New Prop

[Froggy]

The prop on my now vintage Albin 28 TE is some 12 years old and showing signs of de-metaling on the hub. Rather than risk throwing a blade, I invested in a new 4 blade through Accutech. Sea trial later in the week will be defining but, in the meantime, I love the laser etched boat name on the prop. Thanks Accutech. Well done!

[Cape Codder]

Wow!! Nice!!

What diameter and pitch?

[Froggy]

Hi Bob,

It's 18 dia 17 pitch Michigan wheel with cupping. Previous prop was 18 square three blade. We dropped an inch in pitch to compensate for the 4 blade. I believe most are running 19 square but mine is a 1993 with a 315 Peninsular running through a 1.6 ratio transmission.

Carl

[DougSea]

That's purdy!!

I don't know that I could bring myself to paint over that!

[Froggy]

I thought about just mounting it over the fireplace but, nah, better on the boat....

[tugshughes]

"Froggy", I'm considering a change in props, hoping to get more speed out of our 1994 28' TE to give us a bit more speed. I was impressed with your 4-bladed prop from Accutech. How was your performance this past summer?

[Froggy]

Thanks for the question on the four blade prop. Sizing the prop was a bit of back an forth with Accutech. We wound up at 18 x 17. Initially, Accutech wanted a smaller diameter but Michigan was concerned she might throw a blade if we went too small so we went 18/17. The good news is that the boat is turbine smooth with the four blade and it increased cruise speed up to 20 knots or so at 2800 rpm. The bad news is that she doesn't have the torque to turn it much over 3100 rpm (vs 3600 nominal WOT). I'm actually ok with it as I was concerned about cruising speed and smoothness more than top end when I started this project. My recommendation (if I were to re-prop again) would be to drop to 18 x16 as you'll get somewhat more top end but still have good cruising and smoothness.

Carl

[Serenity]

I went through the same process of a new prop. However, I have a 315 Yanmar tied into a 1.6 peninsula tranny. Check out the post under "overloading". My results were outstanding.

[halfmoon]

Working with a new Acme prop, I have the advantage of experience. Not mine, but that of an experienced boat builder. 40 years building sportfishermen designed to run quickly out to the Gulf Stream. He used many of our Yanmars. He quickly determined that I am under propped. He also said that my engine, designed for continuous operation @ 3600 rpm, should be run at that rpm. WOT is just shy of 4000. 18 kts @ 3600, 20 @ WOT.

[Tree]

My buddy has just gone from a 19 x 19" cupped 4 blade on his 28TE to a 20 x 18" cupped four blade. His results are he can now get 23-24 knots at 3850 rpm and a cruise between 17-18 knots at 3300 rpm.

Prior to this, my boat was almost a knot faster than his at 3300 rpm as he could only acheive 15 - 16 knots and he couldn't achieve WOT, always falling 50 rpm short. We just put it down to him having a heavier boat (aircon, genset and stainless instead of plastic on all fittings).

Now he's got a better turn of speed than me!

He has all the data sheets for how the prop was worked out - i'll have to get them from him and upload them here.

It just shows how no two 28's are the same.

[RobS]

He has all the data sheets for how the prop was worked out - i'll have to get them from him and upload them here.

Please do.

It just shows how no two 28's are the same.

Amen

[Tree]

Not the best of images as he has just taken it with his iPhone as he doesn't have a scanner handy.

The data means nothing to me - hopefully its of use to someone else though.

[John_Madison CT]

Thanks for the question on the four blade prop. Sizing the prop was a bit of back an forth with Accutech. We wound up at 18 x 17. Initially, Accutech wanted a smaller diameter but Michigan was concerned she might throw a blade if we went too small so we went 18/17. The good news is that the boat is turbine smooth with the four blade and it increased cruise speed up to 20 knots or so at 2800 rpm. The bad news is that she doesn't have the torque to turn it much over 3100 rpm (vs 3600 nominal WOT). I'm actually ok with it as I was concerned about cruising speed and smoothness more than top end when I started this project. My recommendation (if I were to re-prop again) would be to drop to 18 x16 as you'll get somewhat more top end but still have good cruising and smoothness.

Carl

I'm no expert, but if the engine can only hit 3100RPM's then you're seriously lugging it. The "Beast" (aka Peninsular) is spec'd at WOT RPM 3600. Lugging a diesel will kill it quickly!

[Froggy]

I'm aware of that and am going to try to get the prop adjusted down a bit. Also, my cruise is 2800 rpm or so.

[Russell]

This article on engine loading might be of interest.