Prop Suggestion

[bobbysky]

I dinged up my prop last night, went to my local prop shop to get a replacement and he gave me the completely wrong size. He gave me an acme 13.5 x 17.5. No power, with a top end of about 35mph @ 2400rpms. Plus there is a weird whistling noise when I put it in gear forward, and stays there until I give it gas.

I checked the shaft alignment and struts everything seems good. The dinged up prop wasn't that bad.

Suggestions for new prop? And the whistling noise?

Specs-

2002 23v

• 1.1 gear ratio
• 13x13 oj 4 blade prop was on there (don't know if it was stock
• around 2000lbs of ballast and people, sometimes more
• 2000ft elevation

)

I just want to get a little better hole shot when I'm loaded down, the 13x13 seemed to be fine, even when we had over 2800lbs of weight, just a little sluggish.

[chpthril]

If I'm reading my x-ref info correctly, the ACME replacement for the OJ 13x13 is the 579 13x12.125

If you want and improvement over a direct replacement, call ACME and get their suggestion.

[SPBFAN]

Give me a call. I have all the specs and contacts for this. I can help you get the prop and get it for the right price. If you go to ACME direct you will pay retail price. PM sent with phone number.

[talltigeguy]

I dinged up my prop last night, went to my local prop shop to get a replacement and he gave me the completely wrong size. He gave me an acme 13.5 x 17.5. No power, with a top end of about 35mph @ 2400rpms. Plus there is a weird whistling noise when I put it in gear forward, and stays there until I give it gas.

I checked the shaft alignment and struts everything seems good. The dinged up prop wasn't that bad.

Suggestions for new prop? And the whistling noise?

Specs-

2002 23v

• 1.1 gear ratio
• 13x13 oj 4 blade prop was on there (don't know if it was stock
• around 2000lbs of ballast and people, sometimes more
• 2000ft elevation

)

I just want to get a little better hole shot when I'm loaded down, the 13x13 seemed to be fine, even when we had over 2800lbs of weight, just a little sluggish.

What RPM?

Your cruising RPM is probably more likely supposed to be at 3k or more...maybe that is a typo, but 2400 usually isn't going to even get you on a good plane. I don't know how you would get 35MPH at that RPM.

[bobbysky]

okay guys I called acme and the recommended a couple of props.

Tall,
The rpms were that, it was just the completely wrong prop.

I'm going to try out a 4 blade 13x12.5 and see if that is going to work out. I will let you guys know the outcome.

[talltigeguy]

So if I am interpreting that right...the engine never could get up to speed with that unusual prop on there?

I would actually expect one of two things:

1. The boat has terrible hole shot, but the longer you stick to the throttle it eventually will get up to speed and in fact will actually have a faster top end.

2. The hole shot is incredible and you can't get over 30 MPH and the engine RPM's are way over the top.

Maybe someone smarter than me can expound here? I am not trying to doubt bobbysky's experience, but other than the RPM's being misread, I cannot explain it.


When I first got my boat, the RPM meter was off. There is a setting on it for different engines with a different number of cylinders. Mine was set wrong. I did not know any difference, so I never noticed, but my dealer did when he was on the water with me and fixed it. My wakeboarding RPM's were always around 2900-3000 depending on ballast.

Bobbysky, BTW, what is your usual wakeboarding RPM's for your boat?

[chpthril]

He went up in both dia and pitch, which would result in lower RPM. I'd guess that the increase in both, created enough extra bite, preventing the engine from even getting up to it's normal operating range.

[bobbysky]

I think Mike is right Tall.

I wasn't reading it incorrect. I read it both on the Perfect Pass GPS and my main RPM gauge. It was just way to much prop for my boat.

Normally when I'm wakeboarding, loaded down, I'm running just over 3000 RPMs

I tested out the new prop last night, and it worked great. WOT I was running around 4700 RPMs. At wakeboard speed I was sitting at 3100 RPMs. Plus I got a little more out of the hole then the original prop.

Thanks for the help guys.

[dogbert]

He went up in both dia and pitch, which would result in lower RPM. I'd guess that the increase in both, created enough extra bite, preventing the engine from even getting up to it's normal operating range.

That's what I would expect along with a lot of cavitation at the start, making it appear sluggish out of the hole. Think of it like trying to start from a stop in some other gear than 1st in a car (assuming a manual transmission). As you near the top end, it's kinda like climbing a hill that gets steeper and steeper. At some point, the gear ratio doesn't work for you and you have to drop down. All boats have a a maximum hull speed...no matter what kind of HP you throw at it, you're not going to go much faster than that.

[talltigeguy]

Good explanation.

I am just surprised that he could not get over 2400 RPM. I thought the boat once on plane would allow the prop to continue to accelerate. The most initial strain on the engine is lifting the boat out of the water from a dead start, no? It appears he just does not have enough power to get the RPM's up with that prop. If he could get his RPM's up to 4700, then he would go 60+MPH, right?

I can start my truck in 3rd gear...very sluggish, but once I get going, I can still max my RPM's. Not exactly a good comparison, but I still would expect a boat to still reach full RPM's...eventually, but I guess that larger prop pushes so much water that his engine could not do it.

[bobbysky]

I think cavitation plays a big roll in the problem. Just slipping through the water. I'm sure if I would have sat there wide open for a long time it may have gotten to that speed, but doubtful. It's amazing how a prop completely governs the engine.

I talked to my local Tige dealer, and he said that even on the new 400+hp boats with gear reduction, they wouldn't put that much pitch in the prop.