Prop size

[TeeKay]

For those who have 21 ft CCs with 150s what size props are you running? I have a 94 carb'd 150 with a three blade 15-38 x 11 on my 2100. At WOT throttle I'm turning 5800-6000 rpm at 28 knots and cruise at 4300 rpm moving about 22 knots After reading some performance numbers on here and Yamaha performance reviews I'm thinking I'm under pitched. Any ideas?

Thanks

 

[Brad 21se]

I have the same engine (just a newer version) and run a Michigan Wheel Apollo SS prop - 14 3/8x15p

WOT is with a clean bottom in the Spring is 5400 at about 41mph (GPS). Cruise at around 3700 doing 28mph. My 21se has a T-top/curtains which I am sure induce some drag.

 

[TeeKay]

Brad,

Is the prop you're running a 3 or four blade? Im going to reprop but I just want to make the right call. I think I might look for a 14-1/2x16 three blade. I run with a full tank but I don't have a t-top and it's usually just myself or one other person on board.

-Tom

 

[Bryan 2530]

Yeah, 11 pitch is too low for that boat.

That is like driving your car around in 1st gear.

You should be around 15 pitch or so.

 

[TeeKay]

Do you think if I change the pitch I should get a smaller diameter prop also? It has a 15-3/8 now so it's quite a bit. I don't want to get more pitch on a big prop and lose too many rpm'S

 

[Bryan 2530]

Is it Aluminum or SS???

It's really hard to say, there are more variables at play than just the prop.

Weight, expected load, sea conditions, etc. etc. etc.

 

[TeeKay]

SS for sure. I usually have a full tank, one other guy and about 200 lbs of gear. Im out on the west coast at the channel islands and there's usually some swell and wind in the afternoon. I know I need to check the outboard when I'm running and see if I need to raise the motor since its mounted on the top hole.

 

[Brad 21se]

My current prop is a 3 blade.

The prop that originally came with the boat was a Yamaha SS 3 blade, but it was a 17 pitch. WOT was only 5100, so I swapped props to get the rpm's up closer to max for my engine (4500-5500 according to Yamaha). 2-strokes seem happier running at the upper end of the range

 

[TeeKay]

Cool, thanks for the input. I talked to a guy at a shop here and he recommends going with a 15 inch x 15 pitch so i'm thinking about going with that. Im going to look around for some other deals on props in my area before pulling the trigger though.

 

[Brent]

You can check with Ken at PropGods and their forums.

 

[Brad 21se]

My engine would also benefit from being raised one hole, but due to the way Parker drilled the transom, that's not possible. Looking in the bilge, the clearance is fine for the bottom holes. If they had been drilled higher, I would be able to raise the engine. Oh well

I bet I could run a 17 pitch if my engine height was dailed in better.

 

[TeeKay]

I wanted to raise my motor too but the bottom bolts are drilled through the transom and mounted as low as possible on te transom assembly so it will have to stay

 

[Bryan 2530]

Drill new holes.

 

[Brad 21se]

Sure, I could drill new holes but the boat performs fine. I would consider playing with engine height if it didn't require filling old holes/drilling new ones. I'd rather just go fishing