24p fury

[coachallen]

I have a 200hp efi with a 24p fury. My hole shot is okay and when I am running my water pressure is at 30. until I start to trim up. I am running 64/65 mph with 2 people at 5800rpm's.. My question is will raising the motor hurt top end speed? Should I raise the motor up more? My boat is a 18'8 cobra...

[lpugh]

I suspect you are to high right now, should not lose water pressure when trimmed up, what is the pressure when trimmed for maximum speed, also look at the pressure trimmed up when turning both directions as there be be even more loss
Does the lower unit have 8 water intake holes in the side of the case and none in the nose cone, if this is how your gear case looks there are mods that can be done to lift the motor more and maintain good pressure
The top 4 holes can be plugged by drilling ang taping to 1/16 pipe threads and installing plugs in those holes. When I have in the past I also Reshape and enlarge the lower 4 holes. This should only be done by some one that has good skills with a die grinder and understand how to reshape that area to increase water flow
The draw back is it can allow for larger objects to get pulled into the water pump, These are minor changes teardrop shaped to allow the water to turn into the case a little faster. Without a good understanding of how to do this you can easily ruin the the case
There are water scoops available to achieve similar results that is a much safer way to increase the flow, not as good as what mentioned above, but most can install them with little experience

[coachallen]

Once I trim up and at 65mph I am at 13 to 15 on the water pressure.. I lose a little when I turn either side. I was just wondering if raising the motor up on a jackplate would hurt my top end speed..

[lpugh]

John for best performance you must find what is to high and what to low for your setup. Use you gps to monito speeds and a digital tach or smartcraft for rpm. at top speed try to find the best trim position for the highest speed, note the water pressure, rpm and speed, Raise the motor 1/4 in and repeat, take notes every change you make. You will notice that at some point the speed does not increase and/or the rpm goes up with no increase in speed. You now found what is to high, drop back down 1/4 in. Do this on the same with a normal load that you carry most of the time. If you are getting improvements and water pressure drops, consider the steps above so the motor can be lifted a little higher

I think your Cobra will benefit from higher mounting, but most like will have to modify the water intakes or go to a different lower unit, 15 psi trimmed up, I would be concerned with

[coachallen]

I was told my psi should be around 12 to 15 when trmiied up. Heck I have to trim the motor half way up before I start getting to 15 psi. Most of the time it is at 30 unti trimming up.

[lpugh]

That is a warning you are in borderline danger area, Say you running hard at 15 psi and wakes or boat traffic requires your full attention, you start turning and psi drops to 5 suddenly or less, you could size a motor in 15 seconds, Worst case scenario but it could happen, I would never except a 15 psi drop in order to run the motor a little higher. Consider making some changes to correct that, at the least add the scoops, the very best is a lower with nose cone water intakes and plug the top 3 or 4 side ones
Until you experience how fast these motor can seize when under load it is hard to grasp
15 is safe as long as it there all the time under all conditions, no room for error though

[mdtritn21]

Water pressure on your motor should be 1.5 to 5 lbs at idle and 12 minimum at WOT trimmed out. If it going under 12 lbs when turning put the Mercury high speed water scoops on it to stabilize the water pressure when turning. If your not getting an over heat alarm it's getting enough water pressure to cool it down at WOT.