TE 31 Prop Reconditioning

[kowal_53]

TE 31 Prop Reconditioning

I have a new to me 2008 TE 31. The boat is getting it winter work over. During the sea trial the Cummins man recommended that I re-prop the boat to gain an extra 100 rpm.

Cummins QSC 8.3 500 HP
ZF Marine 1.76 to 1 Reduction
2-inch shaft
4 bladed 24 x 27 Prop

Full Load wide open was 2520 RPM, 80 RPM below the rated 2600 RPM for 500 HP in the specification manual. (21.1 Knots)

No load wide-open test was 2650 RPM.

The Cumming’s man said to re-prop to get another 100 RPM at full throttle to be at spec. Am I shooting for 2750 no load, or 2620 under load?

Given what I have heard I would have guessed 100 rpm above 2600 under load.

The last time I did this was on my 28. I took the prop into the prop shop. They look up the boat, engine, and decided what I needed. I could do this this time, but it seems that there might be an issue doing it this way.

Is there a recommended methodology to verify what I am supposed to have here?

[jleonard]

You re pitch a prop to change your under load rpm.
To change your no load rpm you need to adjust the injection pump. (You probably want a mechanic to do this)

[RobS]

Quantum series will not see the ++++ no load due to the electronic controls.

If the 2,520 was truly fully loaded you may get away with dropping an inch of pitch but 1.5 to 2" may actually be needed.

[Pitou]

TE 31 Prop Reconditioning

I have a new to me 2008 TE 31. The boat is getting it winter work over. During the sea trial the Cummins man recommended that I re-prop the boat to gain an extra 100 rpm.

Cummins QSC 8.3 500 HP
ZF Marine 1.76 to 1 Reduction
2-inch shaft
4 bladed 24 x 27 Prop

Full Load wide open was 2520 RPM, 80 RPM below the rated 2600 RPM for 500 HP in the specification manual. (21.1 Knots)

No load wide-open test was 2650 RPM.

The Cumming’s man said to re-prop to get another 100 RPM at full throttle to be at spec. Am I shooting for 2750 no load, or 2620 under load?

Given what I have heard I would have guessed 100 rpm above 2600 under load.

The last time I did this was on my 28. I took the prop into the prop shop. They look up the boat, engine, and decided what I needed. I could do this this time, but it seems that there might be an issue doing it this way.

Is there a recommended methodology to verify what I am supposed to have here?

Rob is correct on the "Q" series not getting the +++ that many of us are used to with the mechanicals.

My new to me has the same engine and engine, gear, shaft and 4 blade prop. Only difference the prop is 24 X 24.
Loaded I get 2640 and 21 kts.

Your boat may be loaded differently making your pitch requirement slightly different. I'd drop the pitch 1 to 1 1/2 inches to start and as Rob stated 2 might prove necessary as gear comes aboard. It's not always easy to nail this down on the first try.

[Carl]

I used these people to tune my prop and they nailed it first time. They are just across the bridge from you if you do not already have someone to do it. They will ask you many questions about your boat and needs, and are very professional. The hardest part was getting the prop off!


http://www.blackdogprops.com/

[RobS]

With the electronic engine the way to look at your propping is to compare actual fuel burn to the printed fuel curve. The only place you should be "off the chart" is when she is getting over the hump. Otherwise, actual burn should be close to the printed spec or you are overloaded. If I remember correctly, oddly your boat was setup without the smart craft display usual to the quantum series so unfortunately, unless you have a floscan, the fuel burn numbers won't be at your fingertips..

[kowal_53]

Just curious, what does ++++ refer to? I did read an article that claimed that 1 inch of pitch is equal to 200 rpm. (That would say I am 1/2 inch away)

Of course once the prop sees the computer we will find what I actually have, given wear and tear.

[RobS]

+++ refers to the rpms over your rated rpms