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Old 05-11-2014, 01:01 PM   #7
janice142's Avatar
City: St. Pete, FL
Country: USofA
Vessel Name: Seaweed
Vessel Model: Schucker mini-trawler
Join Date: Oct 2011
Posts: 1,041
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These latest two tests were done at the dock -- stern tied so thrust was all forward (no sideways strain possible)

The initial was done underway (when we had the overheat issue/manifold cleared out since, and thermostat replaced)

When I'd asked about making my Teleflex tachometer work and was told "can't happen" ... well, there's obviously been communication disruption. I've ordered one of those indicated above (thanks AusCan) -- and with a step raised can zap the coupler for a reading.

Still, I remember on our 40'er though that after a time you/I knew the rpms because of the sound. Throttle position helped too but sound told the same story. Anyway, my Mother's Day present to me is a handheld tach. This one:
Non Contact Tach Tool Handheld Digital Laser Photo Tachometer Tester RPM Motors | eBay

Last night I did speak with the owner. As OC Diver says, she's got one bearing. The owner also suggested a smaller prop and it looks like Tuesday the diver will be by to swap 'em. Then more testing.


I did re-do the Vic calculator for five knots -- the actual speed I prefer versus hull speed and it tells me:
Speed & Power Calculations

Basic displacement speed and horsepower required
Displacement hull speed (1.34 X sqrt of waterline length): 5.99 Knots
Minimum horsepower required at propeller(s) for Hull speed: 15.3 HP

Calculations based on desired speed and available HP
HP required at propeller(s) for desired 5 knots speed: 8 HP
Estimated maximum speed with existing 15 horsepower:
This is the speed we will use for the propeller size. 6.03 Knots


Throttling back to 8hp used will increase my range though it's all moot so far -- until everything is spot on, I'm not doing the one hour of diesel run. Bob told me I should use about a quart per hour at hull speed. I'm still a bit skeptical but I'll see you on the water, and hopefully NOT at the fuel dock too often.

Thanks for the information.
I may yet survive this engine swap.
Janice aboard Seaweed, living the good life afloat...
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