Propeller Change Thought

[carolynrose]

I'm researching for the purpose of a prop change. My OMC Stainless steel prop that was 15 x 15 repitched to 13 is now in need of replacement due to severe cavitation scoring. It worked well for a couple of years but now is done.

Boat specs are: 1988 Bayliner 2556 Convertible, 5.7 OMC, listed at 5300lbs dry when new. I added a flybridge enclosure and usually run with about 1/2 tank of fuel(50 gallons of fuel), and misc fishing gear and supplies, usually 3 people total on board.. Horsepower listed at 260 and WOT 4400.

My 15 x 13 3blade stainless prop served well until now. Hitting about 28 mph and WOT about 4300 with GPS and handheld tachometer.

Problem is no one actually makes this prop. I purchased and tested this prop and then had it repitched by a really good prop shop. I was hoping there was a good replacement since there are a lot of new props out now.

So I have been looking at Solas props. What do you think of a Solas HR Titan4 14.5 x 15 x 4 blade? The original props on these boats were 15.5 x 13 x 3 blade. I know the diameter is 1" less, but was thinking because it's a 4 blade it might work.

 

[jimmbo]

iboats list several, including 2 SS

http://boatpropellers.iboats.com/OMC...t_id=007532716

 

[carolynrose]

Yes there are several listed in the 15 1/2 x 13 size but some say they are bow lifting and some just say heavy boat. My last prop was from OMC and originally came 15 x 15. Reducing the diameter size and lowering the pitch allowed the engine to reach WOT spec. I am currently running my backup prop, like new condition, but it will not go over 24 mph and takes forever to get on plane. It is a Michigan match 15 1/2 x 13 x 3 blade. calculating the prop slip it is about 36%. My goal is to get a propeller that will help in Stern Lift. It seems that the 15 1/2 diameter does not work well on this boat. I have been researching and have read several articles that say reducing diameter by 1 inch with all things being equal increases rpm by 500. If that is true then I could increase pitch a little and use a 4 blade. Does anyone have knowledge of that?

 

[Sea Rider]

With black max prop, at which wot rpm is engine running to reach 24MPH as loaded? If over propped, with hub issues, hole shot will be awful. Was deck weight evenly distributed on deck during test ? Is engine healthy.

Don't think that by reducing 1/2" prop diameter OB will gain + 500 wot revs still maintaining same unaltered diam, that's what engine will achieve going down 2 less pitches if "thumb rule" applies.

Happy Boating

 

[carolynrose]

WOT is 4400 at 24 mph trimmed and maximum attitude with three adults and gear as I mentioned. The engine runs great and really nothing has changed except I had to change my prop to the backup. This was my backup that forced me to seek a better prop. So I know there is performance to be gained. Like I said I was hoping to get a stern lift prop, most of the 4 blades from Solas claim better stern lift. I estimated about 36% slip from my WOT speed and rpm, which is terrible.

 

[jimmbo]

Why are you trimming out to raise the bow, but you want a Stern lifting prop? Raising the stern just drives the bow into the water. If your engine is straining to get to the middle of the rpm range, a 4th blade is just going to make it worse, unless you drop at least a couple of inches in pitch.
Mercury makes some props you might be interested in
https://www.mercurymarine.com/en/ca/propellers/all/
Black Max(AL) can be had in pitches less than 12". There are several SS models that go 13" or lower

I run an Enertia, as you can see by my Avatar, it holds the whole boat out of the water, with very little positive trim

 

[carolynrose]

I guess I phrased that wrong, I was trying to say the attitude of the boat to get the maximum speed. The boat struggles to get on plane due to it's weight and the fact that it is a sterndrive. I was looking for a sternlifting prop which it seems like there a lot of choices in 4 blades. My thinking was to go a little less diameter because it's a 4 blade and maybe be able to up the pitch somewhat, it doesn't seem like there are choices for less pitch than 15