Has anyone ever ACTUALLY EXPERIENCED prop burn from a 1235 on a 210?

[TRBenj]

If the Acme 2133 14x13.5 5-blade will get 3k lbs of ballast (+people) out of the water more efficiently than the 1579 13.5x14.25 that is on the boat now AND run lower rpms at speed, it just seems like the best of both worlds to me, and I would buy the prop in a heart-beat. I need someone to let me buy it, but swap it out for a 4-blade if it doesn't do what i want it to do.

Ive run a number of 3 and 4-blades... so unless there are some weird physics with the 5th blade going on, I would expect the following general rules to hold true:

1) More blades in the water = improved holeshot... but less efficient at top speed (lower top end)
2) Pitch is pitch (regardless of blade count). More pitch = worse holeshot and decreased RPM's across the band. Opposite for less pitch.
3) Diameter is diameter. Larger = better holeshot, and will bring down RPM's at speed slightly. Smaller = more efficient (higher top speed).

I cannot see a prop that has 3/4" less pitch running fewer RPM's at speed. The 1/2" larger diameter will offset it a little, but not all the way. I can certainly see the larger diameter, lower pitched, extra-bladed prop coming out of the hole noticeably better though.

Both Delta and Acme will allow you to return a prop for a credit towards another one within a certain grace period (30 days?). Delta can sell at a much reduced price though, as Acme's policy dictates they sell for full retail in order to protect their dealers.

[Erik]

Sorry for the ignorance but what is "prop burn"?
Is it scarring of the gelcoat immediately above & behind the prop due to the prop moving "excessive RPM's" which in turn are moving "excessive ballast" causing a mark on the boat itself? Wow!

Please also note that when you google "prop burn", this thread is like the 3rd result in Google organic search so it's not like this term is exactly everywhere. I have never heard of it.

[TRBenj]

Sorry for the ignorance but what is "prop burn"?
Is it scarring of the gelcoat immediately above & behind the prop due to the prop moving "excessive RPM's" which in turn are moving "excessive ballast" causing a mark on the boat itself? Wow!

Please also note that when you google "prop burn", this thread is like the 3rd result in Google organic search so it's not like this term is exactly everywhere. I have never heard of it.

Answer:

Prop burn doesnt happen instantly. It is very real, however.

Our BFN had a touch under 1/2" of clearance with the original prop:

[ATTACH=CONFIG]17775[/ATTACH]

The rudder and rudder port also took a huge beating.

The cause is inadequate clearance between the prop and hull. A minimum of 10% of the prop diameter is the general rule.

[OKWAKEBDR]

Answer:


The cause is inadequate clearance between the prop and hull. A minimum of 10% of the prop diameter is the general rule.

10% of prop diamer would imply 1.35" clearance on a 13.5" prop. The stock prop has less clearance than that. I don't think Nautique would put a prop on there that would cause prop burn - they'd have way too much warranty work, so I don't think that general rule applies to the new boats.

I believe Acme recommends not to go less than 3/4 of an inch.

[TRBenj]

10% of prop diamer would imply 1.35" clearance on a 13.5" prop. The stock prop has less clearance than that.

Youre correct... CC infringes on the classic guideline somewhat. I would agree that 3/4" is about the limit of my comfort level on my own boats.

[vanislwake]

Not an acme but an OJ XMP with same dimensions as the 1235 (14.5x14.25) on my 07 210 and it left a slight groove in the hull, only ran the prop for a month then removed it when I sold that boat.