Prop help 2002 35 lightning w 730 hp
#21
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Thanks Terry and everyone,
Allen I really don't want to break a bunch of drives though lol, if I run the 4 blade and stay away from the 5 blade that should help with that correct?
Allen I really don't want to break a bunch of drives though lol, if I run the 4 blade and stay away from the 5 blade that should help with that correct?
#22
My 26 Daytona was a totally different problem than you are having.
You are getting on plane and it sounds like you have it pretty much worked out.
I am not up on your X dimensions - How far is your prop shaft below the bottom of your boat?
The 5 blade prop is going to get you on plane faster but is going to cause a lot of transom lift and will not be as fast as a 4 blade.
IF you can get on plane normally ( for a performance boat ) with the 4 blade that is going to be you best all around prop for speed and handling.
The 5 blade causes more transom lift than the 4 blade and may cause ill handling such as bow steer and chine walk.
With my boat being a cat - they don't like transom lift. I did everything to settle the transom that I could.
A few stats
I redid the transom and raised the drive about 1 1/4 inches on the transom.
Than I installed a neutral extension box and mounted an IMCO -3 shorty lower mated to an X drive upper 1.36 ratio ( built by Mr. Gadgets)
This puts my prop shaft right at 2 inches above the lowest point on the bottom of the boat. This is the height that the race guru at Eliminator told me to do.
NOW the issues.
With a stock 28 pitch Bravo 4 blade the boat wouldn't go any faster than 5 MPH and blew out instantly.
My old Glastron had a high X also and to get the boat on plane I modified the trim rams ( shortened the rod 3/4 inch ) this mod allows the rams to collapse farther thus allowing the drive to tuck under farther ( negative trim ) there are other mods that have to be done to the transom assembly also.
I did this to my Daytona and this allowed the boat to get on plane with the 28 and a little better with a 5 blade Maximus. I was still getting too much transom lift so I cut the diffuser ring off both props.( the diffuser ring acts like a ski ) This stopped the excess transom lift but caused a problem getting on plane ( I had to go to 6000 RPM )
As SB said I blocked the exhaust passage at the top of the lower half using a piece of Lexan and 4200 to seal it air tight.
This fixed the problem and I was getting on plane like the diffuser rings were still there.
.I bought a BBlades labbed 28 Bravo and it would get on plane fairly normal for a cat. Prop slips so you just hold the RPM at 5000 and when you get to about 25 MPH you pull the throttle back and than re apply and it hooks up and hang on.
With the stock 28 my best top speed was 107 but most days it was 104 - The labbed 28 did 112 any time. - all props were at 6100 RPM
I am still working with props since my limiter is set at 6500.
You are getting on plane and it sounds like you have it pretty much worked out.
I am not up on your X dimensions - How far is your prop shaft below the bottom of your boat?
The 5 blade prop is going to get you on plane faster but is going to cause a lot of transom lift and will not be as fast as a 4 blade.
IF you can get on plane normally ( for a performance boat ) with the 4 blade that is going to be you best all around prop for speed and handling.
The 5 blade causes more transom lift than the 4 blade and may cause ill handling such as bow steer and chine walk.
With my boat being a cat - they don't like transom lift. I did everything to settle the transom that I could.
A few stats
I redid the transom and raised the drive about 1 1/4 inches on the transom.
Than I installed a neutral extension box and mounted an IMCO -3 shorty lower mated to an X drive upper 1.36 ratio ( built by Mr. Gadgets)
This puts my prop shaft right at 2 inches above the lowest point on the bottom of the boat. This is the height that the race guru at Eliminator told me to do.
NOW the issues.
With a stock 28 pitch Bravo 4 blade the boat wouldn't go any faster than 5 MPH and blew out instantly.
My old Glastron had a high X also and to get the boat on plane I modified the trim rams ( shortened the rod 3/4 inch ) this mod allows the rams to collapse farther thus allowing the drive to tuck under farther ( negative trim ) there are other mods that have to be done to the transom assembly also.
I did this to my Daytona and this allowed the boat to get on plane with the 28 and a little better with a 5 blade Maximus. I was still getting too much transom lift so I cut the diffuser ring off both props.( the diffuser ring acts like a ski ) This stopped the excess transom lift but caused a problem getting on plane ( I had to go to 6000 RPM )
As SB said I blocked the exhaust passage at the top of the lower half using a piece of Lexan and 4200 to seal it air tight.
This fixed the problem and I was getting on plane like the diffuser rings were still there.
.I bought a BBlades labbed 28 Bravo and it would get on plane fairly normal for a cat. Prop slips so you just hold the RPM at 5000 and when you get to about 25 MPH you pull the throttle back and than re apply and it hooks up and hang on.
With the stock 28 my best top speed was 107 but most days it was 104 - The labbed 28 did 112 any time. - all props were at 6100 RPM
I am still working with props since my limiter is set at 6500.
Last edited by Tinkerer; 06-21-2019 at 09:47 PM.
#23
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Have you guys with cut diffusers with twins that are having a hard time planing blocked the airflow thru the exhaust passage ? A few of us have with single engines with great results. Tinkerer with a Bravo 2"above transon in 26' cat and me to a small boat with alpha ss. Neither of the boats could get on plane with the diffusers cut until blocking the airflow thru the prop.. Oh,both boats thru hull exhaust...so just outside air going thru prop.
I haven't heard of anyone else trying,thus why bringing it up. .We usually bring this up in single engine threads.
I haven't heard of anyone else trying,thus why bringing it up. .We usually bring this up in single engine threads.
#24
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iTrader: (1)
Same with me, as I noted above in the Alpha SS case, it took a 2" rubber PVC cap.
What size did you use on the Bravo's ?
As you can see. Tinkerer blocked it another way. He did this so that the drive(s) could have water in them to help cool.
What size did you use on the Bravo's ?
As you can see. Tinkerer blocked it another way. He did this so that the drive(s) could have water in them to help cool.
#25
Also the joint between the upper and lower is not sealed and can suck in air at that point if you just block the opening at the front of the helmet.
I also sealed this joint above my piece of Lexan to make the exhaust passageway in the upper hold water. when on plane my entire drive is out of the water except for the skag below the bullet.
I have my excess water ( what would normally be going to the exhaust risers on stock exhaust ) dumping onto the top and sides of the upper to help cool it. all this seems to work since There isn't any chalking or discoloring at all.
I also sealed this joint above my piece of Lexan to make the exhaust passageway in the upper hold water. when on plane my entire drive is out of the water except for the skag below the bullet.
I have my excess water ( what would normally be going to the exhaust risers on stock exhaust ) dumping onto the top and sides of the upper to help cool it. all this seems to work since There isn't any chalking or discoloring at all.
#26
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I dont remember the size off the top of my head