Prop for 31TE

[wpcv1776]

Hi Everyone. We just bought a 31TE with a single 450hp Cummins. The prop is a 24x24 4 blade. The engine will not hit it's max rpm of 2600. It tops out about 2500 -2550. I realize there could be a lot of potential reasons for this, but I suspect the boat is over propped. Anyone out there with the same engine and boat? I would love to know what prop you're using. I've seen the same configuration with a 24x22 4 blade, and since we are planning to run heavy a lot with dive gear etc. I'm thinking this is the way to go. Just looking for second opinions.

[Russell]

If the hull and prop are clean you are probably correct that you need to reduce the pitch. If you take it to a propeller shop they should be able to give you a good idea how much to take off although your suggestion to go down to 22 sounds about right. Most shops will also lend you a prop puller if you do not have one.

[Pitou]

I know that Joint Venture has a Cummins 6 CTA 8.3 M3 / 450 HP and is propped correctly with a 24 X 24, Medium Cup, 2 inch std. taper made by Hy Torq / probably 4 blade and I'm sure John reaches his proper loaded RPM.

I'd send him a PM for some help if you have that same engine.

[kowal_53]

I though tachs were known to be inaccurate. So do you have to go out a get a calibrated tach to check what the engine is actually doing? It seems like one should figure that out before asking the prop man to change your pitch.

Perhaps one should have the prop man check what is actually going on. It is conceivable that the prop just is not true as it should, something one might expect over time.

Perhaps we have an expert that might ahead some light on how to get to the bottom of this. I am sure you only want to take the prop in once.

[RobS]

Check high idle (no load) rpm and phototach the engine before messing with the prop.

[addon323]

Check high idle (no load) rpm and phototach the engine before messing with the prop.

I have a similar issue and was wondering what is the best way to phototach the engine. I also have the 450 Cummins engine. Has anyone done this before and if so, can you offer advice on the best way to do it. Thank you.

[Russell]

After watching the Cummins mechanic do it, I purchased an inexpensive phototach on eBay and it csme with a strip of reflective tape. You put a piece of the tape on the flywheel and every time it goes around it triggers the phototach.

[jointventure]

I have a 2001 31TE with a 8.3 450 Cummins, and a 24x24 slightly cupped 4 blade prop. With an average load and favorable tide and wind at 2600rpm the boat will approach 21 - 22kts

Personally I wouldn't mess with the prop , rather check bottom condition, boat load - fuel, water, holding tank, extra stuff that accumulates, and run it at slack tide and no wind.

[lawrento]

I have a 2001 31TE with a 8.3 450 Cummins, and a 24x24 slightly cupped 4 blade prop. With an average load and favorable tide and wind at 2600rpm the boat will approach 21 - 22kts

Personally I wouldn't mess with the prop , rather check bottom condition, boat load - fuel, water, holding tank, extra stuff that accumulates, and run it at slack tide and no wind.

Hi Jointventure and other 31TEOwners with 450 Cummins and 24x24x4blade prop.
Wish to know what's your prop shaft diameter and transmission gear ratio ?
My 31TE is using a 1.75" shaft and a ZF transmission 1.76:1 ratio .
Also what's the weight of your 24x24x4blade propeller ?
I'm also considering to change my current prop of 22x25 to this size 24x24.
Thanks !
Lawrento
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