|Topic Review (Newest First)|
|04-11-2010 08:44 PM|
|04-09-2010 11:40 PM|
Originally Posted by Omatako View Post
|04-09-2010 11:37 PM|
Originally Posted by sailingdog View Post
|04-09-2010 06:59 PM|
|04-09-2010 04:43 PM|
WOT will vary if you're tied to the dock as the prop isn't moving through the water as it should be and will generally encounter more resistance trying to move the water with the hull not moving.... so will reach a lower max RPM.
|04-09-2010 02:53 PM|
|lancelot9898||Using a photo tach is a good idea since my tach was out of calibration with actual readings lower than what I was reading. I have a Perkins 4-108 which was new in 1985 and I've been basically running with a too low WOT for the past 25 years so I'm not really sure how dire the consequences for over proping is on engine life. I do agree that approx 80% of WOT setting is a good number for cruising and saving on fuel. I also noticed that WOT varies with current. Tied at the slip my WOT setting is around 200 rpm lower than when I'm in open water. One thing I want to see is how this setting changes with current. My theory is that going against a current, my WOT rpm will be higher. How much is the real question. I do have a max prop and have varied the pitch to see how performance changes. FWIW WOT rpm is 2300 rpm and I cruise at 2000 rpm making 6 plus knots with a 37 ft Tayana.|
|04-08-2010 09:57 PM|
|ericroline||Do a speed RPM graph to find out the most efficient region for the engine. Diesels like to run at 80% of rated HP for the most efficient and long life area. I will run 2800, 2900 rpm for long periods backing off to around 2200, 2400 just to prevent running at one speed all the time.|
|04-06-2010 11:44 PM|
The hull is clean and so is the prop... so the prop is mismatched and you're not able to get anywhere near what the WOT RPMs should be... I'd say you're over-pitched by about THREE inches, since each inch will drop or raise the RPMs about 200 RPM. That would bring you up to 2600 RPM WOT... which is not bad for an engine that has a redline of 2800 RPM.
This would bring your cruising RPM up to about 2200 RPM, as suggested by Maine Sail. This should also lower your speed when idling.
Originally Posted by MobjackB32 View Post
|04-06-2010 11:26 PM|
|MobjackB32||The hull is clean and the prop was checked and cleaned 1 hour before the trip started. WOT in gear produces 2000 rpm, out of gear 2500+ rpm. She also runs about 3 mph at idle. the prop is large and 3 bladed. Large meaning just fits in the space within the full keel.|
|04-06-2010 05:59 PM|
|T37SOLARE||If the alternator has been upgraded then the RPM's on the tach are likely off. I'd get a hand held tach to confirm it correct before you make any drastic changes to the prop.|
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