Lund 14 DX and Merc 25 sluggish

[lgc]

I have a Lund 14 WC DX (400 lbs.) with a Merc 25 Bigfoot, and a 10 pitch/11.25 dia. alum prop. I estimate 750 lb. loaded with all gear plus 2 persons (about 1100 lb. total).
The boat is sluggish to get going and only gets to about 17mph and only 4200rpm. Seems to be plowing more than planing. I know the rpms are low but not sure how to correct it. Maybe less pitch or smaller diameter, trim the motor out one notch, or am I just too heavy? The other prop, 12 pitchX10.5 dia. got about the same results.

 

[Sea Rider]

Welcome to IBoats,

As a starter need to know the min-max wot rpm range for that motor factory stated to know how much under its max wot rpm the motor is currently revving at. Prop pitch, motor height, trim, load distribution, number of passengers also accounts for a bad water performance with such underpowered motor. If tach reads true wot rpm numbers definitely will need to go towards less pitch props to pull wot rpm towards its max which it's ideal.

Happy Boating​

 

[lgc]

Thanks Rider,
You covered most everything that I have considered and tried to correct. RPM rating for that motor is 5500-6000 wot and that's my concern. At 4200 rpm I am concerned that I am taxing the motor. However, the 10 pitch prop is already on the bottom end for that motor.

 

[Faztbullet]

You have more weight than HP and the bigfoot is hurting itdue to increased drag. Take the prop to a propeller shop and have them cut diameter down

 

[dwco5051]

You have more weight than HP and the bigfoot is hurting itdue to increased drag. Take the prop to a propeller shop and have them cut diameter down

I run an almost identical boat (Crestliner 14) with a Tohatsu 30 hp witch is a little more power and a 9.9 inch by 13 pitch prop for a top end of about 30 mph. With my old prop witch was a 12p it would over rev by 150 rpm with only my self on board. Just a guess but if your motor is working ok and trimmed right the larger diameter is what is causing your poor performance.

 

[Sea Rider]

I run an almost identical boat (Crestliner 14) with a Tohatsu 30 hp witch is a little more power and a 9.9 inch by 13 pitch prop for a top end of about 30 mph. With my old prop witch was a 12p it would over rev by 150 rpm with only my self on board.

Is the Crestliner boat being powered with a 2 or 4 stroke 30 HP Tohatsu motor ? I run a 2 stroke Tohatsu 30 HP on a 14 footer inflatable Sib, with 2 up and a spot on transom/motor height and neutral trim was only achieving 5000 wot revs on flat calm water cond with a factory delivered 3 blade 13 pitch prop, changed it to a 3 blade 11 pitch and increased the wot rpm to 5900/6000 rpm, now jumps on plane instantly with 2 up sitting way aft.

Happy Boating​

 

[Sea Rider]

To know :

What's the total weight of the boating package : Boat, + Merc 25, + 2 Souls on board,+ Fishing Gear ? Is it 1600 lbs (727 Kg) *

What's the Max HP and Passenger factory rated for the LuLund 14 WC DX ?

What's the min-max wot rpm range factory stated for the Merc 25 BF, is it a center console , tiller steering, with electrical or manual trim, transom bolt on motor ?

Happy Boating
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