Prop pitch?

[shuswap outdoors]

Hey guys have a 50hp honda with the stock 13p 3 blade prop. No rpm gauge.

Solo with gear it does 33mph
2 with gear it does 33mph
3 with gear it does 32mph
4 with gear it does 31mph

Im guessing with small loss of speed i have room rpm wise to move up to a 14 or 15p? Also thinking of switching to a 4 blade?

I have a kicker so the main is just to get me from point a to point b so more speed the better.

Any opinions?

Thanks

 

[ericl]

If you refuse to check RPM, then you should assume that someone who knew what they were doing chose the prop you have. Sounds like you are not over propped. I would find out if your motor has an RPM limiter. Most info on prop changes indicate over propping leads to engine damage. 4 blades tend to perform better at low-mid speeds & a 3 blade will give better top speed because of less drag. If you muck around with this realize that recommendations for displacement hulls are different from planing hulls.

 

[AlK]

You need to know the maximum rpm for your engine and have an rpm gauge to make the proper decision as far as the prop size goes.

 

[Damien]

+3 on knowing your RPM and engine limit.

4 blade will not make you go faster. Anyway you slice it or dwell on it, I think you are right at your max speed. +/- 1 to 2 MPH.

Is it worth the effort? Here's a quick thing to think about. For ease of math, say you are making a long 32 MILE RUN at 32MPH.

If you travel at 34MPH, you'd make the same run about 6 minutes faster.

I would suspect most of your runs are much less than 32 miles. Therefore, the actual time saved is substantially less than 6 minutes in practical application. Meanwhile, running at WOT/MAX RPM isn't always the best thing either.

 

[shuswap outdoors]

If you refuse to check RPM, then you should assume that someone who knew what they were doing chose the prop you have. Sounds like you are not over propped. I would find out if your motor has an RPM limiter. Most info on prop changes indicate over propping leads to engine damage. 4 blades tend to perform better at low-mid speeds & a 3 blade will give better top speed because of less drag. If you muck around with this realize that recommendations for displacement hulls are different from planing hulls.

Im not refusing to check rpm, there aren't any cheap options that work with my honda other then a honda gauge itself for a few hundred dollars. Tiny tachs dont work with the honda 50. Just looking for experienced

+3 on knowing your RPM and engine limit.

4 blade will not make you go faster. Anyway you slice it or dwell on it, I think you are right at your max speed. +/- 1 to 2 MPH.

Is it worth the effort? Here's a quick thing to think about. For ease of math, say you are making a long 32 MILE RUN at 32MPH.

If you travel at 34MPH, you'd make the same run about 6 minutes faster.

I would suspect most of your runs are much less than 32 miles. Therefore, the actual time saved is substantially less than 6 minutes in practical application. Meanwhile, running at WOT/MAX RPM isn't always the best thing either.

Great point

 

[tubber]

Hey guys have a 50hp honda with the stock 13p 3 blade prop. No rpm gauge.

Solo with gear it does 33mph
2 with gear it does 33mph
3 with gear it does 32mph
4 with gear it does 31mph

Im guessing with small loss of speed i have room rpm wise to move up to a 14 or 15p? Also thinking of switching to a 4 blade?

I have a kicker so the main is just to get me from point a to point b so more speed the better.

Any opinions?

Thanks

I think you are doing fine and don't need to change anything unless you start towing (small) people behind the boat.
I have a 50hp on a 17' whaler and you are going about 3 mph faster solo, and way better with 3 people.

 

[trophywife]

sounds like it is doing what it should..