Props for 1994 35' Covertible

[kcummin]

I have just completed the installation of twin Cummins RECON 370B diesels, w/Zf220a at 1.5:1 ratios replacing original gas MP 454's w/ Hurth 630a 2.5:1.
We will be finishing plumbing and starting engines next week for the first time in preparation for sea trials.

Current props are 20x24x3 Bronze Hytorqs on 1.5" shafts, not sure if they were the Luhrs factory originals. Will be testing these props as well as a pair of 22x22x4 Michigan Nibrals that my yard has for sale.

I know with the Cummins 370B's I need to turn at least 3100RPMs to avoid engine overload.

Can some tell me what props the factory shipped with the diesel engines (CAT or Yanmar) in this boat. I'm getting wildly different recommendations from each prop shop that I talk to regarding size, pitch, materials, cavitation, etc. Lots of variables in the prop game.

At this point we are planning to capture all the performance data at sea trial, for the two sets of props, and then make decision on the right prop direction, with the help of a propscan/Hale MRI shop.

Thanks for any inputs and suggestions

Kevin

[Maximillion]

Hey kcummins,

When we test these engines at the factory we only shoot for 3000 RPM for wide open with a light load.

Back then, the Cat 3116 we used 21 x 24 3-blade with a light cup.
The Yanmar 315's ran with 21 x 25 4-blade dlat blade.

Hope this helps.

[kcummin]

Max,
Thanks so much for the info. It will help me to zero in on the correct set of props. We love our Luhrs which is why we made the committment to repower.

Kevin..

[Maximillion]

How did it go changing from Gas to Deisel?

[kcummin]

Max,

Repower - Still in progress, hope to start engines for first time later this week.
Gas to Diesel is a major amount of work(we started in December 2007), but my yard guys (Tolchester Marina in Md), specialize in the repowers, and are doing a great job.

They basically stripped everything inside the engine room and started rebuilding. New plumbing, new wiring, new gauges, new hoses, new gen...etc. I've been able to trace all ofthe wiring and plumbing runs for my documentation.

The hardest part was getting the custom risers designed and built to fit the boat. I followed Tony Athens recommendations on Boatdiesel.com, to make sure that we are using dry risers that inject water on the downslope and completely drain when at rest. We are also using his multi-stage fuel filtration setup.


P.S. Interesting note-, when we had the engine room stripped , I found a note written inside the hull, from the Luhrs factory. The note was: "Tom H. Undersides showing Improvement but needs detailing". This leads me to beleive that the factory has a good inspection/quality control function. I would like to do the factory tour in St. Augustine someday.

Here are a couple of in progress pictures:

BEFORE:52

AFTER:53

STBD RISER:54

PORT_RISER:55





Kevin

[Maximillion]

If your ever coming this way. Call ahead and we can schedule you in for the tour.

Engine work looks good.