Tolly needs a Prop

[Coopthing]

I Have a repowered 1974 26 foot Tollycraft. 454 340HP. Borg and Warner 1:1 Velvet drive, straight shaft. 24 ft at the water line. 9000 lbs. Has anyone had this configuration and have any prop suggestions. Currently has a Nibral 3 blade 14x8 cupped. It's not doing the trick. 17 knots top speed. Had a 15x9 3 blade on it, prop was loading up and not reaching peak RPM of 4400. Seems ridiculous to have that much power and not be able to cruise on step.

 

[Bondo]

I Have a repowered 1974 26 foot Tollycraft. 454 340HP. Borg and Warner 1:1 Velvet drive, straight shaft. 24 ft at the water line. 9000 lbs. Has anyone had this configuration and have any prop suggestions. Currently has a Nibral 3 blade 14x8 cupped. It's not doing the trick. 17 knots top speed. Had a 15x9 3 blade on it, prop was loading up and not reaching peak RPM of 4400. Seems ridiculous to have that much power and not be able to cruise on step.

Ayuh,...... Welcome Aboard,..... Is it a Planin' hull, or Displacement hull,..??

Displacement hulls never run "on plane",....

 

[Coopthing]

Thanks for the question. Yes, it is a planin hull. Some folks with these boats, 350 V drives, 2:1 and 19X18 props are achieving upwards of 30 knots. I don't need to go that fast but I am looking at fuel burned for distance traveled. I have been to a few prop shops. Prop calculator says 13x9 to achieve 27 knots. I'm not that far off now whit 14X8 and if I understand correctly 1 inch of diameter is equal to 2 degrees of pitch. Was just hoping to find someone with similar equipment and experience and can take the guess work out of it.

Last boat: 1954 36' Monk Trawler

 

[steelespike]

I really can't be too specific but usually a 9000 lb. boat would require a lot of diameter.
A 14" diameter is something you would find on say a 3.a I/O runabout 2.00 ratio and about 19" pitch.
I had a antique 4000 lb runabout with a 125 hp @ 3200 rpm Lycoming straight 8,It had a little too big 14 X 14 prop
It would turn about 2900 at about 30 mph.Apples and oranges but::
I would think your 340 hp should manage ay least a 16" diameter with less pitch than the V drives.
In my opinion the 8" pitch should be screaming.Lots of rpm but not much speed. I think something is wrong with your motor/setup.
Don't assume everything is right just because its a new install.
Is the motor new?

 

[Coopthing]

Thanks for your thoughts. The motor is a complete on the bench rebuild. No complaints about the way it runs. I did have a heat issue on the port side but found they put the wrong gasket on the starboard exhaust elbow. The engine is still going through break in. 26 Tollycrafts were built in the early years with a full keel and with the straight shaft there is not much room to swing a big prop. The 15 X 9 prop was giving me 4100 RPM and 17 knots full out. The harmonic vibration through the hull was unbearable. I checked the throttle cable to assure I was getting a full throw on the carb, also new and set up correctly. The prop shop suggested cutting it down to 14X8 with #3 cup. The harmonics through the hull changed and sounds normal. I get 13 knots at 3600. Don't know what top end is yet or what it's like coming out of the hole because it is still in the early stages of break in. This hurts my brain, lol. Is there not a magic prop genie out there, a prop guru who can definitively send me to the prop mecca super store for the correct prop for my boat and tell me to stop whining about fuel consumption. "IT'S A 454"

 

[Coopthing]

Sooo. I had the boat out this weekend. I opened her up to 4400 rpm and topped out at 14 knots. I had more throttle left. How much, I don't know as I don't want to over rev the engine. I went to the Tollycraft Rendezvous and had a chance to talk to other tolly owners. Unfortunatly, no one could solve this dilemma. Most boat like mine are running V drives with 2:1 gears and 19 inch props. They are getting 20 to 25 knots out of 350s. Am I thinking properly when I think that if an inch of diameter is equal to 2 degrees of pitch, so they have four inches which would equal 8 degrees of pitch and I think that should put me at 14x16.

 

[Coopthing]

Something I have found about forums is that once someone has resolved the issue, they seldom post how it was resolved. I was in contact with someone who had the same boat, same year and same engine drive configuration. He had the same issues. The final solution was 14x12 3 blade with max cup. He was satisfied with the performance and economy, if there is such a thing with a 454 crusader. However. I will try this combo and post the results. Thank you to those who responded. Michigan Wheel responded to my inquirers and suggested to pitch up to 9 and cup.

 

[Coopthing]

All is good now. 24.3 knots at 4100 WOT is 4400 as it should be. It was pretty snotty and wind out there when I took her out for a test. I think she'll do 26 on a flat sea. 18 knots cruise at 3400RPM final prop 14X12 Cupped. an inch and a half clearance on the prop. Not buzzy or unbearable harmonics. This has made me very happy. Thanks to all who have tried to help. Happy boating. Oh and if your velvet drive goes crunch crunch thump, check for a plug wire off or a dead cylinder.