Should I be concerned

[Jimmy3]

I'm running a 150 Opti Pro XS, at the moment I'm still playing with PTP to optimize my performance. I'm pretty happy with where I'm at, may be able to squeeze out a little more but I'm running month long test to see where I'm happy with my normal use.

Is it normal for your water pressure to drop significantly for the first few seconds your boat gets on pad? Right before that last little bit of throttle that gets me completely on pad my water pressure is about 14 psi. Then I feel the boat lift, the RPMs come up, I give it the last little bit of trim and the water pressure drops to around 6 psi. This only last for about 2-3 seconds then the pressure begins to rise back up 9, 10, 12 psi for intervals of about 1 second each before jumping up to 16-18 psi, 13-14 psi when cornering without trimming. I'm contributing this to the turbulence comming off the hull causing an air pocket. I know that the minimum is 12 psi at WOT but unless I'm over 4" below pad this occurs so I'm assuming it's normal.

I guess ultimately I'm just looking for reassurance as I'm new to this and my discharge temp stays below 140° the whole time.

[AndrewM-Fishing]

When was the water pump/impeller changed last? If it's been a while I'd swap it out. 4" p2p seems a little low to be dropping that much psi.

[Jimmy3]

My current PTP is 3.5". The only way my water pressure won't drop momentarily when I get on pad is to have my PTP greater then 4".

Water pump and all seals are changed every year as annual maintenance. So, the water pump was changed about 4 months, or 30 hours, ago.

[Rip Bass]

You should wait for the boat to be planed out before trimming. It sounds like you are trimming as the hull is still climbing. You might be raising the water intakes too high at that time. But no,it’s not normal for the water pressure to drop while planing. Also,make sure you don’t have any obstructions in front of the lower unit,like a transducer.

[mdtritn21]

I start bumping the trim as soon the boat starts moving and keep bumping until it gets up then trim all the way. You can't just hit the trim button and hold it. You don't seem to have a water pressure problem since it calls for 1-5 lbs at idle and 12 at WOT but it sounds like you may have some wood or trash in the intakes or in the water pump housing.

[Jimmy3]

Checked that and back flushed the water system. It is HIGHLY possible that I'm trimming to soon, like I stated I'm new to driving a "high performance" boat. I tuck the motor all the way in bring the boat to plane, then bump the trim to the midwayish point, let it accelerate till it tops out at 43 or so, then bump up wait a second or two then bump up again, repeat till I'm in the 48-50 range. At this point I'm mostly trimmed out, maybe a bump or two away from max, I'll feel the hull "get light", RPMs climb at this point I add max throttle and bump trim to max. This is the moment I temporarily lose pressure, I can feel the boat seem to stabilize or settle, for lack of better words, my MPH climb as does my water pressure.

So the way I'm reading this I should wait a bit longer between my hull getting light and trimming out?

[mdtritn21]

You hit the gas normally wide open and bump the trim up as your moving keep bumping as the bow rises and when the bow drops you trim it up all you want. If you don't bump the trim up the boat won't rise up it will just stay bow down until you trim up.

[Jimmy3]

Ran the boat some today and waited longer before the final bump on the trim. The water pressure only fell to 13 before climbing back up. It seems as though my issue was just operator error. LOL

[mdtritn21]

It still should not fall because your speed is climbing. When the water pump was changed did you change the whole pump kit or just the impeller? Does your lower unit have intake holes in the nose?

[Jimmy3]

Whole pump kit

No to the low water pickups.

[lpugh]

Whole pump kit

No to the low water pickups.

Are you sure there are not 4 holes in the nose cone for water pick ups. May be wrong but I thought all pro xs motors had them
Anyway there are waters scoops availble to install on the lower that will direct more water to the side intake that work pretty well
Every Merc I have owned I have plugged the top four holes on the side intakes, has always allowed for higher mounting of the motor and sleight mods the the lower four.
Tap the 4 top holes with a 1/16 pipe tap and install pipe plugs that have recessed hex drive to tighten, The I use very small die grinder to inlarge the lowers a little and add a tear drop recess to the leading edge allowing the water to create more pressure on that opening, doesnt take much. Got to be smooth even transitions. Then paint the lower with high adhesion black primer, stays on better than anything and easy to touch up
This will allow for higher engine heights and better water pressure
Dont modifie the lowers if you do not have the skills required with the die grinder, the die grinder I am talking about is like a Dremel tool and uses 1/8 bits

Would be the perfect time to install a torque tab and mold it in as well, do not use rivits, machine counter sink brass screws only

[Jimmy3]

Absolutely positive I do not have low water pickups. My dealership said they never seen a pro xs without them as well, they contacted Mercury early on because I had issues with the motor running hot when it was new. Mercury's response was " The Motor with that serial number was not shipped with a lower unit that had low water pickups. We will not replace the lower unit with one that does without the customer purchasing a new unit." When I purchased the boat I didn't even know what a low water pickup was so I didn't look for that. Live and learn I guess. My dealership went to bat for me against Triton to get some gel coat repaired, they fought for almost a year before Triton agreed. I see no reason to not believe they tried against Mercury.

I'll look into the water scoops, didn't know they made such a thing.