questions on propping my boat

Hey guys,
I’ve got an 18′ Crestliner Tournament Series boat with a 150 VMAX Yamaha. I’ve currently got a 19 pitch prop on, and I don’t remember what my max RPMs are, but my max speed is only 42. I tried my buddy Chris’ (sharkbait on IDO) 4 blade prop, and I believe it’s the same pitch or very close. Max speed is real close to the same, top RPMs were 4700.

So here are the questions. What does a 4 blade prop do for you that a 3 blade can’t/won’t? The only thing I know is that it’ll give you better handling in corners (I think), but that’s about it.

Also, how do I find out what the max prop is that this engine will push? Would I try going to a 21 to see how it does? Or more?

I’m mostly curious to see what kind of speed I can get out of this boat, and to make it the most efficient.

Propping is one thing I’ve never really been too good at, so I’m eager to learn more about this. Thanks–

really need to understand how many rpm’s you are turning at wide open to help much.

As a guideline you drop 200 R’s for every inch of pitch that you increas and you increase 200 R’s for every pitch you decrease.

A four blade prop of similiar pitch and diameter will turn less R’s than a three due to an additional blade in the water.

Good luck Ben!

-ted

You should be running closer to 5700 rpms. You need to drop pitch.

A 4 blade prop will generally give you a better overall bow lift. And as you mentioned better bite in a hard turn.

-J.

You’re saying I should drop in pitch from a 19 and go down? If I want more speed, I know I’ll have to go up, but I’ll also drop RPMs. Is it going to be impossible for me to get more speed out of this motor?

If you are turning a max of 4700 on the 4 blade 19, I doubt you are doing much over 5000 on a 3 blade, but you need to find out what the actual max is to get the right prop. Just for reference, I am running an alumacraft navigator sport 175 with a 150 e-tec. They originally put a 21 pitch prop on it, which was pushing it at 52+ at a max RPM of 4950, which was about 700 too low according to evinrude. I raised the motor, and dropped to a 19. I was able to bump the RPM to 4600, which is close enough for me, and my max speed dropped to about 50.

Running to much prop and being 1000 RPM under the recommended WOT range is pretty hard on your motor over time from what I’ve read and been told.

Getting the boat propped correctly is kind of like black magic. Try to find someplace that will let you test drive a bunch of different props and see what works best.

Need more info as mentioned by Ted and JJ. Like what diameter is your prop, top RPM, at what speed GPS. What hole is your motor in.

Lugging any engine is not good for it your power band is right at the top of your RPM range and that is where she needs to run.

I run a 182 TS with an Opti 135 one very rare occation I touched 50 MPH GPS. Usually run 46 to 48 MPH GPS. at 5,750 RPM right at where my motor should run. I luv my Power tech 14 X 19 3 blade. It has real hard cupping and it handles like no other prop I have run. Does not blow out in waves some on sharp turns but not bad I can stay on plane down to 18 MPH GPS,

Edited to add. Yamaha made two gear cases for that engine one had 1.86 gears max RPM 4500-6000. And 2.0 max RPMS 4500-5500. Best place to start what gear case your running.

Thanks guys, this is some good info that I appreciate. I hope to get the boat out again next week to see what my max RPMs are with the 3 blade, but check out our weather.

I hate this weather

I’m guessing it’s not too far off from the 4700 RPMs that I saw with the 4 blade. I guess I just never really look at the gauge, but I’ll try to get out soon.

I’ll see what my serial numbers tell me today about the gearcase. I don’t know that it matters, but the engine is not the HPDI, but the OX66 FI model. Thanks again-

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I hope to get the boat out again next week to see what my max RPMs are with the 3 blade, but check out our weather.

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Tuesday looks nice.

At 4700 rpm, you are not into the meat of the horse power range. That motor will run at 6k all day long. You want to target 5600-5800 rpms to hit the 150hp + that motor can put out. At 4700 you are bogging it down and probably only putting out 125-135hp and using a lot of gas to do it!

-J.

I haven’t paid quite as much attention to the Vmax OX66 150, ( I have a 200) but I hear lots of people say run the 200s to 6K and from what I’ve seen and read that seems well accepted. Myself if or when I try at reproping my boat again will shoot for the 5700-5800 range.

Vmax motor are interesting, unlike others, they really do pick up more power the faster you spin them, that can’t be said for all motors.

Also the cooler it gets you see less rpm than you will in summer, denser water, most boats pick up a 100-200 rpms in hot summer water.

You really should be spinning that motor faster Not totally sure about your setup either motor a higher height may help you spin it faster, but that isn’t always just an easy raise the motor a notch, that could included reproping and such to make the boat still handle. Eitherway it’s certainly something that should be looked into.

I should also mention Have you ever checked you O2 sensor? or cleaned it? The rpm seem low, I think you should be going faster and spinning it higher at current setup, but it’s hard to say for sure. I’d at very least clean and check you O2 sensor.

A wealth of info to be found on BBC, http://bbcboards.zeroforum.com/zeroforum?id=54

Thanks guys, I haven’t forgotten about this. The weather really took a dump on us down there this week, so I don’t know when I’ll get out again to see what my RPMs are with the 3 blade, but hopefully it’ll be soon. I really wanna get this figured out. Thanks again for your help, and I’ll be calling on you again soon–

Just for reference, it took me two months, 4 different props, and three different engine positions to get my WOT RPMs close to what Evinrude recommended. It may take you a few tries.

Thanks for the encouragement, Eye. That’s exactly what I’ve been expecting; not an easy process. Wrong time of the year for me to get this started, but ya gotta start somewhere.

Hey guys,
went out to the garage and got some numbers today to see what they can tell us. The post about the different gear cases is stuck in my mind because I don’t know how to tell which one I’ve got. Here are the numbers off the engine.

VX150TLRY (I have a list that tells me what those are, things like power trim,etc)
Then the tag has 6J9 L000908
And to the bottom right of the last number, there’s a ‘T’

Does that help? It was manufactured 3/99.

I also took a few pics of both props on the boat, just so you can see the spacing of each. The 3 blade is pretty closer to the cavitation plate, while the 4 blade is just a bit farther away, so there’s a bit more space away from the plate.
I don’t know what brand or anything either is, so here’s the numbers off the 3 blade:
15 1/4×19-M -and 19-M is also stamped on the outside of the prop. It’s got a black line on one side of the prop, you might be able to see it.

The 4 blade has the following: F2254 H 01515

I believe it’s an ‘H’, but it’s pretty thin. Doesn’t quite look like a ‘4’.
Also, on the 4 blade, you can sorta see down the inside of the mounting hub that there are only splines near the back of the prop, not the whole way through. There’s a notch that you can feel with a screwdriver, so I don’t know if it comes out of the hub or what.

The motor seems to be in the right holes on the transom because when I hit the trim, you can really feel it accelerate. I added a couple of those pics as well.

1st pic is the 3 blade, 2nd is the 4 blade.

Looking forward to any help you guys can add. Thanks again–

First off the “m” prop is a yamaha prop. No idea about the second prop…

Secondly I really think you should look at moving that motor up, I have a feeling it you can really feel it accelerate that’s saying too much drag, and the motor need to go higher, and you’re only seeing 4700 rpms, with you motor as low as it will go. Efficiency, and speed should both go up with the motor, in my head anyways.

I’m also going to venture some guesses from things I’ve read, some Crestliner (IIRC) I remember people complaining about porpoising, trimming down and lowering motors tend to minimize that, but IIRC, people have added hydrofoils and I specifically remember some people singing the praise of trim tabs, solving the porpoising problems with no ill effects. (walleye centralpost IIRC) So I’m not convinced it’s just an accidental “poor” setup or if someone moved it to such because of other issues.

In any case *I* would try moving the motor up myself, before I even attempted proping it.

Can you find others with the same boat and motor and see where there have they’re motor height and props?

Of course I’d like to see others weigh in on the subject, I haven’t done much myself with proping and setting up, but I’ve done (alot) of reading up.

Please don’t take my comments the wrong way, I’m trying to be helpful and not trying to bash crestliner or anyone.

I agree with Nick that you should try raising the motor. I have mine on the third hole down. It was mounted on the bottom hole from the dealer, and the RPMs were low. I would raise it, test it, raise it, test it, etc. The bottom hole caused it to blow out in turns and when trimmed up. Going back to the third hole seemed to be the sweet spot for me. I gained about 200-300 RPM from raising the motor, but was looking to gain 700. Switched my prop from a 21 to a 19 and gained about 300 more. I am still about 100 short(5600 instead of 5700), but it is close enough for me. I’m running a different rig though, so it may be different for you.

You can raise the motor easy enough on your own just using the trailer jack. Just be careful when you crank the jack that the motor is moving freely enough. I caught the transom cap and bent the SH*& out of it.

Wow, 2 for 2 on saying raise the motor. I can tell you that when I’m on the water, the motor is real closer to the water, that’s for sure. I’ve got a hoist in my garage, so I’m sure I could do it myself.

I’ll make it out either today or sometime later this week, and I’ll try to get better pictures of the motor trimmed down while on the trailer, so hopefully I can get a better angle and better look at the height.

This is sorta confusing me too. Just so I’m straight, tell me if I’m correct on the following:

going down in pitch will get higher RPMs, but won’t increase speed. If I got up in pitch, I’d go faster, but it would be hard to get higher RPMs.

That’s my thinking anyways.

I think the rule of thumb for pitch is for every inch you go up, your RPMs will go down by 200. Every inch you go down, RPMs go up. I could be wrong on the number of RPMs, but I know for sure that going down in pitch raises your RPM and vice versa with going up in pitch.

The way I understand optimum motor height, and I again I could be wrong (I have two ex-wives that told me I was wrong all the time), you should have your motor set so that when the boat is on plane and the motor is trimmed up where it belongs, the cavitation plate should be visible, with the water hitting the underside of the plate.

The attached link is to a prop gods post that has pictures of what it should look like.

Prop gods post

I think part of whats not helping is the one prop is a 15 inch diameter. On that rig I beleive a 3 blade 14″ diameter with a 19 pitch with a good hard cup would get you darn close maybe a 20 with the motor raised. That 15″ diameter on that boat I beleive is a killer way to much blade surface. Usually larger diameter is for very heavy boats.

Going up in pitch does not mean faster if the engine can`t turn it.

definitely raise the motor up and this will help you gain more rpm’s and if your rig porpoises (sp?) you may need to add a hydrofoil – no big deal I did it on several of my Rangers so I could get them to run where I wanted them to. Also pay attention to prop diameter also as you go up and down in pitch if your diameter changes this is another variable to take into account.

Just for conversation – I have an F150 on my 22′ pontoon turning a 15 pitch prop(3 blade YAMAHA Reliance series) that runs almost 6K with just me an my two labs in it.

On my 620T I have a 150 E-TEC that I am turning either a 17 or 18 pitch 4 blade BRP Cyclone depending on the load in the boat – but those two props behave very differently as the are different diameters by either 1/4 or 1/2″…

Lots of variables here for you to work with.

Let us know if you have further questions.

-ted

Hey guys,
First of all, thanks for hangin with me during this entire process. I knew it wouldn’t be easy when I started, but I’m hoping info from yesterday will tell us something.

RPMs with just me in the boat, full speed and totally trimmed was only 49-50. I looked at the motor and couldn’t see the cavitation plate at all. Lookin like moving the motor up a hole is going to be the first place to start -would you agree?

I’ve never done this before. Will moving the motor up just one hole really make that much difference? Looks like the winch hanging in the garage might come in real handy.

Yes and Yes.

-J.

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Looks like the winch hanging in the garage might come in real handy.

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You really don’t need a hoist. An extra set of hands is all.

Block the tires so the boat does not move. Lower the trailer jack all the way down. Then trim the motor full down. Place a small piece of 2×4 under the skag. Slowly lift the trailer jack until the the skag is firmly pressed to the 2×4 on the floor. Next, remove the 4 bolts from the motor/transom. With your extra set of hand holding on to the motor, slowly lift the trailer jack. This pushes the transom down and motor holes up. Continue slowly until the bolt holes are aligned with the next set of holes. Apply a generous amount of marine silicone to the holes, insert bolts and tighten. (I believe the torque specs are 60 lbs, but check that.)

-J.

Ok, here’s an update. My buddy Jay came over today and helped me take the bolts out, and we moved the motor up a hole to see what it’ll do. After talking to the local expert, and hearing him echo Jay and what’s been said here, I figured it’ll be worth a try. While hanging on the boat, the angle already looks better and looks like maybe it did need to come up. We’ll give it a spin Monday and see if it improves. I gotta think it will.

Neat, I would raise consider raising it another hole if everything goes well on the test run, you might find a point where you feel it’s too high or your lacking bite or speed or handling , then a prop change may make all the difference in the world, I’d expect the 4 blade to bite and turn better than the 3 blade, probably a little slower than the 3 blade too, you should consider bringing them both and running them both. Once you can figure out the motor height, propping would be my next step. (providing you don’t need/want trim tabs/stabilizer) IMHO.

Keep us(me) posted I really think that boat will do a close to 50, and overall Gas mileage should go up too.

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you should consider bringing them both and running them both.

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Thanks! I’m way ahead of ya…I’m definitely going to run both and see what kind of difference it makes, as I’m very curious. I’m thinking there’s gotta be an improvement. If I got 50 out of this boat/motor, I’d be VERY happy!

Here’s another thought I had: Now that the motor has been moved up, I’ve got a larger space between the top of the transom and the mounting bracket on the motor (I hope that’s descriptive enough to give you an idea). Do I need to worry about that at all? Or do I need some sort of spacer in there to take up that space?

The motor does not need to “sit” or be supported on the upper surface of the transom, the bolts do all the work. No need to fill the gap.
HRG

Ok, here’s the latest. Just got back from the lake, and raising my motor a hole didn’t do jack, basically. My top speed was 42.18, and my RPMs touched 51 once. I couldn’t see my cavitation plate again either at WOT. What do you think? Raise it another hole? Go extreme and raise it two?