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Author Topic:   rpm vs wot

mag posted 07-06-2002 11:32 AM ET (US)
I have a 1979 175HP Johnson on a 20' Outrage. The specified full throttle operating range is 4500-5500, but the ocean swells normally limit my rpm to less than 3500. I am tempted to re-prop the motor to get the rpm closer to 4500 at 3/4 throttle, since that is about the most throttle I ever use. I would appreciate any comments on this idea.
JBCornwell posted 07-06-2002 08:49 PM ET (US)
Hi, Mag.
I think it is too risky to deliberately underprop your boat.
If the possibillity exists to over-rev and destroy, Murphy says it will happen.
Red sky at night. . .
JB :)
mag posted 07-07-2002 12:54 AM ET (US)
JB,
Thanks for the advice. I'll keep the prop I have. Maybe a smaller motor would eventually be a better solution?
-mag
Peter posted 07-07-2002 07:52 AM ET (US)
Keep the prop you have. There is no harm in running at 3500. Generally, the less time you operate in the WOT range, the longer your engine will last. It's probably lasted this long because its hardly run at WOT.
Bigshot posted 07-08-2002 01:59 PM ET (US)
WOT is where you want the engine to run at WOT. You can run all day at 1000...2000....3500 etc but when that thropttle is smashed to the console and trimmed it should be at 4500-5500.

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Author	Topic: rpm vs wot
mag	posted 07-06-2002 11:32 AM ET (US) I have a 1979 175HP Johnson on a 20' Outrage. The specified full throttle operating range is 4500-5500, but the ocean swells normally limit my rpm to less than 3500. I am tempted to re-prop the motor to get the rpm closer to 4500 at 3/4 throttle, since that is about the most throttle I ever use. I would appreciate any comments on this idea.
JBCornwell	posted 07-06-2002 08:49 PM ET (US) Hi, Mag. I think it is too risky to deliberately underprop your boat. If the possibillity exists to over-rev and destroy, Murphy says it will happen. Red sky at night. . . JB :)
mag	posted 07-07-2002 12:54 AM ET (US) JB, Thanks for the advice. I'll keep the prop I have. Maybe a smaller motor would eventually be a better solution? -mag
Peter	posted 07-07-2002 07:52 AM ET (US) Keep the prop you have. There is no harm in running at 3500. Generally, the less time you operate in the WOT range, the longer your engine will last. It's probably lasted this long because its hardly run at WOT.
Bigshot	posted 07-08-2002 01:59 PM ET (US) WOT is where you want the engine to run at WOT. You can run all day at 1000...2000....3500 etc but when that thropttle is smashed to the console and trimmed it should be at 4500-5500.