FS33 FS44 prop hull burn?

[Tommywalton1974 175]

Not that this will help, I was reading and heard other boats have much larger props, is centurion ever going to go ahead and change the driveline geometry to hold a larger prop? Seems like they are backing themselves in a corner not doing that.

[h20king 794]

That would worry me too!!! It's really confusing that it burns on one but not the other. Could it be due to how the boat is commonly weighted then? Mrdeerwood uses QS more, I don't touch it. There has to be some difference.

 

Mrdeerwood, can you measure the clearance you have between prop and hull?

no I had burn on my white bottom 226 and only surf listed

[h20king 794]

I haven't heard of any of the 226's with bubble getting the burn. Issue was with the 2015's and no bubble. But they may have changed the prop diameter as well for 2016+?

Interesting that even your boats with the bubble are having the issue and it seems the issues have been isolated to 2015's on both brands???

I'm thinking more and more that the main cause might be related to QuickSurf being it was the first model release..................HMMMM

no I had it on my 14 226 but nothing yet on our 238 with the prop bubble

[stoked 1,039]

That would worry me too!!! It's really confusing that it burns on one but not the other. Could it be due to how the boat is commonly weighted then? Mrdeerwood uses QS more, I don't touch it. There has to be some difference.

Mrdeerwood, can you measure the clearance you have between prop and hull?no I had burn on my white bottom 226 and only surf listed

 

Do you know what your clearance was? Mrdeerwood and I have the same boat and prop and I have a little more than 1/4 inch more clearance than him

[h20king 794]

Yeah I had 5/8 clearance the difference in prop clearance would be caused by slightly different shaft strut mounting locations at the factory or one of you has a bad alignment form the factory

[DarksideR 1,679]

I know that the distance is going to play a huge roll in prop burn, but I really believe that the water itself plays a roll. Higher silt content in the water is basically an abbrasive that's going to act like a sand blaster in that turbulence. Or so I'd imagine.

 

I could also see some variance from boat to boat in hull thickness playing a part. But don't think a coloured hull is going to be thicker than a white one. Gelcoat is gelcoat. It's the first thing layer down in the mold. But these are hand built. Hand sprayed gel, hand layer fiberglass. All equipment installed by hand. There's gonna be some variance for sure.

[h20king 794]

If both of you have good alignment and struts are in the same location only other thing that would cause a difference in clearance is engine mounting location. Who even has more clearance has a engine mounted slightly closer to the transom

[h20king 794]

I know that the distance is going to play a huge roll in prop burn, but I really believe that the water itself plays a roll. Higher silt content in the water is basically an abbrasive that's going to act like a sand blaster in that turbulence. Or so I'd imagine.

I could also see some variance from boat to boat in hull thickness playing a part. But don't think a coloured hull is going to be thicker than a white one. Gelcoat is gelcoat. It's the first thing layer down in the mold. But these are hand built. Hand sprayed gel, hand layer fiberglass. All equipment installed by hand. There's gonna be some variance for sure.

I think it's more driving style if you try to make sure rudder is straight and ease into the throttle I think you will have less problems than the guy that nails the throttle each time

[Mrdeerwood 26]

I know that the distance is going to play a huge roll in prop burn, but I really believe that the water itself plays a roll. Higher silt content in the water is basically an abbrasive that's going to act like a sand blaster in that turbulence. Or so I'd imagine.

Agree on the silt for sure. Really don't think that caused mine though. The weekend it happened I was in a pretty clean lake surfing 40-90' deep water. If you are running back and forth across a section of water that gets below 10' then silt could easily come into play.

[Mrdeerwood 26]

[quote name="DarksideR" post="153111" timestamp

I could also see some variance from boat to boat in hull thickness playing a part. But don't think a coloured hull is going to be thicker than a white one. Gelcoat is gelcoat. It's the first thing layer down in the mold. But these are hand built. Hand sprayed gel, hand layer fiberglass. All equipment installed by hand. There's gonna be some variance for sure.

 

Definitely could see some variance since they are hand built. Guess I got the raw end of that deal...

[Mrdeerwood 26]

I think it's more driving style if you try to make sure rudder is straight and ease into the throttle I think you will have less problems than the guy that nails the throttle each time

As mentioned earlier, We always pull our riders out slow (I think it's easier) and I have been very cautious to center the rudder before power since my buddy got burnt... But agree that would contribute to cavitation/burn

[Mrdeerwood 26]

I'm going to throw out a quick summary of what I have gathered...

 

You have an increased chance of getting prop burn if...

1) you have less than 3/4" clearance

2) you have a high load (full ballast, using QS)

3) you drive in water with high silt content

4) you apply power quickly and/or don't have the rudder center

5) your running high RPM's at surf speed

 

Maybe not any one of those individually will get you burnt but a combo of those 5 will definitely get you prop burn.

[Tommywalton1974 175]

Under heavy load I wonder if the shaft flexes along the entire length. That's a lot of shaft not supported from the hull to the strut. I mean it is a spinning shaft and the water bearing in the strut allows for movement. If it's bowing some under load your 3/4" gap could be all of a sudden a 1/2"

[Mrdeerwood 26]

Under heavy load I wonder if the shaft flexes along the entire length. That's a lot of shaft not supported from the hull to the strut. I mean it is a spinning shaft and the water bearing in the strut allows for movement. If it's bowing some under load your 3/4" gap could be all of a sudden a 1/2"

Plus the prop blades swell (lengthen) under load...

[Tommywalton1974 175]

Plus the prop blades swell (lengthen) under load...

hmm.. You're right I can see that. Absolutely. That could add up in a hurry to a clearance issue for the burn.

 

I can't imagine the torsion on that shaft. It wants to flex. I wonder what the run out is between the strut and hull.

Edited August 13, 2016 by Tommywalton1974

[h20king 794]

I'm going to throw out a quick summary of what I have gathered...

You have an increased chance of getting prop burn if...

1) you have less than 3/4" clearance

2) you have a high load (full ballast, using QS)

3) you drive in water with high silt content

4) you apply power quickly and/or don't have the rudder center

5) your running high RPM's at surf speed

Maybe not any one of those individually will get you burnt but a combo of those 5 will definitely get you prop burn.

I agree I drive the same way my hull burn was slow and did not show much other than discoloration IE loss of shine untel after 150 hours at which time small sections of gel were ate away

[h20king 794]

Under heavy load I wonder if the shaft flexes along the entire length. That's a lot of shaft not supported from the hull to the strut. I mean it is a spinning shaft and the water bearing in the strut allows for movement. If it's bowing some under load your 3/4" gap could be all of a sudden a 1/2"

new pcm has the shaft going through the center of the v drive so way more support than shafts that connect with a coupler on the underside.

[h20king 794]

Here is a pic of the drive as you can see the shaft goes through the drive giving more support and uses a coupler on the back side.also makes alignment and shaft removal easier with better access to the mounting coupler.

[Tommywalton1974 175]

Here is a pic of the drive as you can see the shaft goes through the drive giving more support and uses a coupler on the back side.also makes alignment and shaft removal easier with better access to the mounting coupler.

that's cool. What I mean is the shaft is 1-1/8" and from the coupler at the hull down to the strut if the shaft bows under load, then the flex would transfer through the strut bearing to the end perhaps. It may not at all, it seems to me that a 1-1/4" shaft or bigger is what these big heavy boats need. The shaft just seems small like the prop diameter limitation.

 

It's just my mind thinking about it. Probably irrelevant. However I bet if these boats keep getting larger with massive gross weight, the manufactures better upgrade the drive line to larger stuff. I have a friend who had an 80's direct drive, can't remember the brand, he has the exact same prop shaft size as my 08 Enzo and his boat is tiny in comparison. That's all I mean.

[1911 4]

I may have missed it, but this is the first I've heard of making sure the rudder is centered before applying power. What does that affect and how? Thanks.