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Trim/Tilt problems 218 LS

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I have a 2004 218 LS that I bought new has 180 hrs of fresh water time on it. The trim/tilt works fine but the gauge is not working. This is where the problem comes in. When the trim button is pressed while the boat is running the voltage gauge and fuel gauge drop to the off position and the radio cuts outs.


Things I have tried so far:




1) The two batteries are new but I pulled them out and had them tested and both are good with a full charge.

2) Put a volt meter on the batteries with the boat off and am reading 12.8 volts

3) Put a volt meter on the batteries with the boat running and am reading 14.8 volts.

4) Put a volt meter on the batteries with the boat running and pressed the trim button and am reading 13.5 volts.

5) Disconnected the radio power and ground pressed the trim button and gauges react the same. (drop to off position)

6) Disconnected both batteries with boat running and pressed the trim button and gauges react the same.



This eliminated the batteries and the radio as the cause. I am wondering if it could be a short in the trim sending unit. If so how can I disconnect it to see if the gauges drop or not? Any suggestion for a cause would be greatly appreciated.



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I had been waiting to see if someone else with a much better understanding would respond. No-one has, so here a few ideas to hopefully chase down your problem.


To answer your specific question, I don't know how you can check the trim sending unit in service. If you disconnect it, the pump won't work. The pumps used on mercruiser only have 3 wires entering (up, down and neutral) so I'm guessing the monitoring of the position of your trim is handled someplace other than the pump motor itself. Most likely will be the ECM (engine control manual) of which I know nothing about except all your instrumentation comes from / goes through there.


You don't say if it is a mercruiser or volvo. I have mercruiser but assume volvo would be similar.


If you purchased the boat new, you should have received an installation manual for your engines. (I'm not sure if you can find a copy somewhere but if it helps I have the one for the Mercruiser 350MAG-MPI - let me know if you need a copy). I assume the trim pump assembly/s would be pretty similar across most engine variants. (See attached pics).


I do have some suggestions that might be helpful. If they don't work, I'm guessing the only way you will resolve your problems is to get the ECM checked out. Some ECM's also store fault codes which can be diagnostically checked by someone with the correct equipment (not sure about year models in 2004)


Many strange problems in DC systems can come from a loose wire or two.

First item should be to make sure all the neutral wires in and around the trim pump assembly are clean, free from corossion and tight.

Next, make sure all the neutrals in and around your engine block are similarly clean / tight. Check the mounting of the ECM and its neutral wire connection into the 'box'. There might also be a 'tie' wire to the engine block to check as well.

Finally it would also be a good idea to check battery neutral and main connection to engine mount.


Another check to do is to understand what voltages happen at the rear of your gauges.

Does the 12V supply completely disappear? or does it drop to a lower value which the falls below the guage threshold?

When testing this, don't use the gauge nuetral wire connected to the guage itself, pick another neutral - say your cigarette lighter.


I don't think you have a short in your pump motor otherwise the fuses would be blowing.


It may also be possible to have a short in your instrumentation wiring harness but i think this would be less likely as more than 1 gauge is being affected.


Finally, I am intrigued by your item #6. If you disconnected the engine battery, trim would go dead, everything would go dead and your motor would have stopped (if it was running). What batteries are you referring to?


Good luck

trim assembly.pdf

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I had a similar problem on my 218 LS with a Volvo Unit beginning of the season. I thought my trim button was bad but it turned out to be corrosion on the connectors in the starboard gunnel. Took apart cleaned and reassembled with dielectric grease. No more issues....

Good Luck

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