Nicer planing and better cruise

[midnightrider1818]

Ahoy there mates. Got a 89 Larson dc 215. It's a cruiser. 22 foot long cuddly cabin. Wanting prop advice. I boat in lake Erie so holeshot and good cruise is what I'm after. She has a mercruiser 230 hp 305 4 bbl carb couple to a alpha one. She has a little bit of a hard time getting on plane and wanting better performance. Right now I run about 3500 and that gets me 24 25 mph according to gps. I believe my rpms run a little high also she will run about 5100 rpms wot depending on weight and weather conditions. Right now the prop is 14.5 15 pitch vengeance according to my research. Was thinking ,maybe a 4 blade prop and also does this seem to be in the ballpark for what I have. Also I was thinking about maybe a whaletail or hydrafin but heard they put a lot of stress on the drive. Any inputs fellas. Not sure what boat weighs

 

[Texasmark]

4 blades help both your problems. Rule of thumb (from prop makers) going from 3 to 4 is drop an inch of pitch considering everything else to be equal. High performance props with rake and cupping will alter the expected performance and drop the rpms for a given pitch, regardless of the blade count if you go from plain Jane to high performance.

 

[Sea Rider]

What's the max wot rpm range for that motor factory stated ? How loaded do you usually go boating with, specify min and max number of passengers ? Will be good to know max wot rpm achieved with min and max passengers on flat calm water cond if that's possible.

Happy Boating

 

[midnightrider1818]

What's the max wot rpm range for that motor factory stated ? How loaded do you usually go boating with, specify min and max number of passengers ? Will be good to know max wot rpm achieved with min and max passengers on flat calm water cond if that's possible.

Happy Boating

4400 to 4800. I would rather be on the higher of the spectrum. I never run wide open anyways unless I get a little throttle happy. usually just two of us. Maybe the most would be 6 and that's very rarely. Mostly two. I run usually with 55 gallons of fuel. And that's about it.

 

[midnightrider1818]

I could get back with you on that rpm range I am pretty sure my tach is off so I was thinking of buying a cheap tach and just hooking it up to the motor to get a accurate reading

 

[jimmbo]

The 5 liter is not known for its Torque, and a 22 ft is going to be a lot for it. If you are over revving, the normal advice is to increase Pitch, as it will decrease rpms. It will also reduce acceleration. A 4 blade will bring the rpms down and help with mid range accleration. but it will still put a heavier load on the engine on initial acceleration, a vented prop may help. An Enertia may also be a good choice for your combo, it can offer better holeshot and better top speed. It will also make the boat feel lighter.
Once you get an accurate RPM reading...

 

[Sea Rider]

If 4800 wot revs is the max stated rpm range for that motor and have achieved max 5100 wot rpm with current prop, the motor is over revving + 300 rpm if we assume that was achieved with 2 souls on board. 300 + rpm is not a wow over revving number specialy if you don't like running full hammer down, if you add one more soul onboard max rpm will decrease to around its max wot rpm range which is excellent.

The only issue I see running current prop is that although will work fine with up to 3 souls onboard while revving to its full wot rpm range won't perform any good with 6 up, extrra load passing max wot rpm range achieved with 3 up is a wot rpm serial killer.

Once an induction tach has been installed, report max achieved wot rpm with 2-3 and 6 up, wot rpm numbers will decrease dramatically when more deck load is added, worse if all 6 are heavy adults.

Happy Boating

 

[Starcraft5834]

a big YUP to 4 blade... heavy boats perform best with one... as texasmark said....

 

[QBhoy]

That’s a hell of a small pitch prop for that set up. It should be like a rocket ship out the hole and over rev like mad.

 

[Sea Rider]

That’s a hell of a small pitch prop for that set up. It should be like a rocket ship out the hole and over rev like mad.

If you meant the current installed prop will surely over rev badly if with just one soul on board. Al least the OP knows that current prop is an excellent water performer for up to 3 souls, will surely find out it's bad for six after installing the tach and checking how wot rpm range drops near the min lugging side of the motor.

Personally if it were my combo would limit the max passengers to 4 up and check if motor runs to at least middle wot rpm range, the extra 2 boaters will need to stay on Terra Firme if like running full hammer down or at plane while killing the motor over lugging it badly with 6 souls.

OP could try 4 blade props, will need one as a starter and keep testing props till he dials one that performs well with 2 to 6 boaters in the middle to max wot rpm range if that's possible. With a heavy boat and motor not being powerful enough you should limit the max number of passengers.

Happy Boating

 

[QBhoy]

If you meant the current installed prop will surely over rev badly if with just one soul on board. Al least the OP knows that current prop is an excellent water performer for up to 3 souls, will surely find out it's bad for six after installing the tach and checking how wot rpm range drops near the min lugging side of the motor.

Personally if it were my combo would limit the max passengers to 4 up and check if motor runs to at least middle wot rpm range, the extra 2 boaters will need to stay on Terra Firme if like running full hammer down or at plane while killing the motor over lugging it badly with 6 souls.

OP could try 4 blade props, will need one as a starter and keep testing props till he dials one that performs well with 2 to 6 boaters in the middle to max wot rpm range if that's possible. With a heavy boat and motor not being powerful enough you should limit the max number of passengers.

Happy Boating

Understood, but it’s definitely too small a pitch for that. The wot rpm and cruise data given are screaming out under propped

 

[Sea Rider]

Understood, but it’s definitely too small a pitch for that. The wot rpm and cruise data given are screaming out under propped

Untill the extra tach is not installed and working correctly to know if current tach reads same can't possibly state the current prop is way under propped when boating with variable loads. Right now is slightly over propped with 2 up. Will guarantee that with 6 souls on board the over revving with said under propped prop will be cancelled, that's if plan staying with current prop.

Happy Boating

 

[QBhoy]

Untill the extra tach is not installed and working correctly to know if current tach reads same can't possibly state the current prop is way under propped when boating with variable loads. Right now is slightly over propped with 2 up. Will guarantee that with 6 souls on board the over revving with said under propped prop will be cancelled, that's if plan staying with current prop.

Happy Boating

Hi sea rider.
There is no doubting your knowledge and input to this forum, but I need to disagree with you in this. Unless I’ve read it wrong it’s revving to 5000 rpm and cruise speed at mid 20’s is sky high on the current rpm gauge. It would make sense that’s it’s as accurate as they can be, especially with a 15”. I’ve never heard of a 15” on such a set up.
Youre right In that we don’t know all the facts, but surely your experience and mine would tell us that a 5.0, with and alpha and it’s likely ratio on a 21/22 ft cuddy would require a bigger pitch than a 15” any day of the week. All else being healthy of course.

 

[midnightrider1818]

Hi sea rider.
There is no doubting your knowledge and input to this forum, but I need to disagree with you in this. Unless I’ve read it wrong it’s revving to 5000 rpm and cruise speed at mid 20’s is sky high on the current rpm gauge. It would make sense that’s it’s as accurate as they can be, especially with a 15”. I’ve never heard of a 15” on such a set up.
Youre right In that we don’t know all the facts, but surely your experience and mine would tell us that a 5.0, with and alpha and it’s likely ratio on a 21/22 ft cuddy would require a bigger pitch than a 15” any day of the week. All else being healthy of course.

So I got me a test tach to see what I'm reving at wot. What pitch of prop do you normally see on this type of rig

 

[midnightrider1818]

Hi sea rider.
There is no doubting your knowledge and input to this forum, but I need to disagree with you in this. Unless I’ve read it wrong it’s revving to 5000 rpm and cruise speed at mid 20’s is sky high on the current rpm gauge. It would make sense that’s it’s as accurate as they can be, especially with a 15”. I’ve never heard of a 15” on such a set up.
Youre right In that we don’t know all the facts, but surely your experience and mine would tell us that a 5.0, with and alpha and it’s likely ratio on a 21/22 ft cuddy would require a bigger pitch than a 15” any day of the week. All else being healthy of course.

Ok I'm running at around 3200 rpm and getting low 20s. Maybe 23 24

 

[Sea Rider]

Was the test tach installed, set right ? there's 1800 wot revs difference between both tachs readings. Which type of tach is it ?

Don't think there's a "normally prop installed", in real boating world any motor has a min and max wot rpm range factory stated. Ideal would be to dial a prop for motor to works at least middle to max wot rpm range as usually loaded. Personally prefer the max rpm range which achieves a faster hole shot running with a fixed load.

Happy Boating

 

[QBhoy]

So I got me a test tach to see what I'm reving at wot. What pitch of prop do you normally see on this type of rig

At least a 17”...that would be on the low side and for water sports and high loads. 19” be more likely.
Only get out of jail card I’ll throw in is if the engine has been changed from a larger one to this and the ratio in the drive remains.
I think the health of your engine is now where I’d be looking. You are miles off the rpm range. To only get that rpm with a tiny 15” is verging on crazy.

 

[Sea Rider]

Would be ideal to know which test tach was used, how loaded, number of passengers were onboard when achieved max 3200 wot rpm. There's 1600 wot rpm difference between the max achieved and the max wot rpm range, which is a lot.

Happy Boating

 

[midnightrider1818]

Would be ideal to know which test tach was used, how loaded, number of passengers were onboard when achieved max 3200 wot rpm. There's 1600 wot rpm difference between the max achieved and the max wot rpm range, which is a lot.

Happy Boating

Ok I think you guys are reading it wrong or I am not being clear. I went out yesterday and hooked my test tach up. At wot with two adults and 3/4 tank of fuel. She holds 55 gal all together she would run 4700 to 4800 rpm that's with a 3 blade 14.5 15 pitch vengeance prop. So my rpms are perfect. Original tach is about 400 rpms higher. It showed 5100