Will changing from factory aluminum prop to SS aftermarket increase rpm's

[4.3sunbird]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

walleyehed: <br />since you mess with so many props can you look at my thread <br /> <br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=24;t=014200;p=#000003

 

[walleyehed]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

I've posted a few questions for ya sunbird...

 

[Scali]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Walleyehead,<br />after having taken out a lower unit after striking slab of cement with an SS prop & seeing this happen 3 times in 3 years where I docked @ my last marina before I started trailering & hearing from other boaters, reading posts about SS props taking out LU's when striking rocks pretty easily .. As I mentioned I " respectfully " do not believe that when a direct hit occurs with a SS prop on a rock that 9 out of ten times the hub slips resulting in no damage as you quoted.....<br />Sorry.. Maybe 10 % of the time the hub will slip resulting in no damage..<br />Been there, done that, seen it a few times..<br />You mentioned you test props for a living ?<br />You run them into rocks ?

 

[walleyehed]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

You mentioned you test props for a living ?<br />You run them into rocks ?

I test props part-time, as well as new trinkets from some marine manufacturers...as for your question...<br />Yes, I have...I've run into rocks that bent blades badly, and have sheared a skeg clear off on one occasion, and never have I damaged a lower unit, gears or propshaft....I have spun more than my share of hubs though.<br />To be honest with you, I've seen about as many lower unit failures with aluminum props as I have from direct lower unit strikes where it wouldn't have mattered whether it was SS or aluminum...hitting a blade is one thing, smacking the front of the gearcase is another.

 

[moderator1]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Moving to the new Prop questions and Topics forum in General boating...

 

[Salmonseeker]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Hi again guys,<br /><br />I took the boat out today, <br /><br />I raised my motor up 2 holes, its is now 1 from the top. <br />The motor accelerates slightly better as long as the trim is all the way down. With the trim level the prop will lose its bite and over rev. Lowereing the trim stops this. <br /><br />At WOT the boat runs 5400 rpm at 32 mph. However any slight wave or steering wheel movement and the prop loses its bite and over revs(its just barely holding on). I can get the trim as high as level on the gauge before it over revs.<br /><br />During turns using anything over 1/4 throttle and the prop loses bite and over revs, even with the trim all the way down.<br /><br />In conclusion, I don't believe raising my motor is gonna solve this problem. I only gained 300 rpm and made this boat a very tricky ride to control. <br /><br />I would think dropping a pitch would help but as I have already tried with no luck.<br /><br />Any suggestions,<br />Thanks in advance Jason

 

[walleyehed]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Lift the engine one hole and test.<br />

I test one hole at a time and this is why....<br />You have 2 options, and a 300RPM gain is nothing to laugh about...that's great!<br />Now, we need to make the decision as to whether we want to settle for one hole down and change props..???? Or, do we want to try a prop designed to run at the heigth you are now and add speed and economy with a higher tech prop.<br /><br />Another quick question...is your engine a 2 cylinder, or 3?? If it's a 2 cylinder, is it an E-Tec??

 

[stratus5]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Originally posted by fisherman38:<br /> Hi again guys,<br /><br />I took the boat out today, <br /><br />I raised my motor up 2 holes, its is now 1 from the top. <br />The motor accelerates slightly better as long as the trim is all the way down. With the trim level the prop will lose its bite and over rev. Lowereing the trim stops this. <br /><br />At WOT the boat runs 5400 rpm at 33 mph. However any slight wave or steering wheel movement and the prop loses its bite and over revs(its just barely holding on). I can get the trim as high as level on the gauge before it over revs.<br /><br />During turns using anything over 1/4 throttle and the prop loses bite and over revs, even with the trim all the way down.<br /><br />In conclusion, I don't believe raising my motor is gonna solve this problem. I only gained 300 rpm and made this boat a very tricky ride to control. <br /><br />I would think dropping a pitch would help but as I have already tried with no luck.<br /><br />Any suggestions,<br />Thanks in advance Jason

From your first post, it seems you have dropped pitch AND diameter, from 12.25 17 to 11.75 15. <br />I would bet a 12.25 15 would be right.<br />-Dan

 

[Salmonseeker]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

The motor is a 2 cylinder and is not an e-tec. <br />What type of prop would you guys recommend?<br /><br />Jason

 

[Salmonseeker]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Hi again,<br /><br />I spoke with a boat dealer today. He told me I should put my motor lower than the original position which was as low as it could be. He says I need to lower it with a plate and then put on the 11 3/4 x 15 Rapture I have. He thinks the prop should work very well deeper in the water. Lowering it will be a big job and cost some. I only want to do that if it will really help. <br /><br />My question, who do I listen to? raising it or lower it? Which prop will work best? Should I buy a new one?. <br /><br />Thanks,confused

 

[walleyehed]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Lowering the engine is the last thing we want to do...especially lower than the existing transom.<br />Hang tight and give me a bit of think time....

 

[walleyehed]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

We gained 300RPM by raising it, and the speed went up too..Now I think you will agree, we are headed in the right direction, No???<br />Lowering the engine as suggested by that dealer is one of the screwiest things I've heard yet..the result would be lower RPM, and much lower speed...not what we are looking for.<br />I'm not a huge fan of the Rapture, I've ran several and the numbers don't impress me when compared to other props of simular cost.<br />I think if you are going to buy a prop, I'd look at a Turbo Hot Shot in 11-3/4X16, or a Stiletto TriadII, P/N 22316, also 11-3/4X16. The Turbo would be my first choice because I know it will hook up with the engine mounted right where it is...the Stiletto may run at that heigth as well..both props are much better suited to the mounting heigth you have.<br />Price range on these is 200 to 230.<br />Another option you have would be to have a prop shop add some cup to your 15 Rapture to bring the R's down.<br />With a "good" prop, it should run relatively well at the heigth you are..you could drop it one and see what ya get, but the aluminum prop isn't going to run as high as the props I've mentioned.

 

[Salmonseeker]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Thanks Kenny, <br /><br />I agree we must be doing something right. I don't want to lower the engine lower than the transom. I doubt Crestliner made a mistake on the transom height when they made this boat. The boat says it takes a 20in longshaft and thats what I have. <br /><br />I might just try one of those props you suggested starting with the Turbo. I actually never knew you could buy a 16 pitch, I thought all props jump from 15-17. Learn something new everyday.<br /><br />One question though, will this prop run better in turns with my higher engine height? Right now it is terrible with my aluminum prop at this height.<br /><br />Thanks guys Jason

 

[walleyehed]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Yes, the Turbo has alot more "Bite" built into it, and it will surprise you how high it will run.<br />Any prop may "Vent" in turns when trimmed up...some more than others...It is common practice to trim in slightly before a turn to avoid this, and for some reason, a prop will vent more at lower than WOT more easily.

 

[Salmonseeker]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Okay sounds convincing, I did a search and found a Turbo Hot Shot 11-3/4X16. The lowest price I could find was $229 plus $12 shipping. I am gonna go ahead and get it. <br />Once I get it I will let you know how it works.<br /><br />Jason

 

[dobers]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

why go aftermarket why not get an omc prop from your dealer just wonderein??

 

[walleyehed]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

dobers, the Turbo is a specialty prop, and has every bit of, if not more, technology than stock, OEM...In fact, BRP doesn't make a prop comparable to the Turbo I recommended.

 

[Salmonseeker]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Well I got an email today from the place I bought the prop from issuing me a refund. They said they won't ship props to Canada this season due to low volume of orders. They gave me a full refund so no real loss. I did want the prop though.<br /><br />On the bright side, I found a place online who were having a sale on Turbo Hot Shot. They only had some sizes listed online, so I gave them a call. They had a 11-3/4x16 Turbo Hot shot in stock for $199 and would ship to Canada.<br /><br />So a bad email in the end saves me $30.<br /><br />I will test when it gets here and let you know the outcome.<br /><br />Jason

 

[Salmonseeker]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Okay the new prop finally arrived, 11-3/4x16 Turbo Hot Shot.<br /><br />Took it out today and here are the results. The boat would get on plane very well and speed up with the trim down. WOT the boat ran at 31mph at 5600 rpm with trim down. If I moved the trim to 1/8 the prop would lose bite and over rev.<br /><br />I then lowered the motor one hole with no real change. WOT was 32mph at 5500 rpm with trim slightly below 1/4. If I trimmed to 1/4 or higher the prop would lose bite and overrev. Durning slight turns at high speed I would have to trim in slightly to stop the prop from losing bite. During a sharp slow turn the motor would have to be trimmed all the way in and could not be given anything over 1/2-3/4 throttle or the prop would lose bite.<br /><br />In conclusion, my rpm's went up with the new prop. Holeshot is deffinally better. Top speed is about the same.<br />However during full spead the stock prop seemed to have more bite?. I could run the trim and motor higher during WOT then the Turbo before losing bite.<br /><br />Overall the new prop seems to perform better. I am just wondering if I should lower it one more hole?(all the way down). Just so I can get it to grab better?<br /><br />Thanks in advance, Jason

 

[Salmonseeker]

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

I just put my numbers through a prop calculator. My prop slip improved with the new prop. I am now at 7% slip with the Turbo Hot Shot, I was at 10% with the OEM prop. So this is a good sign.<br />I also checked the trim out. When my trim guage says its at 1/8, the AV plate is parallel with the bottom of the hull. Is this right?