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Author Topic:   RPM drop on plane

AZdave posted 08-30-2010 08:14 PM ET (US)
Today as I accelerated my 18 Outrage onto plane I noticed a drop of as much as 300-500 RPM within a second or two of planing out. The impression was that the boat had shifted into overdrive. Here are the specifics: 135 Mercury trimmed all the way down with a four blade stainless prop with a 19" pitch. Less than one foot waves, two adults and a third of a tank of fuel. Thanks for your thoughts.
Tohsgib posted 08-30-2010 10:58 PM ET (US)
Slip then grip...why are you trimmed all the way down?
AZdave posted 08-30-2010 11:57 PM ET (US)
I've been told to trim down to get on plane quickly, then trim up for neutral steering and top speed from the GPS. Do I need to rethink that?
Tohsgib posted 08-31-2010 10:28 AM ET (US)
Well only if you are waterskiing or desperatly need a great holeshot everytime. The more you mash down the throttle from a start the more stress you put on your lower unit and transom. With an 18 you should be able to leave it set and get up on plane easily...try what you like but no need to do jackrabbit starts EVERY time.
AZdave posted 08-31-2010 06:59 PM ET (US)
Thanks Nick, that makes sense. I almost never do full throttle starts, and that's probably the reason I never noticed the transition from slip to grip before. I grew up with small fishing boats and smaller motors, so I'm weak on the common sense, almost cultural, aspects of power boating.
Tohsgib posted 08-31-2010 10:37 PM ET (US)
Mark your prop and hub to see if it is slipping. Only takes one holeshot to see.

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Author	Topic: RPM drop on plane
AZdave	posted 08-30-2010 08:14 PM ET (US) Today as I accelerated my 18 Outrage onto plane I noticed a drop of as much as 300-500 RPM within a second or two of planing out. The impression was that the boat had shifted into overdrive. Here are the specifics: 135 Mercury trimmed all the way down with a four blade stainless prop with a 19" pitch. Less than one foot waves, two adults and a third of a tank of fuel. Thanks for your thoughts.
Tohsgib	posted 08-30-2010 10:58 PM ET (US) Slip then grip...why are you trimmed all the way down?
AZdave	posted 08-30-2010 11:57 PM ET (US) I've been told to trim down to get on plane quickly, then trim up for neutral steering and top speed from the GPS. Do I need to rethink that?
Tohsgib	posted 08-31-2010 10:28 AM ET (US) Well only if you are waterskiing or desperatly need a great holeshot everytime. The more you mash down the throttle from a start the more stress you put on your lower unit and transom. With an 18 you should be able to leave it set and get up on plane easily...try what you like but no need to do jackrabbit starts EVERY time.
AZdave	posted 08-31-2010 06:59 PM ET (US) Thanks Nick, that makes sense. I almost never do full throttle starts, and that's probably the reason I never noticed the transition from slip to grip before. I grew up with small fishing boats and smaller motors, so I'm weak on the common sense, almost cultural, aspects of power boating.
Tohsgib	posted 08-31-2010 10:37 PM ET (US) Mark your prop and hub to see if it is slipping. Only takes one holeshot to see.