Need help choosing correct propeller??

[blg2007]

I have a 1997 Caravelle S1900 Bowrider
Its 19ft in length
Approx Net Weight is 2400lbs
Average load( with driver, passengers,fluids, and gear) is 3200lbs.
Bottom is in great condition, fresh wax.

It has 3.0L Volvo Penta GS
SX Cobra Outdrive (19 spline thru-hub exhaust)
4 3/4 gearcase 1.97 gear ratio
RPM range 4200-4600
Current prop is a Aluminum 3 blade 17 pitch.
Engine has a fresh tune up, throttle is opening all the way.

I have only owned the boat for a month, I've had it on the water twice and I have been very dissapointed with the results. The boat has a terrible hole shot, takes a while to plane, has a very low top speed (20-25mph) and I'm having trouble getting it in the rpm range, will only get 4200rpms fully trimmed out (bow up) this is with average load.

The prop has a lot of damage, all blades have severe pitting. My guess is that the previous owner has struck an object(s) with this aluminum prop. If so is it possible that this has caused the prop pitch to get out of pitch? Would this more than likely be my problem? I also have a lot of cavitation when I'm trimmed out (you can see water spraying up from prop).

We do a lot of tubing, skiing, wakeboarding (adults).

I'm considering getting a 3 blade 19 pitch aluminum prop. This should increase my top speed.

Do you think this will be a good prop for my boat, boating style? What would you recommend me going with? Should I try a 4-blade? Recommend a brand?
Thanks in Advance.

 

[blg2007]

Re: Need help choosing correct propeller??

bump

 

[hwsiii]

Re: Need help choosing correct propeller??

Blg, something is wrong, that 17" prop ought to make that boat jump onto a plane with a 1.97 to 1 gear ratio and it ought to over rev that engine a lot. Try to borrow another prop and try that, I show you need a higher pitch than you are running. And I believe that prop is slowing you down tremendously and hurting your outdrive bearings, unless you have a motor problem.

H

 

[blg2007]

Re: Need help choosing correct propeller??

Blg, something is wrong, that 17" prop ought to make that boat jump onto a plane with a 1.97 to 1 gear ratio and it ought to over rev that engine a lot. Try to borrow another prop and try that, I show you need a higher pitch than you are running. And I believe that prop is slowing you down tremendously and hurting your outdrive bearings, unless you have a motor problem.

H

Thanks for the reply hwsiii, I also thought that the boat should launch out of the hole with this prop. But I believe my problem is the prop itself. It has severe damage. Could this be causing my problem? I've attached some pictures. The boat only has 75 hours on it.

 

[hwsiii]

Re: Need help choosing correct propeller??

I can't tell good from the pictures but either that prop has a real problem, or your motor has a problem. The prop looks real bad, but I can't see it bent or anything, although those leading edges could be bad enough to disrupt the water flow a lot and that would keep the RPM down and make getting on plane very slow that cavitation or ventilation you are seeing behind the boat is a good indication that prop is not good anymore. try to borrow a prop that is between 17" and 20" Pitch aluminum and run a trial test with it and get back with me on the WOT RPM and the speed, and we will figure this out.

H

 

[blg2007]

Re: Need help choosing correct propeller??

I can't tell good from the pictures but either that prop has a real problem, or your motor has a problem. The prop looks real bad, but I can't see it bent or anything, although those leading edges could be bad enough to disrupt the water flow a lot and that would keep the RPM down and make getting on plane very slow that cavitation or ventilation you are seeing behind the boat is a good indication that prop is not good anymore. try to borrow a prop that is between 17" and 20" Pitch aluminum and run a trial test with it and get back with me on the WOT RPM and the speed, and we will figure this out.

H

Okay I'll see if I can find one. Thanks

 

[MikDee]

Re: Need help choosing correct propeller??

I would guess top speed should be close to 40 with a 19" pitch prop on your boat, it sounds like the hub in your prop is shot,& slipping, this could happen by hitting something while under power, especially looking at that prop, I would suspect that.

 

[hwsiii]

Re: Need help choosing correct propeller??

Mik, the only reason I didn't think that was the problem is because he can't turn but 4,200 RPM at WOT. If it was slipping he should turn a lotttt more RPM.

H

 

[MikDee]

Re: Need help choosing correct propeller??

Mik, the only reason I didn't think that was the problem is because he can't turn but 4,200 RPM at WOT. If it was slipping he should turn a lotttt more RPM.

H

Yes, but he's only doing about 20-25mph @4200rpm His engine maybe a bit sick also. Either way, he needs to beg, borrow, or steal, another prop to try.

 

[hwsiii]

Re: Need help choosing correct propeller??

I certainly agree he needs to try another prop, to see if it is the motor or the prop. My program shows you should be doing at least 36 MPH. We can discuss the 4 blade after we find out what it does with a good prop, because your prop slip number right now is at 27%, even at 25 MPH. Although I do believe a 4 blade is what you need to lower the prop slip i think you are going to have.

H

 

[redone4x4]

Re: Need help choosing correct propeller??

4200 rpms being the highest wouldnt bother me, the slow speed at that rpm would. i dont ever run over 4000 rpms on mine, but it does at least 30 with a 19 pitch prop on it.

 

[blg2007]

Re: Need help choosing correct propeller??

I could not find anyone around here with a 19 spline prop laying around so I went ahead and ordered one off of iboats (19 pitch 3-blade aluminum QL by Volvo Penta),should be here wednesday, made sure to get one with an interchangable hub just in case the prop doesn't help me and I need to get rid of it. The motor seems to run like a top. The carb was just re-built, complete tune-up. I'm having the sea water pump replaced tomorrow, going to have them check the timing on it as well just in case. Talked to a local Volvo Penta dealer and they said only 4200 rpms was not too bad.

Update on prop: If looking from the top at one of the blades it seems to be in a slight S shape, I would guess this is not good for speed or the drive bearings for that matter.

 

[blg2007]

Re: Need help choosing correct propeller??

I just thought I would update this question for anyone who may have similar problems.

UPDATE:
Checked the timing, it was 8 degrees out at TDC. Major Issue. Fixed timing, installed 19 pitch prop. It was running high 30's at 4300 rpms. Much Better!