Prop question

[33youngbrothers]

When I bought my boat it had a bronze 22x24 prop with a cage. Removed the cage and instead of reconditioning the prop I bought a nibral 22x25 off eBay. This props blades are huge and almost overlap eachother. I was very happy with that cruise but id heat up to about 195(mechanic says 190 or lower). So I repitched to 22x23 and instantly noticed a slower cruise but my heat is good. Anyone have any thoughts on what prop I should have? My buddy's got the same hull with a 3116 cat and he's running a 22 square.

Found a 22x25 bronze with more traditional blades that I've been thinking of trying.
33' yb
220 jd w/ keel pipes
2-1 twin disk

 

[33youngbrothers]

Nibral wheel

 

[MDI45]

What's top end on that motor?what RPM did you hit with the 22x25 and RPM now?

 

[33youngbrothers]

what's top end on that motor?what rpm did you hit with the 22x25 and rpm now?

2650.

2550

2550

 

[MDI45]

I would have a inch of pitch taken off the 22x25......you should pick up a 100 rpm

 

[blackdiamond296]

2650.

2550

2550

Something doesn't make sense here- you took 2" of pitch out of the 22x25 and still hit the same 2550 on the top?

 

[Brooksie]

Something doesn't make sense here- you took 2" of pitch out of the 22x25 and still hit the same 2550 on the top?

Check your tach b/4 you start cut & try. If you reduced pitch and still turned same RPM sounds like the governor may be out of wack. But zero in your tach first.

 

[captainlarry84]

When I bought my boat it had a bronze 22x24 prop with a cage. Removed the cage and instead of reconditioning the prop I bought a nibral 22x25 off eBay. This props blades are huge and almost overlap eachother. I was very happy with that cruise but id heat up to about 195(mechanic says 190 or lower). So I repitched to 22x23 and instantly noticed a slower cruise but my heat is good. Anyone have any thoughts on what prop I should have? My buddy's got the same hull with a 3116 cat and he's running a 22 square.

Found a 22x25 bronze with more traditional blades that I've been thinking of trying.
33' yb
220 jd w/ keel pipes
2-1 twin disk

You purchased an E Bay propeller. Do you have the history on the wheel? If the blades look that odd it is possible that you purchased a cut down wheel. Cut wheels never work as well a full design wheels. Do you know what the original pitch was also? Taking 2" out of a Nibral is a lot of bending. I think it best that you start with a fresh wheel.

RE-cap you are looking to wheel a 220 HP John Deer & 2650 RPMs with a 2:1 gear & a keel cooler is this correct before we start our math?

 

[33youngbrothers]

RE-cap you are looking to wheel a 220 HP John Deer & 2650 RPMs with a 2:1 gear & a keel cooler is this correct before we start our math?

That is correct

 

[captainlarry84]

That is correct

I did my math several times. for a 220 HP JD @ 2650 with a 2:0 gear the wheel comes out to a 22 X 18 or a 21 X 19. Plus I gave no consideration to the keel tubes. Your original #s with the 22 X 25 to a 22 X 23 do not ad up. I would recommend that you stop looking a used wheels which may have been cut & re-pitched more that you can image & bite the bullet, go to a local propeller shop and get it correct the 1st time. Your 22 X 25 will make a fine lawn ornament in the spring.
There is also no need for you to buy Nibral. A bronze at 1/2 the price is all you need with your current power combo.
Lastly if your temp creep up with the over-wheeling it is a sign that you may need to clean out your cooling system. A diesel engine that is over wheel should only loss RPMs & not gain temperature, unless the overload in gross.

As for your buddies boat if he has the same rig as you with a 3116 @ 350 HP his correct wheel would be the 22 X 22. But be is in a different class that you by over 100 HP.

 

[Brooksie]

Larry, Your numbers are always great so I hesitate to interject but here goes.

My 35 Bruno with only 150hp 1.9:1 carries a 22 X 18 4 blade and turns 2450 clean. It seems that this smaller vessel, with 50% more HP, and 5% more reduction, could handle a larger prop than 22 x 18.

By the way, I still think his tach is wrong & he is up against the governor w/ both his props and that is why the rpm didn't change when he changed pitch.

 

[lobstercatcher]

I would have a inch of pitch taken off the 22x25......you should pick up a 100 rpm

I'm in this camp. No way would I go any less than this based on what you are saying. Make sure you have a clean bottom, clean keel coolers and the thermostat is working correctly along with , as suggested the tac is reading correctly. If you go with a new wheel I would go with 22x 24 and you may have to bump back up to 22x25 if everything is clean. Are you getting a ton of hours on the engine that you may want to bring down strain on the engine to extend life? That would be the only reason to going under 24 pitch imo.

 

[captainlarry84]

Larry, Your numbers are always great so I hesitate to interject but here goes.

My 35 Bruno with only 150hp 1.9:1 carries a 22 X 18 4 blade and turns 2450 clean. It seems that this smaller vessel, with 50% more HP, and 5% more reduction, could handle a larger prop than 22 x 18.

By the way, I still think his tach is wrong & he is up against the governor w/ both his peops and that is why the rpm didn't change when he changed pitch.

Interesting on your wheel size. Your WOT RPMs are 200 less which is a lot, then again you are also down 70 HP?? You are swing a lot of wheel for a 150 HP. Keep that motor!

 

[Brooksie]

Interesting on your wheel size. Your WOT RPMs are 200 less which is a lot, then again you are also down 70 HP?? You are swing a lot of wheel for a 150 HP. Keep that motor!

I turn 1283 at the prop (2450/1.91) vs: his 1275 (2550/2) no difference really. Or if he turns 2650, 2650/2= 1325; still really no difference really 42 turns.

For $35. at Harbor Freight, he can get an optical tach and check his main tach and while he is at it his shaft speed. If his tach runs off his alternator, as most do, every time you change your belt it slightly changes your tach.
My theory is still that he is up against the governor, his tach is wrong, and he is shooting blind.