Propeller Selection on new toy

[calkearn]

Hi all, First post for me here. I have a new 05 four winns funship deck boat w/5.0 270 gxi. Love the boat, great for family. Heres my prop story. The boat came stock with a 3 blade 19 pitch aluminum. After running it in (breakin) taking it easy. Started doing some WOT runs down the river and found it hitting the rev limiter (about 5200 rpms)when i trimmed it up where it ran nice and smooth. Did not like that nor did i like the ability to pull up a skier, sluggish (hole shot).<br />With the rpms being to high i figured i was under proped and wanting a better hole shot i went with a 4 blade(turbo prop) 18 pitch (everyone said to drop in pitch size when going to 4 blade).<br />Result great hole shot and pulled skier right up but really over reving at WOT and lost a ton of top end (about 10 mph) So i feel i am still under proped. Talked to Precision propellers about this and they recomended a 4 blade 20 pitch and would swap for no charge. Result with the 20 was great.<br />WOT rpm is now at 4800 to 4900 trimmed top speed is faster then the stock 19 3 blade aluminum, getting to 58 mph now. Hole shoot is good but havent tried pulloing up skier yet, but the boat planes fast and pulls hard.<br />Just thought i would let you know my findings, i have read a few posts on here and it has been helpful. Any comments would be appreciated. <br />Hope im not over proped now, hope it pulls up skier at least better than the stock 3 blade aluminum prop beacuse i really like the top speed and also the crusing speed, 3500 rpms runs about 35 mph and smooth as glass.

 

[QC]

Re: Propeller Selection on new toy

The only comment I have is that all of your test info appears to be with a very light load in the boat. I am thinking that with little fuel, one person and otherwise lightly loaded, that just at or slightly below the rev limiter is a good thing. If you want hole shot, you'll want the WOT RPM to be as high as possible. When you get the boat loaded down I could see the new prop only turning 4700 and now you are below the recommended WOT RPM. My .02

 

[calkearn]

Re: Propeller Selection on new toy

Well I had 3/4 tank of gas (50 gallon tank) 2 adults and 2 kids and gear (boards, vest, ect.) max recomended rpm is 5000. But i see what you mean, i dont want to be over proped thats for sure. If i had it my way i would like to get more HP out of this motor, it is new and not totally broken in yet so im thinking it will run stronger after a few more hrs on it. any tips on getting more HP out of a volvo penta 5.0 gxi ??<br />ordered a K&N air filter for it and i heard there is a restricter in the exhaust, what about reprograming the computer??

 

[walleyehed]

Re: Propeller Selection on new toy

That's where the 5.7L comes in....

 

[calkearn]

Re: Propeller Selection on new toy

Well yea that would be fine but this is a new boat, 5.7 wasnt an option, yes the 5.7 has 10 more hp, but i should be able to get 10 more hp out of this thing dont you think. I know if it were a car i could.....

 

[walleyehed]

Re: Propeller Selection on new toy

Depending on the Model of engine you are speaking of, the 5.7L should be about 45 more HP.<br />10HP will be next to undetectable, in fact, a daytime temp of 5-7 degrees higher than normal will rob more than 10HP

 

[TilliamWe]

Re: Propeller Selection on new toy

Calkearn, sorry to tell you, you are not going to get 10hp more out of that 5.0. Geez it already has 270! And 58mph is pretty good for a deckboat!<br />All the 5.7Gi would have given you (besides 280hp) would have been some more low end torque, but probably not enough to justify the price increase.<br /><br />Walleyehead, Volvo has their top 5.0GXi rated at 270hp. Then they have the 5.7Gi rated at 280, and then the 5.7GXi rated at 320. It ws the 5.7Gi that Cal was referring to.

 

[calkearn]

Re: Propeller Selection on new toy

Your Both right.. the 320 hp 5.7 isnt offered on my model. I would love to have 320 hp.... and yes tilliam 58 mph is really good for a deck boat or any 21' bow rider for that matter. But come on, you know the factory has to chock the motors to get them to pass, especially in california, so the has to be some hidden hp.

 

[calkearn]

Re: Propeller Selection on new toy

choke that is

 

[TilliamWe]

Re: Propeller Selection on new toy

Oh, there may be hidden hp, but it's not going to be easy to find. With MPI you've got the best injection system on a boat. Ok, if it had an O2 sensor, it would be better, but alas, boats don't have O2 sensors yet. If you don't already have open exhaust, that might free it up a little, but many feel that on a small block it's a negligible gain at best. Maybe under drive pulleys would help? But a little hard to come by. MAybe a better roller camshaft? Better rockers? Head work? <br />How much do you want to spend???

 

[calkearn]

Re: Propeller Selection on new toy

well i like to do it with bolt ons or computer programing. Do you know if the exhaust has a restricter in it? I know i could go internal and pump it up but dont want to do that until it has many many hours on it. How about the ignition MSD maybe? I have a K&N on order. But in my years of automotive experience a K&N, Computer programing Exhaust work and some sort of Ignition work will do the trick.(gets it breathing and burning better). Maybe an after market Intake. Dont know who can do the computer.

 

[TilliamWe]

Re: Propeller Selection on new toy

Do you know if the exhaust has a restricter in it?

He He He, nope, just it's overall design! Look at the manifolds, and remember, they have water completely surrounding them, so you know the exhaust passages are smallish. Then water gets introduced at the back of the riser. Then it goes through a "Y-Pipe" and down through the drive to exhaust at the hub.<br />K&N probably won't help any, because the factory screen is an arrestor, not a filter, they flow pretty well. But it might. Not sure who to tell you to have mess with the computer. that may open a can you'd best leave sealed.

 

[ramster]

Re: Propeller Selection on new toy

1.6 ratio roller rockers will give you a few HP, and thats an easy bolt on. Every one raves about Smart Tabs, and they are supposed to be add another 3-4 MPH. 58 is pretty fast for that size and weight boat, I only get 54 MPH out of my 19' glastron bowrider and that's much lighter than yours.

 

[calkearn]

Re: Propeller Selection on new toy

Thanks for the info, I put 1.6 roller rockers and longer pushrods on my 72 corvette and got a noticeable seat of the pants differance. <br />I really dont think messing with the computer will cause any proplems as long as its a pre programed map installed. Like on new cars, hyper tech makes a nice little programer you install yourself, plug it in and run it.<br />Some guy at the dealer said the tubes have restricters in them, i dont know, might open them up just to see. <br />I just see those california ultra low emmission stickers (not a bad thing) but low emission = low HP.

 

[QC]

Re: Propeller Selection on new toy

Originally posted by calkearn:<br /> Some guy at the dealer said the tubes have restricters in them, i dont know, might open them up just to see. <br />

Those aren't restrictors, they are "flappers" to keep water from going back up the exhaust and into the engine Leave them there. I think you'll get way more for your money if you spend more time on the water side of things: propellers, trim tabs, etc. BTW, I don't care what you do, you're not gonna find more than 2 - 3 MPH and that is unlikely. Like others have said, if those speed numbers are right, that thing rocks as is . . .

 

[calkearn]

Re: Propeller Selection on new toy

Thanks Cat, Yes the top speed is fine the only reason i am wanting more power (torque really) is for pulling up wake boarders, skiers and mid range punch. I know about smart tabs ect.. (might try them at a later date) but, I don't know, just hate leaving a stock motor stock. I am the kind of guy that puts a K&N and reprogrames the computer, changed exhaust on the wifes suv (tahoe) and got better performance (for pulling the boat) and better gas mileage.<br />You see i put that 4 blade 20 turbo prop on this thing and dont want to strian the motor. like i said wot is at 4800 rpms which is where it should be but would like the motor to be able to go to 5000 so i dont have to be wide open when getting places fast. (long rides down the river ect.) do you see what i mean?

 

[QC]

Re: Propeller Selection on new toy

Originally posted by calkearn:<br /> like i said wot is at 4800 rpms which is where it should be but would like the motor to be able to go to 5000 so i dont have to be wide open when getting places fast. (long rides down the river ect.) do you see what i mean?

I wouldn't worry about the WOT at cruise thing although it will shorten life. Think about it, if you set the engine up so it will pull that same prop at 5000 and then run 4800, the engine is making the same power. If that's all you really want then run her at WOT. If you want more stump pulling power AND the top speed that you have now, go with a Torque-Shift prop. They show up on Ebay fairly often. I sold one last year for around $425. Bondo is the man on Torque-Shifts. Do a search in both the I/O sections and the General Boating sections. Lots of good info there.

 

[Jdeagro]

Re: Propeller Selection on new toy

Calkearn;<br /><br />After you put the Smart Tabs on you will need to go back and re-prop. Why? Because the hull will be more efficient, and you will likely add 100 to 150 RPMs to the WOT. Same old story, HP + HP+ HP+HP "is the Answer". Not True!<br /><br />Don't forget to make the hull work for you too!<br />You don't see off shore racers putting 1500 HP on a Tug Boat and expect to win.

 

[calkearn]

Re: Propeller Selection on new toy

John, wow thanks, if thats true that will give me what i want, a tad bit more rpm. and i hear they help with hole shots, faster plane = quicker starts, Right ?<br /> Cat said "Think about it, if you set the engine up so it will pull that same prop at 5000 and then run 4800, the engine is making the same power. If that's all you really want then run her at WOT." <br />Well no because i would be burning more fuel and putting more load on motor. The more efficient a motor the less gas it burns and it doesnt have to work as hard.

 

[TilliamWe]

Re: Propeller Selection on new toy

cal the difference bewteen 4800 and 500 in fuel consumption won't be that much. It'll use a lot of fuel at either RPM!