boat really hard to plane

[trevin11]

I have a 1992 nitro bass boat 18ft with a 1988 mercury 150 HP with a power tech 23 pitch prop I got used a month ago when I try to plane out my motor has to be all the way down like where the motor upper cowling like in a 45 degree angle when I hammer on it my throttle is all the way full and it goes to about 3000rpm and stays there about 4 seconds then the motor gets power and then it will come up it takes about 20 seconds to plane out total and when up on plane it runs 5800rpm at 55 MPH is there any thing to worry about with this

 

[coastalrichard]

Re: boat really hard to plane

For a good hole shot, the motor needs to "spool up" quickly to get the rpms needed to plane out. It's likely that the 23p is a bit to much. You should determine the rpm range for your motor and then prop it so that it hits the upper end of the range at WOT. It is not unusual for boat owners to have different props for different boating purposes (ie cruising around vs pulling skiers/wakeboarders). That rig, when propped properly, should plane out in a few seconds. Good Luck!

 

[CharlieB]

Re: boat really hard to plane

5800 at WOT should be a good number.

If the carb idle circuits are very slightly restricted that can reduce acceleration. A simple test is to just 'bump' the enrichener/choke while attempting to get on plane. if the momentary additional fuel improves power then it is a safe bet that it is time to clean the carbs, and possibly rebuild the fuel pump (cheap insurance).

Another angle, is your prop 'vented', does it have three holes in the side of the center barrel, one each just behind the leading edge of each blade? Vented props allow a certain amount of additional 'slip' and allow the motor to gain RPM very rapidly, almost makeing the boat feel like it 'jumps' up out of the water. Once the boat noses over, water flow across the holes 'seals, the blades get a full bite on the water, RPM drops as if you shifted into 2nd gear, and the boat continues to accelerate to WOT RPM.

A vented prop can make a world of difference, but outboards have run perfectly fine without them for next to forever.

Just for the the peace of mind, check compression and test spark on each cyl to rule out any obvious problem, follow that with a DVA test of the stator high speed windings to ensure the stator is well within specs. Once you make sure the basics are fine, again rpeat the enrighener 'bump' test, when that improves power, even for a few heatbeats, then order carb kits and start cleaning.