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4 blades is better for hole shot, 3 blade typically better for top end speed. Do you have 2 pontoons, or SPS tritoon? Do you have lifting strakes? Those would be major factors in potentially accounting for the performance you are seeing. Without both, I am not sure you can expect too much more in performance. If you have both, then yes, something is off. However, I don’t know your motor RPM range or good prop ideas on a 90HP. I am sure others with something similar can provide some good advice. Happy Boating!
Thanks for the info. I do not have any lifting stakes and only have 2 23" toons.
 

Vikingstaff

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Thanks for the info. I do not have any lifting stakes and only have 2 23" toons.
That is probably the main issue, and no getting around that. I looked at the RPM range for the Yamaha f90, and it is 5000-6000. With you at 5700-5800 now on a light load, I don’t think you have room to go up any pitch in prop. At most you could go up to a 13p, and it would either top you out on RPM’s or put you slightly over (which you don’t want).

About the only other wiggle room you might have is if they mounted your motor too low in the water, and you have excess drag. But again, I since you don’t have lifting strakes or a tritoon, I think you are probably not going to see much or any more speed.
 

PartyBarge

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Your pontoon is very similar to ours. I'm surprised you were not way over-reving with a 12p prop. We used to hit 6300 with a K-series prop of 13p. Maybe the motor is set low? Anyway, our switch to the 4-blade Quicksilver Nemesis 13p was a great move...better than any k-series of 13 through 15p (have a friendly dealer). All of them had very high calculated slip, the pontoon specific Nemesis cut that by more than half. As noted above, the speed may not increase by much (we run 20 to 26 depending on load/conditions), but handling and acceleration will be way better.
 
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