45mph top speed sound about right to you?

[alamantia]

I have a 1987 wellcraft elite 222XL with what I believe to be the origional 5.7 / 260hp mercruiser and a alpha1 outdrive with a 1.5:1 ratio. I did a compression check to find all cylinders between 170 - 175 psi. I bought the boat 2 years ago and it had a 12" diameter 19" 3 blade aluminum prop. I attempted full throttle on my first time out with that prop and the boat shot up to 5500 rpm and I eased the throttle back down. I since bought a 13" diameter 21" 3 blade aluminum prop and now I can go to full throttle at 4500 rpm and about 45mph on the GPS. Does that sound about right? a 25 year old 4000lbs (dry) boat topping out at that speed and RPM? I mean the boat sounds and feels good at that speed. Sometimes I wonder about 4 blade and stainless steel props. I woulder if I could get better performance trying different props. From my novice experiance I would think that I have it dialed in pretty decent unless I am grossly wrong and there is some way to get another 5-10mph out of it that I am completly overlooking???

 

[tpenfield]

Re: 45mph top speed sound about right to you?

13" diameter is still on the small side for an alpha 1 and 260 hp engine . . . speed seems OK

 

[sweet addiction]

Re: 45mph top speed sound about right to you?

What is the WOT range for that motor? If top speed is what you are looking for than I think you should go with a 3 blade stainless in a pitch and diameter that will have the RPMs at the top of the recommended WOT range.

I agree with Tpenfield on the 13" dia. prop....To put it into perspective....I run a 14 1/4 dia. stainless on my 3.0LX(135 h.p.) powered boat.

 

[alamantia]

Re: 45mph top speed sound about right to you?

13" diameter is still on the small side for an alpha 1 and 260 hp engine . . . speed seems OK

you know what... your right. My new prop is not 13" in diamater, it is 14.25" in diameter.

Old prop was 13" diameter and a 19" pitch
New prop is 14.25" diamater and a 21" pitch (full throttle is 4500)

I dont know what the redline is for that motor.

 

[sweet addiction]

Re: 45mph top speed sound about right to you?

14.25 X 21 is more like it. I think that you could do at least a 14.25 X 23 stainless. Or for sure try a 14.25 X21 stainless. The difference between aluminum and stainless is astounding.

 

[jestor68]

Re: 45mph top speed sound about right to you?

RPM range is 4200-4600.

 

[emilsr]

Re: 45mph top speed sound about right to you?

You're dialed in pretty well. Might be able to turn a 23p stainless and pick up a mile or even 2 on the top end, but the difference won't be much. Stainless has other advantages though. I'd put one on my list to Santa.

 

[jestor68]

Re: 45mph top speed sound about right to you?

Those numbers work out to a 25% slip using the BAM calculator. If you run them through leaving the rpm blank and click on it, it says with a 12% slip that speed equals 3847 rpm.

I must be doing something wrong. Damn calculators.

For what it's worth, the Mercury prop selector comes up with a 18/19 pitch for that 3900 lb boat.

 

[emilsr]

Re: 45mph top speed sound about right to you?

Those numbers work out to a 25% slip using the BAM calculator. If you run them through leaving the rpm blank and click on it, it says with a 12% slip that speed equals 3847 rpm.

I must be doing something wrong. Damn calculators.

For what it's worth, the Mercury prop selector comes up with a 18/19 pitch for that 3900 lb boat.

Maybe not....garbage in/garbage out on the slip numbers. Just because a prop SAYS it's 23" of pitch doesn't mean it is. Along the same lines, just because the tach SAYS you're turning 4500 doesn't mean you are.

That Merc prop selector is crap though. Best to stay away from that thing.

 

[SkiDad]

Re: 45mph top speed sound about right to you?

slip does seem high but speed seems good to me. For reference my neighbor has a 3500 lb boat and it has a 5.0/260 - 21 pitch and it runs about 45 with a normal load in it. I wonder if a cupped stainless of the same size will get your better slip numbers and i few mph. I can't imagine you will gain more than 2 or 3 mph at best no matter what you do b/c you are running at the proper rpm range.

 

[sweet addiction]

Re: 45mph top speed sound about right to you?

Maybe not....garbage in/garbage out on the slip numbers. Just because a prop SAYS it's 23" of pitch doesn't mean it is. Along the same lines, just because the tach SAYS you're turning 4500 doesn't mean you are.

That Merc prop selector is crap though. Best to stay away from that thing.

I agree with EMILSR... There is sooooo much variance in prop design from brand to brand. Dia. and pitch are the main focus but what about cup and rake?

 

[sweet addiction]

Re: 45mph top speed sound about right to you?

Maybe not....garbage in/garbage out on the slip numbers. Just because a prop SAYS it's 23" of pitch doesn't mean it is. Along the same lines, just because the tach SAYS you're turning 4500 doesn't mean you are.

That Merc prop selector is crap though. Best to stay away from that thing.

I agree with EMILSR... There is sooooo much variance in prop design from brand to brand. Dia. and pitch are the main focus but what about cup and rake?

 

[emilsr]

Re: 45mph top speed sound about right to you?

I agree with EMILSR... There is sooooo much variance in prop design from brand to brand. Dia. and pitch are the main focus but what about cup and rake?

Even prop to prop within the same brand there are big differences. For example:

The 2 props I like on my boat right now are both made by Mercruiser. One (15 1/4 x 22) I can turn at 5,000rpm, the other (14 5/8 x 21) I can only turn at 4800. "But wait" you say...."the prop with a larger diameter AND more pitch should turn slower"....and you'd be right "if all else was equal"....BUT....

The 22p prop actually measures 20 1/2" of pitch on my handy dandy prop jig, and the 21p prop (which measures exactly 21" on the jig) also has a bit of cupping, increasing the EFFECTIVE pitch by about half an inch. It also has more rake angle, but the effect is more how it lifts the bow than absorbing more power.

I'll be here all week. Try the veal. Don't forget to tip your waiter. :lol:

 

[jestor68]

Re: 45mph top speed sound about right to you?

Maybe not....garbage in/garbage out on the slip numbers. Just because a prop SAYS it's 23" of pitch doesn't mean it is. Along the same lines, just because the tach SAYS you're turning 4500 doesn't mean you are.

That Merc prop selector is crap though. Best to stay away from that thing.

I disagree that the Mercury prop selector is crap. It's the best I have found.

I'm a little surprised that you guys thinks that a 25% slip is OK in a V hull boat.

The slip calculator indicates that he should do 48 mph with a 12% slip at 4500 rpm using a 19 pitch prop.

His tach is wrong and he has the wrong pitch prop on his boat.

He needs to verify the accuracy of his tach before he ruins his engine from lugging it.

 

[sweet addiction]

Re: 45mph top speed sound about right to you?

Even prop to prop within the same brand there are big differences. For example:

The 2 props I like on my boat right now are both made by Mercruiser. One (15 1/4 x 22) I can turn at 5,000rpm, the other (14 5/8 x 21) I can only turn at 4800. "But wait" you say...."the prop with a larger diameter AND more pitch should turn slower"....and you'd be right "if all else was equal"....BUT....

The 22p prop actually measures 20 1/2" of pitch on my handy dandy prop jig, and the 21p prop (which measures exactly 21" on the jig) also has a bit of cupping, increasing the EFFECTIVE pitch by about half an inch. It also has more rake angle, but the effect is more how it lifts the bow than absorbing more power.

I'll be here all week. Try the veal. Don't forget to tip your waiter. :lol:

My point exactly. I run a Tuning Point 14.25 X 23 3 blade stainless on my 18' foot Glastron with an 3.0LX I/O and people think I'm nuts/ full of sh#t!!! Well for MY situation it WORKS! I'm within the WOT range. By the way, EMILSR I do love veal brats.

 

[emilsr]

Re: 45mph top speed sound about right to you?

I disagree that the Mercury prop selector is crap. It's the best I have found.

I'm a little surprised that you guys thinks that a 25% slip is OK in a V hull boat.

The slip calculator indicates that he should do 48 mph with a 12% slip at 4500 rpm using a 19 pitch prop.

His tach is wrong and he has the wrong pitch prop on his boat.



The speed calculator gives him a potential speed of 53 mph. The slip calculator says with a 19 pitch at 4500 rpm, he should realize 48 mph with a 12% slip.

I didn't say it wasn't the best prop selector online, but it's wrong more often than not....this is just another example.

A deep V boat, especially a day cruiser like the OP's boat, is NEVER going to run with 12% prop slip (unless you fudge the numbers). 18-20 is probably as good as it gets, and there isn't anything inherently wrong with 25% slip so long as the boat performs properly (and it sounds like it is).

And, yes, you can still add material to stainless props. :facepalm:

 

[sweet addiction]

Re: 45mph top speed sound about right to you?

There is sooooo much room for actual weight variance in a boat/owner situation. Use a "prop calculator " all you want...The bottom line is that it is just a guidance.

 

[jestor68]

Re: 45mph top speed sound about right to you?

To the OP: Verify the accuracy of your tachometer. Not doing so could be a very expensive mistake.

 

[alamantia]

Re: 45mph top speed sound about right to you?

To the OP: Verify the accuracy of your tachometer. Not doing so could be a very expensive mistake.

Its probably close. chevy 350's are pretty hard to kill anyway.

I was curiouls last night and did a little research on my phone and I saw this artical written when my boat was new, back in the Reagan administration... ha! and with the base 260 it says the boat can reach a top speed of 49mph. So with a 25 year old motor I only seem about 4mph off. Thats close enough for me.

Boating World Magazine | The Leader in Recreational Trailerboating

Good insight guys. One question though. When I come back to port on the hudson at low tied I always manage to kick up some mud and lightly nick up my prop. It got pretty chipped up last year so I took it off and brought it to work and had our welded run a bead around the outter edge, then I shaped it in the grinder and buffed it out and painted it. Seems to work fine. I have heard in addition to spending 2-3 times as much on a stainless prop, that if i were to hit a rock, rather than nick up the blade I run the risk of damaging my drive. Makes sense right? Id rather lop off a blade on a $100 prop that I could probabkly fix myself at work rather than ding up a $400 stainless prop and let the drive take the shock right? I see there is this lottle plastic looking piece in the hub, is that supposed to break away?

Thanks for all the advise. I always grew up around boats with my father having a few, but I have never owened my own boat until last year. I like learning tricks of the trade so to speak.

 

[emilsr]

Re: 45mph top speed sound about right to you?

Stainless props breaking drives is an old wive's tale. If you hit something that hard the delrin hub will break first.

Mud and sand won't hurt a stainless prop, but if you do hit a rock it'll be more expensive to repair than aluminum.