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geomarq
05-02-2006, 10:20 AM
I want to convert my 20' Predator to diesel (currently gas) within the next few years... looking for suggestions.

What would the ideal powerplant be? Would this Cummings 4.2L 200hp be overkill? 400 ft/lbs of torque @ 2000 RPM burning just 3 GPH!

http://www.cmdmarine.com/4.2mi200.html
Kurt
05-02-2006, 11:40 AM
Not that I'm a diesel expert by any stretch of the imagination, but that's physically a pretty large/heavy engine to stick in a 20 footer (57" long and 30.2" high with trans and over 1000 lbs without trans). Also, you'd probably have to run a larger diameter / higher pitch prop to take advantage of the torque at lower engine RPM. There may not be enough room between the prop shaft and hull bottom to fit what is needed - just some thoughts that popped into my mind.

Compare that to 51" long and 28.5" high, with trans and 950 lbs, with trans for a Crusader 5.0/5.7 L gas engine.
Scratcher
05-02-2006, 01:11 PM
Steyr diesels have been getting some good press lately for smaller hp applications (that is under 500hp). Check to see if there is a dealer near you, otherwise parts and service might be an issue.
micky692002
05-02-2006, 05:57 PM
If I were you I would use the 170 hp. It fits perfectly and the cruising speed is between 27-28 knots and WOT around 34-35knots. There was a cc in here with the 170 for sale. The guy used the same 1 inch shaft and his prop was a 15 x 15. You'll have to change the exhaust and the water intake. If you want something smaller there is a 125 hp Yanmar. I've got the 100hp.
Eyekymo
05-04-2006, 10:32 PM
On my 20, I have a 13" x13 lh, like most, I guess. If I was to go to 13.5", I would be hitting the keel guard. I suppose you could shorten the guard up a bit, but it's there to protect the prop, so I'd give it some serious thought first.

Mike
micky692002
05-05-2006, 03:52 AM
Eyekymo, my prop is 14 x 14 and it fits.
Kurt
05-05-2006, 11:47 AM
Eyekymo...

I have a 14 x 11 prop on my '98 20'. The keel shoe isn't the problem, as you said, that could be cut back - it's the clearance to the bottom of the hull that can't be changed without some major surgery. With the 14" dia prop, I only have ~5/8" clearance between the blade tips and the hull and, according to Mich Wheel, that's less clearance than desired.

Prop diameter selection is related to HP and pitch is related to engine/propshaft RPM.