Mysterious tilt trim issue

[2000Charger]

Hey guys I’m having some weird issues that I’ve been dealing with for a few years and starting to lose my patience with finding a solution. I have a 2000 charger bass boat with a 200hp ox66 max on it. To get my optimal speed and rpms out of the motor I used to watch my water pressure gauge while trimming up, as soon as pressure began to fall off I would bump the trim down a click and that’s where my boat would perform the best. I would get 5800-5900 rpms out of it. Well, I ran aground on takeoff a few years ago and ended up replacing the lower unit. I removed the lower unit myself and replaced it myself (I have a mechanical background) the lower unit was replaced with an exact match and same gear ratio, the prop was repaired and I even bought a matching spare. Now here’s my problem…ever since this happened I can no longer get my motor to trim up high enough to get the pressure to drop off….it gets to a certain point and just stops even if I continue to hold the button down. I can only get about 5200-5300 rpms out of it now because of this and have lost about 6mph. Before this happened I could run the motor out of the water if I really wanted to but now it seems that once it has a load on it, it will only go so high…I should also add that it works perfectly normal in any other situation. I have changed the trim fluid, I have removed the lower unit to replace the impeller since, and I know this motor doesn’t have a trim limit. I’m stumped, any help would be much appreciated. Thanks.

[TownsendsFJR1300]

Is the trim tab adjusted the same (correctly) as before?

With hydraulic steering, a mis-adjusted tab would be hard to "feel".



From my F150 shop manual.

Capture.JPG

[2000Charger]

Yes it’s the same, it’s like the button stops working at a certain point….it just won’t trim up anymore after a certain point.

[DennisG01]

Boy, that's a good one. You're right - there is no "trim limit" stop on those engines. Just replacing the gear case obviously isn't the issue - heck, doing so doesn't even require messing with the trim sender on the bracket. Did you add a different gauge, or do any other add-ons that could explain this?

[2000Charger]

Nope nothing else changed

[DennisG01]

Just to clarify, it sounds like it is "electrically" stopping? Like it's hitting a switch and turning off?

You mentioned it happens normally in all other situations... does that include at, say, 1/2 or 3/4 throttle?

Do this if you feel comfortable... but once it hits this theoretical "limit"... can you use the tilt button on the side of the engine to raise it further? You'd just need a quick verification on this. Probably best to have a friend do that while you drive.

[2000Charger]

I could try that, if just have to find a friend that has enough balls to do it lol I’ve only noticed it at 3/4 to full throttle I could back it down a bit and see what happens also….what I meant in my original post is that it acts normal in all other situations except under full load.

[Bluefish]

The unit has a pressure relief built in to kick motor up to minimize damage when something is struck obviously didn’t work to well for you. It is a spring-loaded ball bearing used to dump fluid when the max pressure is reached. You could try releasing the manual valve located on the side of the unit and left the motor up and down and see if that seats the relief valve. But by your description it sounds like you have a mechanical bind, that and along with trying to rise it under load is exceeding the max pressure. Pull the pin and left the motor up and down should go very easy. How is the grease in the tilt tube?

[2000Charger]

This is more along the lines of what I what thinking, some sort of damaged relief valve or something…but unfortunately I’ve ran that manual relief at least 20 times in the past couple years trying to screw with it with no luck…would it be possible the trim motor is getting weak and can’t work correctly under full load anymore? Still seems weird it would all of the sudden start acting like this and stay unchanged for a few years.

[99yam40]

I would monitor the amps to the T&T motor to see if it still runs when this is happening.
A DC clamp on Ammeter clipped around one of the wires to the motor will tell if the T&T motor is running and what load it is running at.

I thought I read before that limits on the T&T could be set to keep from damaging parts on some rigs if they came up too far, but I do not remember on what motors or how that worked

[DennisG01]

This is more along the lines of what I what thinking, some sort of damaged relief valve or something…but unfortunately I’ve ran that manual relief at least 20 times in the past couple years trying to screw with it with no luck…would it be possible the trim motor is getting weak and can’t work correctly under full load anymore? Still seems weird it would all of the sudden start acting like this and stay unchanged for a few years.

Wait, I was under the impression that the motor was stopping like someone flipping a switch? Not that it was still TRYING to go up (still making noise)? That's two totally different things. That's why I asking for clarification above - but since you didn't correct me, I assumed it was still an electrical thing.

[2000Charger]

No I don’t really have any inclination to believe that it’s still “trying” to work, if it is I can’t hear it while at that rpm range…as far as I can tell it gets to a certain height and then just stops raising.

[DennisG01]

No I don’t really have any inclination to believe that it’s still “trying” to work, if it is I can’t hear it while at that rpm range…as far as I can tell it gets to a certain height and then just stops raising.

OK, that would be a good thing to verify, then. Maybe a younger friend with younger ears can get their head closer and take notice to if the trim motor noise stops, or not. It would certainly make more sense, though, if it is jamming up as opposed to electrically stopping.

[99yam40]

OK, that would be a good thing to verify, then. Maybe a younger friend with younger ears can get their head closer and take notice to if the trim motor noise stops, or not. It would certainly make more sense, though, if it is jamming up as opposed to electrically stopping.

this is why I posted measuring/monitoring T&T amps,
WOT motor noise makes it hard to hear a small electric motor
not to mention the noise from wind and water striking the hull