HELP with Props

[JC]

Hello Guys. Hope you are all doing well.

I am currently in the following situation. Just finished boat remodel put in a small bathroom and fiberglassed the front plus a bunch of other stuff. My current problem is with propellers. Our boat has a full tuna tower, cummins 250HP 6bta Engines, no Generator nor AC. Normally fish 6-7 people (250 galon fuel tank).

We are currently overproped. Did test and are only reaching 2400 and should reach 2600-2625.

My current props are 4 blade HyTorq 21" diameter, 22" pitch and #6 cup ( i believe this is a medium cup).

Anyone with recomendations to try and find the right pitch and cup? Its difficult for me because in Central America so we can be doing trial and error... rather be conservative than overly aggressive.

Thanks for your input.
JC

[Carl]

Remove minimum One Inch of pitch. Two would be better.

One inch less should give you 2600

Two inches less should put you at 2800


If your guy does half inch you could squeak into the middle, it would be my first choice...but many do not have the pitchometer gauges for that.


I too am a fan of running conservative.
If I had to make a one time choice that I'd have to live with, it would be remove 2" of pitch.
But if I could go back and tweak again, if not quite where I wanted to be, I'd loose 1" of pitch and go down 1 or 2 on the cup.
That is unless they did the 1/2" changes, I'd jump on 1-1/2".

Or go 3 blade...thats also a 200rpm gain.

With all my back and forth...I'd rely on a good prop guys expertise after he has seen the wheels and given all the info. Not always possible...

While I am a fan of running conservative, I'm not a fan of "big" prop moves.

[Tony Meola]

Carls right. You need to square your wheels off a little more.

You are running pretty heavy. Most of us are only carrying 220 to 230 gallons of fuel. Some lighter.

Diesel fuel weighs a little more than 7 lbs per gallon. So you are already carrying 210 pounds more than most of us and it is all in the stern. Then you add in the tower that adds weight plus wind resistance. 6 to 7 people is heavy most are probably 4 to 5 people so there is another 400 lbs.

Not sure how well it works but if you join BoatDiesel.com you can give their prop calculater a try. You will need the weight of the boat to use the calculator.

Cruise would be around 2200 to 2300 RPMs and you should be around 23 to 24 knots.

Since it sounds like you do not have any real good prop shops around you, how do you get your props? If you are dealing with a US prop shop and having the props mailed to you, then give the US shop a call and talk to them.

[JC]

Thanks Carl and Tony for your good replys. I have written a request to Lauderdale Props in Florida to see what they suggest but I think I will do as you say and better call and explain. The boat is definetly overpropped... i knew immediately when we hit 2200 rpms and were doing 24 knots. My target is to cruiste at 2300 rpms at 23 knots or 2400 24 knots when under a hurry (tournament time) but knowing we can reach our target rpms with no problem. We are outside the safe operating curve right now.. Keep you guys posted to see what result I achieve. Thanks for your help. Its difficult because once I make my decision and props made i have to ship them down here and it is expensive to be shipping back for adjustments.....

Thanks
JC

[Carl]

i have to ship them down here and it is expensive to be shipping back for adjustments.....

Thanks
JC

I bet it is very expensive to be shipping heavy props back and forth...never mind the time it takes.

But your right in that it pays to ship props at a great expence then replace motors.

Glad you decided to talk to the Prop shop, they are the experts I'm rule of thumb.

Best of luck to you!

[JC]

OK. I paid for my new set today. Went with 4 blades Nibral 21" x 21" and a #3 cup instead of #6. Will let you know once they arrive here and we seatrial how well we all guessed.

I hope we guessed right. Nobody wanted to commit without an accurate weight so I kind of just went will all comments and gut feeling.

Take care.
JC

[Carl]

JC,

It doesn't help much, but that is right about exactly what I'd have done in your position.




Anybody in for a high low?

I'm in at 2700-2750 WOT with the new wheels.

[JC]

I really hope I didnt overdue it with going down both on pitch an cup. I need to go up to about 2650 max. Will see.... Engines rated to 2600RPMS...

JC

[Carl]

JC,

If your going to overdue...you went in the right direction.
Better to have a few RPM in the bank then be short.

[Tony Meola]

JC

Best place to be is square. I am running the 270 Cummins. Basically the same engine, different fuel pump, hence 20 more HP. I am running 4 blade 20x23 with about 3 cup. I turn up to 2650RPMS.

4 Blade is better for a heavy boat, it will bite in better and get the boat moving. You loose on the top end but up your cruise.

Now with that being said, there are and were members with the same engines as you turning 21 inch 4 Blade props.

I think you are going to be really close.

Let us know.

[EarleyBird]

I to also have the 270 Cummins. Been running 20X22 4 Blade Hy-Torque with #7 cup. All rpm’s are correct 2600 max. In addition have purchase a set of DQX wheels. Maximum Rpm’s stay the same, although the top end cruise speed rpm’s 2350-2400 give the boat a1973 Flybridge an addition knot or so. 4400hours on the motors. EarleyBird

[JC]

Thanks Tony. You dont have a tower on your boat? Interested in knowing what your cruise speed is with a 23 pitch. You must be light in order to reach 2600 with that pitch?

EarlyBird. Same question. What is your cruise speed ? You did find the DQX performance to be bettere? What were you running before? Dynaquad?

Thanks for the input.

JC

[EarleyBird]

I’ll try to answer your question with a couple facts based my Boat. I have a 1973 Flybridge with 270 Cummins. Original 220gallon fuel tank. Last Saturday left midnight for the 100 fathom line, 90 miles. Full tank of fuel, 4 grown men, 6 totes of ice in my port side cabin fishbox. One in the V-berth napping, one on the cushioned port side fishbox doing the same. Two men on the bridge on my aluminum cushion bench seat. 2000 rpm’s we were doing 18 plus. Trolled from 0445 til noon. Started breezing up, running 2200 doing 21knots, 2 80# collared YFT one 30 LF.in fishbox. Flattened out with 15 togo pushed her up to 2350 she was doing 24 plus. After 90 each way there was still more than 1/4 reading on the fuel gage,short trip, wasn’t going get my ass kicked. I say there was 80 left at the dock. Normally loaded 2000 rpm’s she does 20, 2200 she’s doing 22, just shy of 2400 she’s doing 24 plus. Take 100 out of her after an overnighter on the way home just shy of 2400 she’ll do 26 plus. Engines went in boat 2002, 4400 hours. Hope this helps.
EarleyBird

[Tony Meola]

JC

I am running light, no tower, 220 gallons of fuel. My numbers are about the same as Early Bird give or take a half knot. Once you are propped right, weight does not seem to have a huge impact on these Cummins holding the speed on these boats. Of course if you go over the top weight wise it will be a little harder to get her to plane off but once she does, for some reason weight doesn't bother her.

[EarleyBird]

Forgot...DQX Wheels at the higher RPM’s 2200-2600 my boat gets a knot faster. Like the old 4 blade Hy-Torqs for tuna Trolling. Speed DQX. Going fishing!
EarleyBird

[JC]

Thanks for your helpfull answers. I agree my goal is to have one knot for every 100RPM increase after 2000. The boat really doesnt like the 1500-1800 rpms range.... thats when the engines area really working to bring it out of the hole... Ill let you know how we do. Props shiping out of Miami next wednesday to El Salvador. Should have them on in 2 weeks time hopefully...

Nice Tunas Earlybird !! we lost a 150lb tuna 2 weeks ago after 40 minute fight on standup 50. It was about 25 feet under the boat. Bummer. We did release two marlin that day and cought two nice bull mahi though..

JC

[JC]

UPDATE

I got the props and are now on the boat.

PROPS are 21" x 21" with #3 cup. Michigan Wheel HyTorq MY-T4 NIBRAL

I could not fully test but the initial tests are very encouraging. I had decided to acid wash the heat exchangers that same day before sea trial once I went up on revs i was leaking water from two of the lids of heat exchanger... l already solved that issue but it affected me on test day.

But regarding the test I only had 3 guys onboard against 7 regularly for fishing minus ice and drinks. Full tank of fuel.

The boat came straight up on plane with no hesitation in the 1500-1800 rpms range and when throttles pushed it reacted immediately and rpms up to 2650 and i throttled down due to previous issues. It just feels so much more reactive and props slice thru water ver easily. I think once i have everyone onboard we will hit our target RPMS of 2600. Thanks for all your help. I have a tournament in 15 days aprox so will give the final veridict after when running with full gear and people.

JC

[Carl]

Thanks for update.
Good luck in the tournament and hope you hit your target with the props.
It would be awesome if you dialed them in perfectly on the first shot.
Let us know.

[Tony Meola]

JC

Good to hear. Hopefully you got it first shot. Square usually gets you real close on these boats.