Which Way Should I Go?

[Agoose]

I have a 1986 Century Meridian with a 454 and an Alpha One. The WOT is 4600 rpm. The prop. on the boat was 15 and quarter inch with a 17 pitch. The rpm's with the throttle three quarters open was around 3300. I tried an aluminum prop with a 15 pitch and it took longer to plane and the top end speed was lower. The stainless prop went 35 mph and the aluminum 32 mph.
Any help would be appreciated.

 

[Agoose]

Re: Which Way Should I Go?

I should say the first prop was stainless and it spun the bushing. It was a Quicksilver Mirage.
One question I have is the reason I lost performance because of the change from stainless to aluminum, or because of the pitch?

 

[Crownie2]

Re: Which Way Should I Go?

I can't tell you what the best prop in the world is for your boat, but I can tell you this: When the Merc Enertia was compared to the Mirage Plus it accelerated better and gave better top speed. Check the Merc website for more info.

They are expensive, though, so you want to be pretty sure of the pitch you need.

Just my thoughts. Bob

 

[Silvertip]

Re: Which Way Should I Go?

The best prop for one boat may not be the best prop for "all" boats. Do your research carefully.

 

[Agoose]

Re: Which Way Should I Go?

Thanks guys, I guess my new question would be, should I go up or down in pitch to increase rpm's. One mechanic
I talked to told me I should try an 11 pitch but that seems awful drastic.
When I posted on the engine repairs forum I was told it was important to increase the rpm's to lessen the strain on the motor.
One last question I have is WOT? Does it really mean to have my throttle buried?
I know I've seen the difinition on this forum before but I can't seem to find it.
Thanks again.

 

[Agoose]

Re: Which Way Should I Go?

Another consideration I have is the diameter of the prop.
Should I try to go a little bigger in diameter to 15 and a half from 15 and a quarter?
Or should I go down in diameter to 14 and a half.
Thanks for any help.

 

[tmh]

Re: Which Way Should I Go?

I'm new to all this prop science/alchemy stuff, but I was told WOT means just that - wide open. If you're testing at "3/4" throttle, you really can't compare props as your 3/4 can't be exact from test to test.

Also, with wind/into wind can have an impact so test under the same conditions. Test with what would be a "normal" load for you also.

Aluminum doesn't perform as well as SS at any speeds. Going DOWN in pitch should increase WOT rpm - approx. 200 rpm per 2" pitch drop is what I've seen folks here say. That's assuming the same or similar type prop. Lower pitch also should provide better hole shot.

Test at true WOT then report RPM, speed, etc. and you'll get some REAL help from the prop folks here. Also, tell them what it is you're looking for performance-wise - top end speed? hole shot? general cruising? etc.

 

[Agoose]

Re: Which Way Should I Go?

Any thoughts on the diameter of the prop.
I read that if you drop the size, from a 15 inch to a 14 inch, the prop. would spin faster increasing rpm's.
What would this do to performance?
The prop. I have now is junk and I'm looking at at least $300 for a new one over the internet. The places around here are alot more, $450 to $600. I just don't know if I can send them back if I'm wrong?
I'm not to concerned with speed, I just don't want to work my motor as hard as it has been working.
Thanks for the thoughts.

 

[Tail_Gunner]

Re: Which Way Should I Go?

There has been a lot of info posted lately by national reviewer's on 4 blade props and the speed they can achieve on I/O's I am beginning to come to the conclusion that the newer 4 blade prop's have increased there tech so well and provide so much lift (bow stern or both) maybe it outweigh's the extra blade now.

I just went from a 19p 3bl alum to a 4bl 20p ss and the results were pretty kewl. I picked up 5mph but more importanly the boat now ride's much higher both @ wot and 40mph crusing speed and a muchly improved ride quality (smoother on a chop). I guess i should add i had the hp to turn the blades (225 on a 2800lb boat) I guess the only way to be conclusive on this subject would be to take away

walleyheds outboard combo and stuff him with a I/o for a year or so..........8)

 

[Agoose]

Re: Which Way Should I Go?

Thanks for the idea.
Now I have another thing to think about! LOL!
I guess I have something else to research.

 

[Ron G]

Re: Which Way Should I Go?

Lets slow down here a little for us with weak mindsdyour wot right now is 4600.i think thats about 200 under were it needs to be,what brand and model is the prop thats those numbers are from?iboats here have all kind of great deals on props.a stilleto maybe in your future.but lets wait and see what somebody else thinks.

 

[Tail_Gunner]

Re: Which Way Should I Go?

Umm no mention of STILLETTO here.............

 

[Agoose]

Re: Which Way Should I Go?

The desired WOT is 4600 and I was getting 3300 with a 3/4 throttle. I believe it will top out at 3600. The speed will be somewhere around 38 mph.
I have a 454 with an Alpha One.
The prop on it was a Quicksilver Mirage, model #
48 18278 A41 17P.
It's 15 and 1/4 inch diameter with a 17 pitch.
The prop is junk and I need a new one.
I'm figuring a 15 and 1/2 inch with a 15 pitch.
Any thoughts?

 

[tmh]

Re: Which Way Should I Go?

The desired WOT is 4600 and I was getting 3300 with a 3/4 throttle. I believe it will top out at 3600. The speed will be somewhere around 38 mph.

I guess I'm missing something here - why can't you find out what the CURRENT WOT is rather than a wild guess? If it truely IS 3600, you have serious issues and a 2" drop in pitch will only get you 1/4 of the way to the 1000 rpms you need to add!

I get the feeling this isn't going anywhere as I haven't seen answers to any of the questions folks have when trying to help....

 

[Tail_Gunner]

Re: Which Way Should I Go?

I have a 1986 Century Meridian with a 454 and an Alpha One. The WOT is 4600 rpm. The prop. on the boat was 15 and quarter inch with a 17 pitch. The rpm's with the throttle three quarters open was around 3300. I tried an aluminum prop with a 15 pitch and it took longer to plane and the top end speed was lower. The stainless prop went 35 mph and the aluminum 32 mph.
Any help would be appreciated.

Umm you sure that's a alpha one leg and a 454 big block id look again. Anyway's maybe changing all of your fuel filters's (ethanol fuel will clog up a old fuel system) set of plug's maybe some wires a little seafoam for good measure, if it still dosn't spin up have your tach checked

Actually id check you tach first or what ever your please's you. Maybe a hop over to I/O's and get the engine dilema checked out...........

 

[Agoose]

Re: Which Way Should I Go?

Sorry Guys,
The boat is out of the water.
The I/O guys thought the motor was overloaded with the 15 and 1/4 inch prop with a 17 pitch.
I will check the tack but I do have to put a new prop on it to find some answers.
Ethanol gas is not a problem we don't have it in New Hampshire.
Any guesses on a starting point for a new prop?
The motor is definitely a 454, the only put on with the Alpha One a few years.

 

[Crownie2]

Re: Which Way Should I Go?

Yes, they did use the Alpha with the base 454 for a couple years.

You don't want to turn that engine over the current 4,600 RPM's. The Mirage is a large prop meant to be put behind big horsepower engines. It is possible that it is too much prop for your setup.

Good Luck!

Bob

 

[dragon3711]

Re: Which Way Should I Go?

You mentioned in the motor forum the motor had been repowered to a 454. Repowered from what? Is the outfrive gear ratio correct for a 454?

 

[Crownie2]

Re: Which Way Should I Go?

Whoa - now we are getting some more information!

We need to know the HP of the repower and the gear ratio of the lower unit!

If you could only get to 3,600 RPM's - yes, you are over propped!

I thought your original post was saying WOT was currently at 4,600 RPM's!

Bob

 

[Agoose]

Re: Which Way Should I Go?

I need to say that you guys are good! Very impressive!
The original motor was a 5.7 liter. The horsepower of the repower was 390.
How do I go about finding the gear ratio of the lower unit?
All I know is that it's original to the boat, vintage 1986.
I take it this isn't correct for a 454.