28 te prop removal

[RobS]

Hope not. Will look this afternoon when I start working on the fridge. That tranny looks like something out of Transformers going through metamorphosis. Hurst v-drives are pretty indestructable. So what got wrapped around the prop?

That one is a straight drive. I don't recall what the story was with it, I came across it a couple years ago when searching the net and saved the pic...

[Serenity]

The old prop is being sand blasted, welded and will be used as a spare. The prop is shot, including metal fatigue. The new prop is a state of the art three blade prop from Acme that will grab as much water as a 4 blade prop. If anyone on Long Island requires a prop puller with open end wrenches to take off the shaft nuts, I have one to loan out.

[Serenity]

Well, I picked up my new, improved, state of the art, capable of warp speed less a couple of warps and "trust me" greater fuel economy prop. See attached photo. The old refurbished prop is on the left, and the full figured one is on the right. As per Tommy at B&S, I should achieve greater rpms, less fuel consumption and greater speed. Let you know in the spring.

[RobS]

Very cool, looking fwd to the performance feedback. Can you post the dia, pitch and cup of each ?

[Serenity]

Rob as per my packing slip, the prop is Acme 18 X 17 X 3 LH 1-1/2 and that is what is on the prop. If you want call Tommy at B & S, he would have any other info you might be interested in. Enjoy

[Serenity]

The old prop was 18 X 17 L 1 1/2. It should work as a spare which I have no desire to use.

[RobS]

Thanks for the specs. Blowing up the photo it seems to have a good cup. Have you photo-tached your engine to check the accuracy of your dash tach? I can photo tach it for you in the spring if you wish, but my services don't come cheap. I would need 1 beer for every 1,000 rpm's

[jleonard]

Rob that IS cheap. But I work for beer too.

[Serenity]

Well you both can come over and sing " Om by ya" while we are all holding hands. Is that a beer per 1 rpm or per 1000 rpms? No, I used my old Polaroid to photo the shaft, but the developing process was somewhat slow. I will contact you in the Spring when she is launched. Thanks for the offer. I guess it pays to remember the brides name!

[Serenity]

Rob, two things. One I do not have a Yanmar Tach but an Aetna digital tach which was replaced when I first purchased the vessel. It would be interesting to see the comparison. Secondly, does the boat have to be in gear in order to achieve an accurate reading on the photo tach or can it be done at the dock?

[RobS]

I had the Yanmar factory panel:

0321091415.jpg

But as of last month it is no more:

2012-01-15_15-59-50_682.jpg

I am nearing completion of building my new dash which includes the Aetna digital tach:

DSCN6746.JPG

The photo tach is done at idle at the dock and then out at sea at WOT as well as any rpm in between. The transmission (gear) is not part of the equation. The photo tach counts the crankshaft revolutions right off the balancer via reflective tape and a laser pointer/beam.

The Aetna tach is said to be within 1rpm of accuracy. The 6LP has 117 flywheel teeth. So 117 PPR (pulses per revolution)

The tach dip switches are set as follows:

SW2: 0000
SW1: 01110101

0 = off position

[Serenity]

Rob, if you recall I had issues with the Aetna tach whereas I was getting readings of 5500 plus. If I rememeber correctly you thought I might have had a Yamaha not a Yanmar. The bottom line was Aetna had a problem with the the original tachs and have since corrected it. I have 2 Aetna tachs. The original Aetna tach was covered under warranty. Nice looking helm. Oh I picked up my Fridge today. Should be working on that this afternoon.

[RobS]

If I rememeber correctly you thought I might have had a Yamaha not a Yanmar.

I surely remember, these 6LP's turn some high rpms but not that high! Enjoy the nice weather out there this afternoon cause tomorrow is not gonna be so nice.

[jleonard]

Actually the correct procedure for calibrating you boat tach(s) is that you should be doing it at the dock. Engine warm in neutral at WOT or what is normally called "high idle".
This insures that the throttle cable is reaching full travel, and that the injection pump stop is correct. Since the engine uses basically zero horsepower in neutral, there is no load on the engine and this rpm is very repeatable, even if there is wear on the engine.
Once you know that the high idle is correct, you can then take a ride and check WOT under load. This will tell you if your engine is loaded properly ie over propped or under propped, you can check for black smoke, engine temp, egt, etc.

Running the engine at high idle does not hurt anything, it is only "scary feeling". I have done this many times on various boats and they are not always adjusted correctly from the factory, and not always correct from a injection shop if they go in for a rebuild.
Case in point, when I repowered my old Mainship with a new Cummins 6bta, the Cummins tech had her up to check high idle within 5 minutes of when I first got the engine fired up. THAT was scary. LOL (It happened to be right on the money).

[RobS]

When I first checked my WOT out at sea and was not happy with the results, 3,750, I then checked high idle (for reasons Jay noted above) and she easily hit 4,200 rpm. "Scary" is an understatement!