top end issues

marchelg

Recruit
Joined
Dec 4, 2017
Messages
3
I have a 2017 Lund 1875 with a 115 MERC PRO XS. With the motor down it will top out at 4300 RPMs and 38 MPH. If I trim the motor up I can get up to top RPMs but my top end still is only 38. Anyone else have the problem. Dealer and Lund says that is just the way it is
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
Speed by gps or water pressure Speedo? Does the bow rise as the engine is trimmed out/up? What prop are you running?
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
That issue is due because prop blades are not getting top water thrust when OB is trimmed up or even down. Prop blades should rev perpendicular to water level to get the max out of them. It's like swimming with open fingers..Optimum OB/transom height also plays its role for top prop thrust doing its homework right.

Happy Boating
 
Last edited:

porscheguy

Chief Petty Officer
Joined
Jan 17, 2013
Messages
441
What is ?top rpm?? Mercury puts the WOT range on this engine at 5300-6300rpm.

Do you have a command thrust gearcase? What is your gear ratio?

What hole is your o/b mounted on? Engine height is important on o/bs.
 
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