Want more RPM

[Real1]

I have a 18 1/5 foot aluminium fishing boat with a full windshield. It is a modified V hull powered by a 4 stroke 200HP Mercury V8 Pro XS. Right now I'm using a Tempest plus (19P) and getting a maximum speed of 56 mph at 5700 rpm. I'm satisfied with the performance but I feel I should be turning more RPM's.
I'm looking at a Revolution 4 17P that is available now or at a Tempest + 17P that is out of stock and available much later in the year. Will going to one of these two props get me the 300 to 400 rpm that I want without loosing speed ?

[Snowking]

Four blade rev 4 17 pitch prop will run close to the same rpms as three blade tempest 19 prop. I have run both on a 150. Except for the bravo 1 fs props. It is common for four blade props to run less rpms at a certain pitch. Then three blades at the same pitch.

[REW]

Real,
You are right at the tipping point.

If you pitch down - in theory you lose speed.

But, if you pitch down you gain rpm.

The question is simply this - does the rpm increase compensate for the lower pitch of the prop.

MAYBE

Normally, when you pitch down you are often going for the low end hole shot and are willing to give up on some top speed.

So, my guess is that if you pitch down to a 17 you will likely really go to a head snapping hole shot with little change in top speed, except spinning your engine 300 rpm faster.

The flip side of the argument, is that if you need to make long runs at 3/4 throttle for better fuel economy - you will put more miles behind you running the higher pitch prop at the same rpm. i.e. if you cruising speed is 4,000 rpm and you run the 19 pitch at 4000 rpm and also run the 17 pitch prop at the identical 4,000 rpm, the run with the 19 pitch prop is going to get you there first.

In past years, when I knew that I was going to make some really long runs to get somewhere, but also knew that I was not going to have to be doing a bunch of stops and starts - I would often pitch up, even though I wasn't really able to turn the prop.

I would pitch up, until I had a pretty poor hole shot, but after finally getting on plane, I could throttle back and really put the miles behind me at the same speed with much less fuel.

So - as with anything in life and particularly in boats and motors - it is a trade off.

Every motor is different.
Every hull is different.
Every prop is different.

So to answer your question, the only way that you will know the final answer is to get any and all props that you want to try, and put them on your engine and put 10 miles on each prop - running from a standing start, rough water, smooth water low speed, mid

range and high speed.

Take good notes, along with stop watch time for hole shot and gps speed readings - both downwind and upwind.

Then, remove prop 1, and repeat the test with prop 2.

Repeat with prop 3,4,5,6,7, etc.

Then and only then - will you have the knowledge and data that you can speak with authority about the particular attributes of each prop. You can also make note of short comings as well as strong points with each prop.

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Every time that I had a different boat or motor - I would initially try to optimize the rig for top speed. But, over time I learned that top speed is only one attribute that one needs in the boat and motor combo. For most folks, for most rigs over the long term - many many folks back away from the top speed criteria and rather focus on low end hole shot, as well as mid range cruising speed performance. Also, many folks simply want the overall best handling and smoothest ride possible along with the very best hole shot possible --- even at the expense of top speed.

Then, if you throw water sports into the equation, the prop will be tailored even more for load hauling and hole shot and mid range pulling performance - rather than top speed.

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Finally consider the waters on which you use your rig.
If every day that you go out, you are faced with 1-3 foot waves - it doesn't make sense that you are going to hammer up your boat and hammer up your self and passengers by trying to run wide open - smashing into every wave face to the detriment of both long lasing durability of your boat as well as long lasting durability of your back, ribs, knees and the rest of your bodies and kidneys.

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I have no idea of your age, but most folks like to live a long, healthy life FREE OF PAIN - that could very well be caused by taking on too many waves, and ripping up knees, portions of your back skeletal structure or even internal organs like kidneys.

Your rig, your choice.

Enjoy and if you need to know - test, test, test.

Best wishes

[Real1]

Thank you REW


Yes, I'm at the turning point. Even more so because I'm getting a good holeshot with the Tempest 19. The boat lays down around 3500 to 3800 rpm so I'm good with that. Yes I'm old but young at heart and want to get the most out of my boat and motor. I fish on large bodies of water so top speed is important.
If I go to a Tempest plus 17 P, I kinda know what to expect. More rpm but less speed with the same caracteristics.

What I really want to know is if a prop like the Revolution 4 with more sternlift would compensate on a boat like mine ( no pad) for the loss of speed of a 4 blade. Would lifting the stern higher make it go a little faster ? The motor is mounted in the third hole from the top (in the middle).
And yes, I will be trying different props.

[jjy]

Based on my experience, a tempest with a lot of bow lift is generally a fast prop. The 4 blade props are normally better at low speed planing, handling, and grip. If you want more rpm try raising your motor one more hole. Another prop that is quite fast is the enertia based on my testing. The 19p enertia will turn higher rpm than the 19p tempest and possibly more speed. I run a 18p enertia and 19p tempest currently. Props vary but my 18p enertia runs 6200 rpm 56-57mph vs my tempest 19 5950rpm 57.5mph. I need to try a 19p enertia yet and retest both props since I raised my motor up a hole.

[Northwoodswalleye]

Another choice is a bravo LT 19p. At the correct height it should run 1-200 more rpm than the tempest. I’ve got a ranger with v8 proxs and went from a 23p bravo FS to a 21p rev4 and the rev4 needs to be ran a full 1” deeper for optimal performance. Very similar rpm between the two

[REW]

If you want more rpm and want to check the ability of the motor to spin up, put on a 3 blade 15 pitch prop and you should be able to easily turn over 6000 rpm. Also, this is a wonderful stump pulling prop and should give you head snapping hole shot with a top speed about 8 mph less than what you are running now.

[muskyed]

Not all props the same. With Bravo props, mercury recommends pitching up one inch vs a tempest 3 blade or similar style to keep same rpm. REV 4, different ballgame, they recommend pitching down 1" for same rpm.

Why would you want more RPMs? I'm sure you are burning a ton of gas already at 5700 RPM.

How often do you even run full throttle?

Are you fishing or racing?

[plnwtf]

Why would you want more RPM and the same speed? Lower RPM is easier on the motor and the pocket book.