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eyepatrol

Cavitating

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The Alumacraft TS 175 I got last year (with 150 HPDI) has a Hustler prop (aluminum) on it. When planed out and turning, cavitation occurs down at the prop. The prop looses "grip", the rpm's rev up a little and it doesn't perform the way it should.

Is this a prop problem, mounting problem, or something else?

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I think it's a mounting problem, motor might be a little too high. I assume you "played" with trim position, correct ?

Have you considered a stainless steel prop ? I will perform better for your size motor, but if you are fishing shallow or rocky areas or wherever it can get damaged, aluminum is better to avoid damage to lower unit.

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It sounds to me like you might be trimmed up a little too much. When that happens on my boat I knock it down a couple of taps on the trim switch.

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If it only happens when you've trimmed out as far as possible and then made a turn it's pretty normal.

If you think about it, when you're running in a straight line you've got the motor trimmed up as high as possible to prevent porposing and blowing out (cavitating). Then, when you go around a corner the boat leans and half of your prop is deeper in the water and the other half is higher in the water, sucking some air into the prop.

I agree with Valv in regard to a stainless prop with more cupping would probably help, but I don't think that it will completely eliminate the problem. I'd just trim down a little bit before you make a hard corner.

marine_man

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If it happens when turning your motor might be mounted a little high, but I would bet that the right stainless prop would solve your problem and give you better overall performance.

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Like other's have said, could be the motor is too high...

But, I have this exact problem with one of my props, a 3 blade LaserII stainless. In rough sea I couldn't even plane the boat because the prop would blow out. I changed pitch and prop design, and problem went away. I eventually went to a 4 blade SS prop and problem completely solved. More speed, better hole shot and much better lift.

I would get yourself a stainless prop myself, or at least try it as a simple solution. Try a Tempest 19 pitch, it should work with Yamaha just fine from what I've heard. Some dealers might let you experiment with props before buying one...

Stainless props have much better performance than aluminum.

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My apologies guys, I should have been more detailed about this.

The cavitation occurs when the motor is fully trimmed in and the boat is on plane. Doesn't occur so much when I'm traveling around 20mph (just planed out), but when it's pushed up to 25 - 30mph or faster, and I try to do a u-turn, there will be cavitation (and I'm not turning too sharply either). And, the way I get rid of it is to slow the boat down. The motor is not trimmed out at all when the cavitating occurs.

I've wondered if a ss prop would help too. The concern I have is spending money on something that might not solve the problem. Basically, I'd hate to spend money on a ss prop, have the cavitating continue, only to bring the boat back to have the motor re-mounted and find out that was the problem. Then I've spent money on a new prop plus the cost to re-mount the motor. Maybe it's a "necessary evil" though.

Do you guys think a dealer would borrow out a prop for me to test out to see if it solves the problem before he charges me for it? Then if it doesn't solve the problem, return the prop and have the motor re-mounted?

Just thinking out loud here I guess.

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Actually lowering the motor shouldn't take much, they are just 4 bolts.

They hold motor by flywheel, take bolts out lower motor to next hole and reinstall bolts, it will take approx 1/2hour to do. Most important thing is to re-coat bolts with silicone to seal from leaks.

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Quote:

The cavitation occurs when the motor is fully trimmed in and the boat is on plane. Doesn't occur so much when I'm traveling around 20mph (just planed out), but when it's pushed up to 25 - 30mph or faster, and I try to do a u-turn, there will be cavitation (and I'm not turning too sharply either).


If that's the case I agree with the others then... it's either a propping or a motor height issue. What hole is your motor mounted in? As Valv said, it's not too difficult to do either.

Quote:

Do you guys think a dealer would borrow out a prop for me to test out to see if it solves the problem before he charges me for it?


Some dealers will let you do this as long as you give them a credit card, so if something happens to the prop (hit a rock while testing, etc) they aren't stuck with a damaged prop.

The trick to this is finding a dealer that has a good assortment of props to try, or, a buddy that has a prop that you'd like to try.

marine_man

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Eric,

I wouldn't adjust your motor height until you have tried different props. I typically find that most motors are mounted too low if anything. I'm not saying your motor is mounted too low just that I would look at the prop first.

When I was looking at a new boat with a Yamaha motor on it the dealer said he actually had better luck using a Mercury prop in the particular motor I was looking at. If the stainless Yamaha prop doesn't do the trick I would look at some of the Mercury props.

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Thanks for the info guys. In some respects, I'm almost hoping it's a motor mount problem. Might be the cheaper solution. smirk.gif

PS - does a question like this belong in this forum now? I know there is the Equipment/Expert Info forum...but then this is the boats & motors forum. confused.gif

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I had the same problem with cavitation(blow out)with my boat. I had a tempest prop 23" on my triton with a 200 hp opti. I tried 5 different props, and ended up with a REV 4 prop with 23" pitch. I found that it had much less blow out, but I did loose about 5-6 mph's on top. I am also kicking around the idea of putting on a jack-plate. Dealer said this would help out also. One last note, my motor was mounted lower than the dealer thought it should be with that motor/boat combo.

Good luck

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The nice thing about the hustler props are that you don't have to get a whole new hub and prop. You can get a hustler stainless prop housing and take the hub off your alum. one and use it on the stainless. That will at least help you save some coin if you are interested in switching to stainless. I know the perfomance would be better but I like the alum. so that if I hit something hopeful the prop breaks and nothing else. The hustlers are some of the best I have been told for being able to hit something and not do as much damage to the other parts.

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Quote:

does a question like this belong in this forum now?


This is the place for all boat / motor related questions now!

marine_man

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Something I'd definitely do when fishing lakes "up north"....switch to the alum. prop. Down here, lakes are mostly mud/sand/gravel with a some sparse rocks on points, so I'd probably use a ss prop down here. That's what I did with my previous Warrior...use alum. prop up north and ss prop around here. It's pretty easy swapping props around.

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This is now the "one stop shop" for all the good, the bad, and the ugly when it comes to boats and motors, eh? smirk.gif Sounds good!

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Yes that;s correct:

the good, the bad, and the ugly:

Valv, Marine_Man, and Kevin Turner.... wink.gif

..I am going to get in big troubles for this....ouch, ouch wink.gif

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Quote:

Yes that;s correct:

the good, the bad, and the ugly:

Valv, Marine_Man, and Kevin Turner....
wink.gif


Well, being bad is probably better than being ugly, right?

marine_man

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You are so nice Marine_Man, I was expecting to be beaten up pretty bad, I had this one coming.

I suppose being a grandpa helps a little doesn't it wink.gif

I am still under KT wrath, he hasn't seen this.... grin.gif

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Switch to a SS prop. I have a 17 mr pike with a 130 yamaha that came with an aluminum prop. With the aluminum prop the motor could only be tilted up 3/4 of the way (on trim gauge) and would sometimes lose its bite when a bigger wave comes. I put on a stainless Rapture 3-blade prop, now I can tilt the motor up past the point where the tilt kicks in and the prop shoots a big rooster tail. The stainless props have a much better and more aggresive design. I noticed it really lifted the transom of the boat up when on plane, especially when at WOT. For best performance go with stainless.

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If you are up past the trim limit and into the tilt and getting a big rooster tail, you are losing peformance and well past the best position for the motor to run efficiently. The highest you should get for a rooster is level with the top of the motor cowling.

A very common misconception with trimming the motor is relying soley on the gauge itself. Trimming a motor is always variable depending on the conditions you are in. Flat out straight you can trim up to the point the motor starts to gain RPM due to slipping and not gain speed or the boat starts to porpoise. Any further and you are only wasting gas and throwing water. Trim it down just a touch from there and you are as efficeint as you can get (at speed).

IMHO, with the hustler prop, you are giving up a bunch in performance due to the prop. From what I know of that particular brand, it is not going to do very well for most set-ups who want speed and handling (as most stock OE aluminum props are). My suggestion: Get a good stainless and leave the motor height alone until you test it there. I'll bet you can either leave it alone or potentially raise the motor a hole or two. I would suggest watching hsolist a bit for a Yamaha Pro series or possibly a Michigan Ballistic. With either of these props, you may need to drop an inch or so in pitch to keep your RPMs up, but if you are able to raise the motor up a bolt hole, you'll gain some of that back. Any motor over 100hp will benefit from a stainless prop since it does not flex anywhere near as much as an aluminum prop. You will find the money for a good stainless will not be a wasted effort..you'll be grinning from ear to ear.

Most aluminum v-hull boats will allow you to run the motor in the highest position with a good high rake stainless prop. I have added a 4" setback to my boat to raise the motor even more than that (in going this route, I made sure to have a water pressure gauge installed since I would be going beyond the mounting limits of the motor...which would not require a pressure gauge).

With enough seat time and a few different props to test, you will find a prop that is both fast and grabs well, allowing you to just "float" along at cruise speed. The most efficient set-up will really free up the handling of the boat with little trimming down for turning.

Steve

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Quote:

If you are up past the trim limit and into the tilt and getting a big rooster tail, you are losing peformance and well past the best position for the motor to run efficiently. The highest you should get for a rooster is level with the top of the motor cowling.

A very common misconception with trimming the motor is relying soley on the gauge itself. Trimming a motor is always variable depending on the conditions you are in. Flat out straight you can trim up to the point the motor starts to gain RPM due to slipping and not gain speed or the boat starts to porpoise. Any further and you are only wasting gas and throwing water. Trim it down just a touch from there and you are as efficeint as you can get (at speed).

IMHO, with the hustler prop, you are giving up a bunch in performance due to the prop. From what I know of that particular brand, it is not going to do very well for most set-ups who want speed and handling (as most stock OE aluminum props are). My suggestion: Get a good stainless and leave the motor height alone until you test it there. I'll bet you can either leave it alone or potentially raise the motor a hole or two. I would suggest watching
hsolist
a bit for a Yamaha Pro series or possibly a Michigan Ballistic. With either of these props, you may need to drop an inch or so in pitch to keep your RPMs up, but if you are able to raise the motor up a bolt hole, you'll gain some of that back. Any motor over 100hp will benefit from a stainless prop since it does not flex anywhere near as much as an aluminum prop. You will find the money for a good stainless will not be a wasted effort..you'll be grinning from ear to ear.

Steve


Yeah, I know once the motor trim gets over certain point the speed drops off, thats not my point. The point is the prop keeps the bite on the water and does not unload and rev the motor like an aluminum prop may due. IMO it is important to take a GPS and experiment with trim levels and comparing speed to rpm and where the speed drops off when trimmed too high. Every trim gauge is a little different and for me is just a reference point where the motor is without looking back.

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One quick check for motor height, is while boat is on the trailer, trim motor all the way down ( be sure front of trailer is down as to not lift the back up with the skeg). The cavitation plate on the motor should be on the same plane as the bottom of the keel or very close. If it is higher, say an inch or more than it is quite possible that is your problem. Al though a ss prop will provide better over all performance, an aluminum prop should still " hold" while the motor is tucked all the way in. I have personally ran many boats with much more HP and have found this to be be the case. Also did you buy this from a dealer new or used? if that is the case I would think they would be able to be able to work with you on this issue.

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