prop cavitation

Im having trouble with cavitation eating away at my props. The current prop only has about 20 hours on it, and has streaks where the paint has come off and you can see slight pitting in the aluminum. It has the exact same pattern on all blades so I know its not just paint coming off in one spot. What can I do to prevent this?

Boat is a maxum 2100SR with newer 5.7, pro is a powertech 14 1/2x19 3 blade aluminum prop. I have had 1 other powertech props do this on this boat, and then one Michigan that seemed to hold up fine. On another boat I used a powertech 2 years without problems. Is it possible the powertech blade design different enough to cause the problem with this boat. Any experience?

Re: prop cavitation

I seem to recall a similar powertech problem some months ago.
Not really sure you might try a power tech search and see what comes up.
what is the wot rpm and gps speed.
I can say I don't recall a cavitation problem with the Solas props or for that matter other props in general.
I have heard that cavitation scars can be an indication the prop is working very well.
I do have 4 11" and 12" merc brand props from a 65,50 hp Merc on a 18 ft Crestliner utility all have the same cavitation scars.
the oldest is quite severe the youngest has just dots starting with very low hours.
Are you saying the michigan had no scars or minimal scaring?

Re: prop cavitation

It IS the powertech design causing the problem. Replace with a Michigan Wheel propeller, problem solved.

Re: prop cavitation

WOT with full load 6 adults, couple kids and gear is about 4900, not trimmed. Don't have a GPS speed. Accelerates good from a stop even towing a slalom. Will stay on plane about 2400, typically cruise about 2800, rarely have a need to run 3500+ unless a short blast just for fun on calm water.


First powertech I had on another boat ran 2 years and looked brand new.

First prop on this boat was Michigan had no scars. Prop looked brand new after being on a whole season and spending the same week long trip in the Ozarks..

The first powertech on this boat was new then we spent a week in the Ozarks and when we pulled it out the paint was missing in strips through the middle of the blade. After installing a new engine this year we re-propped with another powertech and same thing. After a week in the Ozarks had a similar pattern through the middle of the blade, and also down near the root of the blade. That is when looking at the prop from behind the boat(thrust side). The first time around I thought it was just an odd combination of blade design and this boat. Seems odd why it keeps happening.

I don't know what to think at this point. On the surface seems somewhat tied to the powertech and this boat, but to be honest we never ran the Michigan with this engine either. Maybe its overpowering the prop now? Old engine was a weak 225HP 5.0, this is a 325HP 5.7, the old engine would cough and weeze pulling a skier up, this one will take all throttle you want to give and not hesitate even with boat loaded.

Re: prop cavitation

4900 with a boat load of people seems good but you need to be careful not to over rev with a light load.
Couldn't find info on that particular motor but I don't think it should exceed 5000.
It would seem that a 19 isn't enough prop for the 325 It seems it would probably run well over 5000 with a light load.
without a gps speed we can't tell how the prop is working.Some cells have a gps app.Some one of those 6 adults must have a gps of some sort.

Re: prop cavitation

This was a local built engine not a mercury or GM replacement, Blue-printed and machined to closer tolerances, balanced, etc. but using the same cam as stock with addition of 4 barrel carburetor. Basically a slightly better "stock" engine. Mercury recommendation for these is 4800, this engine valvetrain was built to handle 5500+ (just for a little safety margin) and was dynoed to 6000. It has a rev limiter so it wont go over about 4900 anyway.

It would run over 5000 rpm with a light load, even a full load and trimmed out would go over 5000 but we never have a need to run wide open like that. We went with 19 because we wanted better pulling power, and didn't care about going faster on top. After having valve issues with the old engine, I would rather prop to the very top or slightly past top of rpm range and pull back at WOT to not work the engine as hard all the time through the middle. Plus seems like the boats always seem to perform better slightly under-propped, at least to me.

We never GPS'd it, Im sure someone has access to it but we thought it was working well and didn't have a reason to question it until we pulled it out after a week of being in the lake. Boat speedo (I know not very accurate) showed 50 mph, My calcs at 15% slip come out to 51 so I think that seems reasonable.

I have contacted powertech and they are looking into it. Of course they said they hadn't heard of this problem, but I find that hard to believe as Im sure I am not the only one. When I know more ill pass it along.

Re: prop cavitation

I bought a volvo 4 blade 20p prop right here on iboats for my vintate 73' e-rude 135. Same thing happened the first time I used it paint peeled form the center of all 4 blades, probably less that an hour runtime. Iboats kindly told me, too bad - you used it no return/replacement.

Re: prop cavitation

The first prop I had this happen to the local prop shop took it back and swapped it for a new one, no questions asked. We never ran that second prop long enough t know if it would have done it again. Now that it happened again on a different prop I contacted powertech direct and should know tomorrow if what they decided about the cause, and whether they are going to swap it etc.

I looked at the prop again this weekend and it defineltlly looks like pitting so im guessing it is actually cavitation not just bad paint. I have also found some info that the powertech can be a little inconsistent from prop to prop and blade to blade so I may be prop shopping to try something else.

Re: prop cavitation

I have had excellent performance from two different props from Power Tech. I've talked directly to them a couple of times on each occasion and their expertise and service was first rate.

I would give them the data about the boat and let them select the right prop for the boat with your needs in mind. It sounds like there's an improper selection with your boat and this prop.

The last time they spec'd one for me was early this spring on a pontoon boat and then I found a few of their dealers to buy it from and ask them what to run on the same boat (before I told them I had a spec) and the info was all over the board. Most of the dealers handled other brands also. Based on this I'm not sure the average dealer knows how to get it right. In fact I'm sure most don't. I finally had to order the prop Power Tech spec'd against the advice of the dealer and it was perfect for the boat. These folks know what they're talking about and if you tell them what you have and what you want to do they can get it right and I think they have a return policy if it needs to be tweaked.

I'm guessing the manufacturer of the boat made the selection based on cost and average use. From what I understand about cavitation there is a tremendous vacuum on the back side of the blade causing the water bubbles to flash in a violent manor (kind of like popping the cap off a radiator when the car is hot). If this is happening, I can't see this being the right prop for this boat. Metal or aluminum can only stand so much.

It would not surprise me if they recommended one of their 4 blade props for this type of boat.