low water pressure on plane

[bassnut2]

97 pro sport bumble bee w/ 97 225 3 L merc...3" below the pad while on plane at 55 / 56 hunert rpms... wata pressa drops from 15 to 7 / 8 flucuating ....mota brand new rebuilt...fresh i tell ya... runs good...was runnin 5" below the pad wit good pressa...decided to raise mota a couple inches... thought ...hey 5" below the pad is a lot ....otta be able to come up on it a bit...pressa flucuates like krazy...i think i shoud be able to come up on the mota more but i need some input ....don't wont to burn up a new mota....

[EuropeanAM]

Fresh water pump with rebuild? Let's hope so.....

Your description indicates that there is AIR entering the water inlets at this speed. On your eariler-design gearcase, it's likely that it only has SIDE water intakes (no intakes at the nose of the gearcase).

This will LIMIT the height at which you can run the engine, as it's not possible to properly load the water inlets when they're near the water's surface.

I do NOT recommend plugging any of the side inlets on a gearcase that DOES NOT have low water pickups.

If this turns out to be the case (and you're going to try to run at this, or higher mounting heights), you would be wise to consider upgrading to a later-style gearcase with low water pickups (such as the Torquemaster, or at least a later ServiceMaster gearcase).

Another option would be to consider additional engine setback (placing the gearcase in cleaner water).

[bassnut2]

Thanks Don.... Yes new water pump...the motor is set back in cleaner water...however the top three holes are plugged on each side of the gearcase... I will remove those plugs and see what happens...water pressure was fine before the rebuild....so it is possible I may need to change the gearcase... How does the one I have compare to the... Hmmmm...lets say the torque master...Or would it be wise to have low water pick up added to my existing gearcase...

Thanks

[EuropeanAM]

If it were me.... I'd go to the later-style Torquemaster Gearcase, or at least a later style ServiceMaster gearcase (such as found on 2001-2006 3L Optimax or EFI models).

Avoid the "aftermarket" models.... IMHO, even a good used unit is a better choice.

[bassnut2]

I will start looking around for one...? Will my gears fit the later style gearcases so I can do a nice swap....

Thanks

[EuropeanAM]

That would depend on SPECIFICALLY which gearcase you were to choose.

Personally, I'd suggest a complete gearcase (and then sell the one you have currently).

[bassnut2]

That would be the easiest and smartest thing to do....

Thanks Don