Trim-Indicators and -senders

[Hans-Joachim Sellner]

Hope that Trim-Indicators and -senders stand for Electronics too, so it
will be the right group here for my question:
Mercruiser's trim-sender is a potentiometric one with a down-resistance
of 10 Ohms and an up-resistance of 167 Ohms. Does anybody know, whether
this 157 Ohm-difference is a fraction of a built-in standard-poti with a
full-angle of 270°? If it is a fraction only, then the max. poti-value
over a range of 270° should be about 850 Ohm, because trim/tilt (max) is
about 50°. Or is the built-in poti a special one with a max. angle of
the said 50° + some additional degrees for "mechanical" security?

Appreciating any contribution,

bye, Hajo

 

[bowgus]

The trim pot (alpha, starboard side) is very very easy to remove, degrease
, disassemble, reassemble and reinstall. I've done it but was not looking
at the range (I'm thinking it was not 270, more like 90-120). On mine, that
6 (8?) sided piece of &^%$# plastic insert had broken and therefore was
slipping. Maybe just pop it off and take a look for yourself ?

 

[Hans-Joachim Sellner]

The trim pot (alpha, starboard side) is very very easy to remove, degrease
, disassemble, reassemble and reinstall. I've done it but was not looking
at the range (I'm thinking it was not 270, more like 90-120). On mine, that
6 (8?) sided piece of &^%$# plastic insert had broken and therefore was
slipping. Maybe just pop it off and take a look for yourself ?

I don't run Mercruiser but BMW, I'm only interested in the technic of
this device, because my BMW-trim-sender is faulty with no chance to get
a spare part. So I'm looking what the competitors do ;-). Perhaps I can
rebuild it.
Thanks and bye, Hajo

 

[Eike Lantzsch, ZP6CGE]

I don't run Mercruiser but BMW, I'm only interested in the technic of
this device, because my BMW-trim-sender is faulty with no chance to get
a spare part. So I'm looking what the competitors do ;-). Perhaps I can
rebuild it.
Thanks and bye, Hajo

Hajo:

On the Mercury Bravo Drive the sensor does not even have 90° angle
AFAIR. You can turn the sender around all 360° but the actual angle
for measuring is far smaller. I cannot look right now and the
installation we did was 1/2a year ago.
270° seems a bit exaggerated for a trim sensor. Is that
really necessary? Not even rudder angle indicators need 270°.
The Mercury Sender is not an ordinary pot. It is wire wound.
It is not very accurate but accurate enough. You can't use carbon
pots in vehicles or boats.

Maybe you might want to look for "VDO Oceanline Trim
Indicator" as well. You can download the information here:
http://www2.vdo.com/vdo/end_consumer/ec_download_and_fza=_and_
childid=872_and_id=87200000.aspx
(Mind the linefeed after the "_" in the URL)
The distributor for VDO is MARX-Navigationssysteme in Hamburg,
Germany. They have a website too: http://www.marx-technik.de/
You might get a better price there than with your boat dealer.
We bought directly from Marx. They also have a good repair service.
Worked with them already in the 70s.

The VDO Trim Gauge is made for Mercury Trim Senders so it might
work for you to install the Mercury Sender. I doubt that the
VDO Sender is made by VDO. It does not appear in their catalogue.

Uh - you know all this already, I guess.
I saw your posts here - I realized a little late - it was you,
wasn't it?
http://www.dk-forenserver.de/boote/showthread.php?s=0eb5c2aba
78c29d942145a5d2088141b&p=45514#post45514

Wish you luck.
Kind regards, Eike from Paraguay

 

[Hans-Joachim Sellner]

Hajo:

On the Mercury Bravo Drive the sensor does not even have 90° angle
AFAIR. You can turn the sender around all 360° but the actual angle
for measuring is far smaller. I cannot look right now and the
installation we did was 1/2a year ago.
270° seems a bit exaggerated for a trim sensor. Is that
really necessary? Not even rudder angle indicators need 270°.
The Mercury Sender is not an ordinary pot. It is wire wound.
It is not very accurate but accurate enough. You can't use carbon
pots in vehicles or boats.

Maybe you might want to look for "VDO Oceanline Trim
Indicator" as well. You can download the information here:
http://www2.vdo.com/vdo/end_consumer/ec_download_and_fza=_and_
childid=872_and_id=87200000.aspx
(Mind the linefeed after the "_" in the URL)
The distributor for VDO is MARX-Navigationssysteme in Hamburg,
Germany. They have a website too: http://www.marx-technik.de/
You might get a better price there than with your boat dealer.
We bought directly from Marx. They also have a good repair service.
Worked with them already in the 70s.

The VDO Trim Gauge is made for Mercury Trim Senders so it might
work for you to install the Mercury Sender. I doubt that the
VDO Sender is made by VDO. It does not appear in their catalogue.

Uh - you know all this already, I guess.
I saw your posts here - I realized a little late - it was you,
wasn't it?
http://www.dk-forenserver.de/boote/showthread.php?s=0eb5c2aba
78c29d942145a5d2088141b&p=45514#post45514

Wish you luck.
Kind regards, Eike from Paraguay

Many thanks, that's really more than I expected!
Well, it's true, I don't need a potentiometer with a working-range of
270°. But commercial pots have this range only. I need a small fraction
of this, about 50 degree, as I wrote above. It's worth to know that
Mercruiser takes a wire wound pot, but on the other side I really wonder
that it turns all around. The mercruiser pot then should have 1,2KOhms
over 360 degree, provided they need a working range of 10 to 167 Ohms
(53 degree).
Anyway, I now know what's important: Wire wound, 360 degree (270 degree
is possible too, you must not turn it all around), and Mercruiser
measures on a small resistance area (fraction of one turn).

So far, thanks a lot!

Bye, Hajo

 

[WaIIy]

The Mercury Sender is not an ordinary pot. It is wire wound.
It is not very accurate but accurate enough. You can't use carbon
pots in vehicles or boats.

The discs I replaced in my Alpha Ones sure looked like a round piece of
plastic with a carbon insert.

I could be wrong, but they weren't wire wound as far as I could tell.

 

[Eike Lantzsch, ZP6CGE]

Many thanks, that's really more than I expected!
Well, it's true, I don't need a potentiometer with a working-range of
270°. But commercial pots have this range only. I need a small fraction
of this, about 50 degree, as I wrote above. It's worth to know that
Mercruiser takes a wire wound pot, but on the other side I really wonder
that it turns all around. The mercruiser pot then should have 1,2KOhms
over 360 degree, provided they need a working range of 10 to 167 Ohms
(53 degree).
Anyway, I now know what's important: Wire wound, 360 degree (270 degree
is possible too, you must not turn it all around), and Mercruiser
measures on a small resistance area (fraction of one turn).

So far, thanks a lot!

Bye, Hajo

Hayo:
No no! The Mercury pot does not have a resistance area of 360°. The
area of resistance is only about less than 90° (maybe 60°). You just
CAN turn the sender mechanically for 360°. Most of this angle has
no contact to the wire wound resistor at all - it just goes open when
out of its range.
It is a little bitch to adjust sometimes too, especially if you have
two Bravo Drives and want to have the gauges indicate exactly the
same with the same trim on both sides.
I was looking for a picture of the sender but couldn't find one.
It is a round plastic tablet about 2" in diameter. It has two long
holes on the perimeter for adjustment. The actuator is a dented
shaft which fits into the joint (or knuckle or articulation) of the
Z-drive. If you take it off you will have some fun to find the right
point of resistance again when you try to put it back in. An ohmmeter
helps a lot. Before you remove the sender be sure to make a note
about where to place the plastic tye-wrap again to hold off the wires
of the sender from the yoke of the Z-drive. Otherwise the wires will
be hurt or even cut when the drive is tilted or inclined and THAT is
really hard to fix.
In another post the repair of the sender was mentioned. Are you shure
that the sender you have is beyond repair? It might be that there is
just a cut wire. Copper becomes stiffer with every bend and
eventually breaks. The sender is such a simple contraption that it
might only need cleaning and some tiny touch of grease.

cheers, Eike

 

[Eike Lantzsch, ZP6CGE]

The discs I replaced in my Alpha Ones sure looked like a round piece of
plastic with a carbon insert.

I could be wrong, but they weren't wire wound as far as I could tell.

There might be different types out there. I must say that I didn't
open the sensors but deducted "wire wound" from the "steppy"
characteristic of the resistance of the senders we installed. Ours
may be older - I don't know.
If the sensors are carbon and not conductive plastic or cermet then
I'm not surprized that the senders break. Wire wound would cost a few
cents more but they would never break.
Well - I saw bad engineering before - sigh ...

Then here is a warning: When cleaning carbon pots be very choosy
about the liquid you use. The wrong one (even contact cleaner) may
destroy the resistive part or the metal cover for the contacts.

Kind regards, Eike

 

[Hans-Joachim Sellner]

Hayo:
No no! The Mercury pot does not have a resistance area of 360°. The
area of resistance is only about less than 90° (maybe 60°). You just
CAN turn the sender mechanically for 360°. Most of this angle has
no contact to the wire wound resistor at all - it just goes open when
out of its range.
It is a little bitch to adjust sometimes too, especially if you have
two Bravo Drives and want to have the gauges indicate exactly the
same with the same trim on both sides.
I was looking for a picture of the sender but couldn't find one.
It is a round plastic tablet about 2" in diameter. It has two long
holes on the perimeter for adjustment. The actuator is a dented
shaft which fits into the joint (or knuckle or articulation) of the
Z-drive. If you take it off you will have some fun to find the right
point of resistance again when you try to put it back in. An ohmmeter
helps a lot. Before you remove the sender be sure to make a note
about where to place the plastic tye-wrap again to hold off the wires
of the sender from the yoke of the Z-drive. Otherwise the wires will
be hurt or even cut when the drive is tilted or inclined and THAT is
really hard to fix.
In another post the repair of the sender was mentioned. Are you shure
that the sender you have is beyond repair? It might be that there is
just a cut wire. Copper becomes stiffer with every bend and
eventually breaks. The sender is such a simple contraption that it
might only need cleaning and some tiny touch of grease.

cheers, Eike

O.k., I understand, it's a special pot which has a conductive region of
about 60 degrees over a circular movement of 360 degrees.
Well, I'll start some experiments with a Teleflex gauge and a
pot/resistor combination to simulate the effect of Mercruisers pot.
My trim-sender is (better was) an inductive type made by VDO. It's built
into one of the bolts which make the drive move up and down. It's
completely destroyed and as I believe rebuilding is a mess, I try a
technic which is simple to integrate into the bolt. And that's a pot!

Thanks a lot!

Bye, Hajo

 

[WaIIy]

Then here is a warning: When cleaning carbon pots be very choosy
about the liquid you use. The wrong one (even contact cleaner) may
destroy the resistive part or the metal cover for the contacts.

That's interesting. I replaced one on a 1994 Alpha One and the old disc
looked perfect, but my gauge needle would be very jumpy. I replace the
disc (about $12.00 US) and everything was fine. I'm not familiar with
the newer sending units for I/O tilt, but the older ones are a very
cheesey design. Many times, the wires coming out of the sender chaf or
corrode and it's not cheap to replace the little harness.
Of course, I cobbled up a decent repair without replacing all the wires.