Correct prop pitch - Striper Talk Striped Bass Fishing, Surfcasting, Boating

Elmo · 08-15-2011, 04:46 PM

Anyone own a HS 23 WAC with 200hp? If so, I would be curious to know what size and pitch prob you use. Mine (yr 2000) came with a 15inch, 17 pitch prop on it but I notice I don't achieve the rpms noted for the engine in the manual. Range is 5 to 6k and I just make it to 5k wot. I understand if I drop the pitch it will increase roughly 200rpm per degree of pitch. Before I buy a 12,13 pitch prop, (need spare anyway) I would like to know what that will do to speed, fuel economy etc. Anyone have similar style boat/engine or thoughts on this? Thanks in advance.

freebie · 08-15-2011, 06:41 PM

sounds like you need a 15x15 then. when you tested was it just you in the boat? trimmed out correctly? lots of variables that could make you drop rpm's. if your running trim tabs and they are down too far you could lose some also.

Elmo · 08-16-2011, 08:01 AM

Thanks Freebie. I did the test twice and both times I had half tank of gas and 3-4 on board. I did play with trim but did not even think about position of my trim tabs. I will test again and make sure they are all the way up.

Anyone know what happened to thehulltruth site? I figured I would post there as well for some feedback but I can't access the site?

Mr. Sandman · 08-16-2011, 09:21 AM

Big Game · 08-16-2011, 09:53 AM

Mike, do you know if your current prop was cupped? It probably wouldn't make a huge difference, but cupping can lower your WOT RPM a little.

If you go to a 15 x 15, your going to lose a little low end tourque and your holeshot will be slower (the prop wont bite as well), but you'll raise RPM and probably top speed at WOT.

I bet if you had just one or two people on board with light fuel and a light load, trimmed up you'd probably be right around 5500 rpm with your current prop. Then again, I'm certainly not an expert on this stuff.

zacs · 08-16-2011, 10:59 AM

Is there any draw-back to keeping the prop the way it is?

What I mean is he doing any damage to the motor? I ask because I have a friend with a similar situation.

freebie · 08-16-2011, 11:10 AM

Quote:

Originally Posted by Elmo

Thanks Freebie. I did the test twice and both times I had half tank of gas and 3-4 on board. I did play with trim but did not even think about position of my trim tabs. I will test again and make sure they are all the way up.

Anyone know what happened to thehulltruth site? I figured I would post there as well for some feedback but I can't access the site?

you should test with just yourself in the boat with a light load(this means not a ton of gear and less than a half tank of fuel). in that case you would want to be closer to the high side of your range. anything over 5500 should suffice.

Elmo · 08-16-2011, 12:11 PM

Below is what I read initially which says "under normal operating load", which is why I figured I needed at least a half tank of gas/gear and a could more people (normal for me). I will play around with this some more though just to be sure.

From what I have read Zacs, I am making the engine work harder by not being in the optimal rpm range for it. I recently spun the hub of the 15/17 prop, not sure if related or not but it caused me to do this testing to see where I am at.

************************************************** *********
The goal in prop selection is to determine what propeller style and size will maximize performance for your boat, while allowing your engine to operate in the recommended RPM range. The correct propeller will prevent the engine from over-revving, yet allow it to reach the minimum RPM where maximum horsepower is produced.

Run the boat/motor at w.o.t. under normal operating load to determine the maximum RPM you are able to obtain. A tachometer is necessary for this test. Adjust the motor trim angle for the optimum performance. If during this test, you begin to exceed the maximum rated RPM of the engine, reduce throttle setting to a position where maximum RPM is not exceeded.

If your test results in your being able to over-rev the engine, you need to increase the pitch of the propeller. Increasing the pitch increment by 1" will result in approximately 200 RPM drop. If your testing shows, however, that you are only able to obtain a RPM somewhat lower than the maximum rating given by your engine manufacturer, you would need to decrease pitch. Decreasing pitch would increase your RPM.

Elmo · 08-16-2011, 12:27 PM

Sorry George, didn't mean to forget you! Prop is not cupped. Since the boat is not very fast anyway (heavy and single engine) I would be willing to give up a little low end power and hole shot if it make me a little faster across the bay!

ps how was the frozen drink blend off at the YC, did you win again this year? You should post that pic of your boat for the event!

gf2020 · 08-16-2011, 12:35 PM

I would go to a 15.25" X 15 stainless 3-blade.

I can't access thehulltruth.com right now either.

wrench · 08-16-2011, 01:30 PM

you might want to check your engine height first as if it's too low you will lose RPMs there.

Big Game · 08-16-2011, 06:06 PM

We came in third in the blend off....it was a fun night.

Is the prop you have now aluminum? If so, just changing to a SS prop will add RPM. I agree with most of the other posts....a 15 x 15 SS prop (not cupped) should get you where you want to be.

freebie · 08-17-2011, 11:55 AM

Quote:

Originally Posted by Big Game

We came in third in the blend off....it was a fun night.

Is the prop you have now aluminum? If so, just changing to a SS prop will add RPM. I agree with most of the other posts....a 15 x 15 SS prop (not cupped) should get you where you want to be.

going to stainless will drop rpm, it will have less slippage age more rotating mass therefor putting more load on the motor. adding cups will cause it to drop even more