Trying to squeeze out an extra 300-400rpm

[jprovencher80]

Hi, I recently dropped from a 23p to 21p tempest plus. Gets on plane quickly. The outboard is mounted on the second hole from the top. I can trim out to about 5300rpm on smooth water. If I try trim more the water pressure drops. She slips in turns when trimmed out and requires me to trim down to gain control on the turn. Sometimes I feel the prop blow out if I'm riding light chop. I feel like they engine wants to give me more but I'm not sure how to coax it out of her.

I have a manual jackplate I intend on installing.

And I better off....
1) live with 5300rpm
2) raise motor to get a few rpm and trim less
3) drop motor to up h20 pressure and gain trim

[pmgoffjr]

One aspirin at a time pards.
Put the plate on and THEN see what you've got. You will see a difference, but it's a wild guess how much.

[jprovencher80]

Am I best to start by trying to raise or lower the motor?

[jprovencher80]

Ok, will do!

[pmgoffjr]

Boat setup 101:
Take it too far and bring it back. You need to know what too high and what too low is.
Only way to find just right.

[Bassnailer]

If you need a little more height to get your RPMs up but don't have the water pressure, try the Mercury water scoops for the lower unit. I've ran them on several different boats and they perform quite well. Below is a link to an excellent detailed description of how to install them.

http://www.bbcboards.net/showthread.php?t=307560

[pmgoffjr]

15 is my low spot, some can live with 12. What are you thinking is too low?

[jprovencher80]

12 to 15 is the highest I see. When I continue to trim it starts bouncing between 5 and 10 rapidly. Impeller was replaced Sept of last year

[pmgoffjr]

You'll usually lose lift and speed before you lose water pressure. But that's not always a fact.
You NEED lift with that hull. If you're running flat, throwing a big tail and have really stiff steering, then you're too high on your motor. You should be able to run at full trim. But...you're running a sort of wildcard hull, and I've seen really big differences in transom angles.
Put your plate on, run it until you find the optimum setting, then and only then you might need to address your prop situation, there's pros that can work magic.

[HVAC86]

Did the boat used to run higher Rpms?

[jim maloney]

bone stone stock temptests normally run like crap

[jprovencher80]

No, boat never ran higher rpm. With a 23p tempest it ran up to 5k rpm. That's after a shop did new plugs / wires and some other work. Prior to that it made maybe 4500-4800 rpm

[HVAC86]

Something isn’t right. You should be able to turn a 21 nearly to the limiter. I’m wondering if you have a trim issue, like the rams not coming fully up, or possible fuel delivery issue.
or if throttle blades or opening fully.

[pmgoffjr]

He runs a tracker avalanche. It's a aluminum hull that is form molded, think of a big stamping machine. All that sounds really good until you put the human element into it.
I've rigged three of them and all three were completely different animals. First off the transom angle is all over the place, I had seven degrees difference between two boats, which completely changes the prop angle and how it runs. One needed negative trim spacers and one needed positive. The worst one had a three inch rocker three feet in front of the transom, that beast took electric trim tabs, negative trim spacers and a four blade prop before it calmed down enough to drive.

I can assure you he can't run the same prop height as a glass hull, the water coming off the bottom is pretty nasty.
From the vague descriptions, I'd drop the motor another inch and put a trophy on it that ran the right rpms and go fishing. Not at all a fun boat to try to tweak a few mph out of. At all.

[jprovencher80]

Is the outboard mounting hardware reusable? I ordered a new TH Marine bolt set to mount the jack plate to the transom. Can I reuse the motor hardware to attach the motor to the plate? Existing hardware is stainless/brass nylock

[pmgoffjr]

Yes.

[HVAC86]

I run a tracker 195, haha yes the hulls aren’t built consistent at all, nothing from tracker marine is. I had a trim Limit module go faulty and I lost 5 degrees positive trim until I unhooked it. Made an absolute huge difference in Rpms, speed and boat lift. Checking the hull for a hook or rocker would be something for sure I’d check, otherwise a man would chase him self tireless.