Trim gauge question

[Butch Ammon]

Hey there....<br />I have a question about the Mercruiser trim gauge and how to adjust it (ie... the "needle" on the indicator on the dash is way off).<br /><br />See, you might remember my old (FREE!) boat or not:<br />

<br />1975 Glastex Sea Star, 17' trihull, Mercruiser 165 inline 6, on an old carpet bunk style black/white/primer(!) type of trailer. Hey, it was my dad's old boat, and is a great running boat!<br /><br />Anyway, last season, a buddy and I were fishing in the shallows, then went to move on to another location. The buddy was in the bow navigating for me, and I was ever-so-slowly, idling/moving in forward. There was a submerged tree stump up ahead and my buddy told me about it. I stopped, shifted to neutral and let us drift over the stump. Well, we had just barely enough forward momentum, that the bottom skeg biffed the submerged tree stump. It was enough to just lightly kick the outdrive up an inch or so, then the outdrive settled back down afterwards. No damage.... Everything is fine... No dings to the prop or skeg... No blown hydraulic lines... The boat still runs great, trims out fine, but the needle on the trim indicator is still way off. I figured last year it would settle itself with the constant up/down of the stern drive when trailering. This year, it's still way off. I have backed out the trim indicator/sender unit, and it helped, but not much. Is there a way to bleed the system, or another adjustment that I don't know about?<br /><br />Thanks... It's not really a big deal... The 165's trim still goes up and down without a problem and still runs great. I'd just like the needle on the dash to be aligned where it used to be.<br /><br />Butch A.

 

[Fishermark]

Re: Trim gauge question

When you say you "backed out the trim indicator/sender unit" - does that mean you turned the sender on the outdrive? That's where the gauge receives the signal - it is the black "cover" on the side of the outdrive at the hinge pin. One is for the trim limit, the other is for the gauge. I don't remember off hand which is which, but it should be marked. To adjust it you simply loosen the two screws holding it on and turn it one way or another.

 

[Butch Ammon]

Re: Trim gauge question

I don't have the sender on the outdrive. With my 165 Mercruiser, the trim sender is on the inside of the transom and the sender has a big threaded unit attached with two wires leading to the gauge on the dash.<br /><br />You can loosen the big locknut on the sender, then back out the threaded part, then tighten the locknut again. (if you take the whole thing off, you'll see a hydraulic ram or some type of plunger that pushes into the sender, which sends the signal to the gauge on the dash.)<br /><br />Butch A.

 

[Butch Ammon]

Re: Trim gauge question

Edit...<br /><br />Here is what I am talking about. I found a microfiche document on the internet on the 165 Mercruiser. See the link and look at part# 59 and part# 60 (which go into the main part# 52) and you'll know what I mean about the trim sender inside the transom.<br /> http://216.37.204.206/Shorts/mercruiser_oem/Mercruiser.asp?Type=13&SubType=113&A=18&B=12 <br /><br />Butch A.

 

[Fishermark]

Re: Trim gauge question

Sorry about that - I guess I didn't read your post closely enough! I'm afraid I can't help you with that one, but someone will chime in shortly I'm sure.

 

[rybad]

Re: Trim gauge question

(At least on my OMC guages) there is a screw adjuster on the back of the actual guage. If all you need to do is sync your guage with the actual position, that should do it. Just remove the guage from you guage panel, and you should see it. (again, thats how mine on my OMC are.. may be different for Merc.)<br /><br />-Dave

 

[achris]

Re: Trim gauge question

Originally posted by David 1995:<br /> (At least on my OMC guages) there is a screw adjuster on the back of the actual guage. If all you need to do is sync your guage with the actual position, that should do it. Just remove the guage from you guage panel, and you should see it. (again, thats how mine on my OMC are.. may be different for Merc.)<br /><br />-Dave

It is different for the Merc. The guage is fixed, no adjustment on it. The adjustment you are doing, moving the sender in and out on the threads, is the only 'adjustment' there is. Used to have an old 165 myself, which always suffered from trim gauge not working. Was a real PITA. You could try one thing. Take the sender right off its operating cylinder and check that the cylinder is moving the full travel. Other that that, I don't know any ways beyond what you're doing.<br /><br />Chris.

 

[paulrfrancisco]

Re: Trim gauge question

here is a link on how to adjust the limit switch and the gauge sending unit...<br /><br />Good luck.<br /><br />Paul<br /><br /> http://www.mercstuff.com/trim_limit.htm

 

[achris]

Re: Trim gauge question

Originally posted by Paul032562:<br /> here is a link on how to adjust the limit switch and the gauge sending unit...<br /><br />Good luck.<br /><br />Paul<br /><br /> http://www.mercstuff.com/trim_limit.htm

That's for the rotary sender and limit switch. This pre-dates those.

 

[paulrfrancisco]

Re: Trim gauge question

Thanks, I wasn't aware that they were different in 1975.<br /><br />Paul

 

[rodbolt]

Re: Trim gauge question

hello<br /> its still a potentiometer type sender. all the sender is is a variable resistor that converts a known mecanical value to a known electrical resistance and feeds it to a balanced coil type gauge. it will work mounted or not by key on and moving the plunger in and out.(of the electrical sender) by memory I cannot remember the bleeding procedure for it. the plunger from the position sender pushes the plunger in the electrical sender. the plunger in the electrical sender is spring loaded, best memory serves, to follow the hydraulic plunger from the hydraulic sender. without going to hunt for my antique manual I cant help much. you can attempt a test by using an ohm meter on the electrical sender while pushing in and out on the plunger inside it. I cant remember the bleeding procedures or the hudraulic test procedure. if I get a chance Ill look about for it over the weekend. was an odd system that was not very popular.

 

[74Silverline]

Re: Trim gauge question

Yah, that would be great if some info on how to adjust that trim sending unit was available. I have the same setup and my trim gauge is also off. The gauge won't show movement till the drive is half down or up. It would be nice if a guy could get that fixed. I've searched high and low for the info on that sending unit and I've only come up empty.<br />Thanks,<br />74silverline

 

[Butch Ammon]

Re: Trim gauge question

I have an idea with my trim gauge (as crazy as this sounds)... <br /><br />I am going to try something nutty - I am going to raise the stern drive all the way up. Then I'll loosen up the trim sender locknut thing, and screw it ALL THE WAY IN to the hydraulic ram/trim component. Then, carefully, I'll hit the down buttons and lower the stern drive all the way down. If it goes all the way down, then the hydraulic trim sender has a self-adjusting valve built inside and won't cause the ram to bottom out in the trim indicator/sender unit. If this works, then it will be okay, and will hopefully reset. Then, I'll simply unscrew the locknut and sending unit, and unscrew it back out a ways, then raise/lower the stern drive again and check the reading on the gauge. I've read through an old Mercruiser manual and there is no easy way to adjust anything, except getting another person involved to help bleed the system.<br /><br />Butch A.

 

[Butch Ammon]

Re: Trim gauge question

Update: Over the weekend, I tested the trim sender assembly on my old Mercruiser 165. Up, down, up, down, up, down... Threaded trim sender screwed all the way in... Threaded trim sender hanging on by a few threads...<br /><br />Didn't matter... The trim gauge is still wacky! Oh well... there is a way to bleed the system, but I don't have time to mess with it (and make a mess with hydraulic fluid in the stern). The 165 is running great, the trim is working great, so it might be more trouble than it is worth.<br /><br />Butch A.