Prop and low speed planing

[Taciturn]

I've gotten alot of info off this site on this topic but am looking for input on my situation. I have a 98 Bayliner with the 5.0 and alpha one gen two. I was running a 19 pitch 3 blade prop (max speed 38mph rpm unknown)but was having a real hard time maintain a constant speed at 20mph. Anything over 24 it was fine probably due to the boat going on and off of plane. I tried adding weight to the bow and going to a 4 blade 16 pitch prop. I wanted a 17 but they are not available at the local prop store and they aren't very helpful in the knowledge department. Full throttle it ran 4800 rpm which is the max my owners manual says to go. It also got horrible mileage as it used a half a tank (20 gallons) in just a few hours. It held the speed better but still not great. It really yanked me out of the water though(so much so that iam injured). My question is if I go to am 18 pitch 4 blade will it provide any benefit over the 3 blade 19 pitch? I am wanting the better fuel mileage back but still want plane at slower speed to keep my speed constant. Thanks

 

[alldodge]

I've gotten alot of info off this site on this topic but am looking for input on my situation. I have a 98 Bayliner with the 5.0 and alpha one gen two. I was running a 19 pitch 3 blade prop (max speed 38mph rpm unknown)but was having a real hard time maintain a constant speed at 20mph. Anything over 24 it was fine probably due to the boat going on and off of plane. I tried adding weight to the bow and going to a 4 blade 16 pitch prop. I wanted a 17 but they are not available at the local prop store and they aren't very helpful in the knowledge department. Full throttle it ran 4800 rpm which is the max my owners manual says to go. It also got horrible mileage as it used a half a tank (20 gallons) in just a few hours. It held the speed better but still not great. It really yanked me out of the water though(so much so that iam injured). My question is if I go to am 18 pitch 4 blade will it provide any benefit over the 3 blade 19 pitch? I am wanting the better fuel mileage back but still want plane at slower speed to keep my speed constant. Thanks

Howdy

I don't think your going to get your current boat to do what you want. Sounds as your boat starts planning around 24MPH, so anything under that uses more fuel because your plowing. A 4 blade prop will give you more lift and some better hole shot but you don't want that. You get more lift only as you start planning.

 

[Taciturn]

I guess I'll just have to deal with paying for more gas which I wouldn't mind if it was perfect. I will have to try other things like a foil of some sort. I played with the trim but not as much as 25% which I saw some one had suggested in another thread. The new prop made it better but still a little more desired. Maybe prefect pass in the future...

 

[littlerayray]

Try a merc spitfire prob with the same pitch as your 3 blade I just put one on my boat and gained a cpl mph as well as popped outta the hole quick also I can stay on plane at lower speeds

 

[Rick Stephens]

I think your described need would be better served with trim tabs instead of prop change. (Sorry if I sound like a broken record, since I just posted this on another thread) You can lower your planing speed by quite a lot just installing the inexpensive and automatic Smart Tabs. Stepping up to electric or hydraulic tabs, you would gain the ability to adjust your tabs on the fly. On my smaller 17 foot boat I moved plane speed from 18-19 mph down to 12-13 mph. Big difference and both adds comfort, as the tabs absorb some of the pounding from crossing wakes or running in chop (my wife thinks I installed shock absorbers) and increases mileage since your boat planes out earlier.

Might not do everything you need to fix these issues, but is more likely than just a relatively minor change in props.

Rick

 

[alldodge]

Since you brought the foil up, I installed a Stingray foil (the real hard plastic type) on my Rinker years ago and it will stay on plane at a slower speed, about 3 MPH slower. My Rinker is 23 foot and 4800 pounds. This may help your issue, by how much I don't know if any.

The foil topic usually brings up a bunch of other comments

 

[mandmj]

Smart Tabs are a wonderful product to help w/ a lot of the problems you are describing. They worked wonders on an old 23' Wellcraft w/ an alpha 1 I had in the past.

 

[Bondo]

I have a 98 Bayliner with the 5.0 and alpha one gen two.

Ayuh,...... Welcome Aboard,..... Ya got the Wrong boat for what yer tryin' to do,.....

Ya need a ski-towboat,....

 

[Taciturn]

Ayuh,...... Welcome Aboard,..... Ya got the Wrong boat for what yer tryin' to do,.....

Ya need a ski-towboat,....

Ya I know however when I was shopping for a boat I wanted one that I could also fish out of. I just barely learned to wakeboard. I may upgrade next year to a more friendly wake board boat.

 

[ibrw1]

Larger diameter props use more fuel, also more blades. I used a 20 pitch 4 blade 14.3 diameter for years. Now I use a 21 Pitch, 3 blade 14.3 diameter.
Happier with the results.

I use fuel minder and GPS to calculate MPG. 202 Crownline BR 5.0 2bbl at 3.2 average mpg. Full synthetic oil and K&N marine air filter.

 

[southkogs]

For wake boarding you really don't want a ski boat ... a good tow boat will lay down a nice table for a skier, but you're lookin' for a fat ole' wake to board on. You don't need to plane slower, you need to plow ... add some ballast to the stern (fat sacks or something) and then figure out what speed she likes to go at.

Oh ... and save up some extra cash for gas If you want a fat wake to board on, ya' gotta' push a lotta' water and cut big waves.

 

[Rick Stephens]

I went through the same thing. My ski boat was really hard to keep on speed in the 17-19 MPH range for boarders. I tried going from a 17 in 3 blade to a 15 in 4 blade. The 15 inch is amazing how fast it pops up and how well it controls around the obstacles and docks. But it eats gas, and sounds like hell when trying to cruise. Makes the whole boat feel funny at higher speeds. And where I used to use 5-8 gallons a day, that went out the window and 12-15 became the norm.​

So I installed those much maligned Smart Tabs and went back to the 3 blade 17 in. My milage went up higher than ever, I trim the drive up and force the boat to stay bow high while pulling boarders. I can now set my throttle and mostly hold 18-19 while a boarder works the wake with minimal throttle management. Not a great wake, but an OK one when I keep the bow up. I basically have the drive trimmed out as far as is allowed underway.

Best of all, when I want to cruise up lake and go fishing, this boat's primary purpose, I can do so with decent speed and milage. I doubt I go back to that 4 blade even though it works just like it is supposed to.

I'm now swapping out the 3.0L 4 cyl for a 4.3L Vortec V6 and an Alpha GenII. I have it all to do over again figuring out my prop. Good thing I know that the words cheap and boat don't go together.

Rick