what prop rt188/90hp sho

[blades31860]

could use a little help on this, its a friends boat, bought used no engine, he wanted a 90 sho, so that's what I put on it, have 8 hr on engine and trying to find props that works the best is rather difficult when no one has one to test, first prop was an Alun 13,1/8x17 to break in engine, you could hit rev limiter pretty easy, barrowed a laser2 13 1/2x 22 just to see what it would do, it turns 5200 and runs 42 mph gps, full of gearing 2 people 5025lb of fat LOL, boat handles nice with the laser and lifts at lower speeds than the alum, I found a laser2 13 1/4x19 new for sale but keep looking at power tech nsr3 13 1/4x19, speed is not the main concern here ,he fishes small lakes and usually fishes alone, he keeps quite a bit of weight in it aprox 200 lb of crap including fishing gear ,he's old school he has a lot of tools in boat, runs 4 group 24 batteries, what prop do you think is best

[tcesni]

Do you know the gear ratio on this motor? I run a 90 Opti on my RT188 and with more info I might be able to provide an educated guess.

[blades31860]

2.33

[tcesni]

2.33

That is the same ratio in my 90 Optimax with a maximum rpm of 5750. I run a 22" Laser 2 prop with extra cup added by Mark Croxton. I had this motor on a previous boat as I probably need either a 20" or 21" pitch. My maximum rpms by myself are 5400. So I think you would need a 20" pitch stainless prop given all the weight in that boat (4 batteries!!!).

[Extremeboating]

The max RPM output on that 90 HP is 6000 RPM. You are way low on that powerband and could easily make more out of it. A 19 would make you 5800 and keep you moving nicely around the water and keep you at the right range of that powerband.

[tcesni]

The max RPM output on that 90 HP is 6000 RPM. You are way low on that powerband and could easily make more out of it. A 19 would make you 5800 and keep you moving nicely around the water and keep you at the right range of that powerband.

I agree.

[GeauxTide]

I agree that a 19" would be the ticket. I strongly suggest a 4 blade with this hull. My X7 has been superb at hole #3.

[Extremeboating]

I agree that a 19" would be the ticket. I strongly suggest a 4 blade with this hull. My X7 has been superb at hole #3.

I agree with this also. Throwing down that much HP you should be using a 4 blade to minimize propeller slippage, maximize holeshot, decrease speed required to plane, and increase steering responsiveness under speed. The Spitfire X7 is the big brother to the Trophy Sport and I absolutely LOVE my Trophy Sport propeller. I don't think I'll ever go back to a 3 blade again actually.

[blades31860]

well found what I believe is the right prop for this combo power tech nsr3 13.250x19 boat runs pretty good plenty of lift and boat runs 5900-6000 at 42 mph with a 90 hp I don't think I could ask for more, maybe a 4 blade would have given a little more lift?

[tcesni]

Those numbers look pretty good to me.