2100sx boat prop

[chap2100]

I have a 89 2100sx w/ a350 magnum (270) engine. I was looking 4 a new prop for her come this spring. I am curious as to what other folks have and how they like it. Now I have 14x19 prop and I am turning it too fast (4900 rpm). Not sure who makes it. thoughts?

 

[TilliamWe]

Re: 2100sx boat prop

The answer all depends on what you are trying to gain. If you want all out top speed, try a 21pitch 3 blade. If you want better hole shot, try a 20pitch 4 or 5 blade.
If you were in Central FL, my dad has an OLD 22pitch Turbo 3 blade that he has put on at least half a dozen different boats that has improved their performance.
What is the MAX WOT rpm range of that motor? And are you "sure" the tachometer is correct?

 

[chap2100]

Re: 2100sx boat prop

I am looking for best cruising mpg. This model boat has a small fuel tank. (22gal). I checked the tach with my digital meter and it was within 50 rpm. The boat tach actually read 50 rpm low! So I am turning the motor almost 5000 rpm. the range on my engine is 4200-4600 rpm. I guess i need to lower the rpm by 500. I know all props manufacturers are different. I was thinking about a 3 blade 21 pitch that has good bow lift. Although I'd be very interested to see if I could turn a 22 w/out bogging down the motor. Thoughts?

 

[TilliamWe]

Re: 2100sx boat prop

There are a lot of factors that can change from one manufacturer to the next. But, yes you should be able to turn a 22 pitch prop.
If you have done all your WOT RPM testing with the normal load you are going to have aboard, then a 22 seems just about right. If you have just had yourself aboard and you normally have 3-4 people, then a 21 should do it.
If you are only interested in cruising efficiency, then you might consider a 4 or 5 blade prop. They would raise the stern out of the water higher, allowing you to trim the bow up "more" and therefore you would have less hull in the water, and less drag.
You might post this in the prop section, with a lot of details, and there are some professional prop guys that might have specific prop suggestions for you.

 

[a70eliminator]

Re: 2100sx boat prop

Chap 2100 that must be a strong motor, I have a 1990 chap2000sl similar boat but 20 footer version, it has a 351Ford 5.8 I had to put a 14x18 prop to get 4400 loaded. A 21 pitch would be too much pitch for my set-up.

 

[TilliamWe]

Re: 2100sx boat prop

Those 351s were rated at 228hp, the 270 Mercruiser was rated at 270, so yes, it's a stronger motor.

 

[Mkos1980]

Re: 2100sx boat prop

I PM'ed you but I have tried about a dozen props on my 2150SX (same boat but a cuddy) The fastest prop and best cruiser prop hands down was the Laser II 21P ,ve tried Hydromotive 22's Mirage 21, 23's Vengeances, solas's, and many other 3 and 4 blade units. The fastest out of the hole was the Hydromotive 22 though. It was on plane in 1 sec but I had to keep the rpms up to get a cruise.