Merc offshore trim pump

[Oliver.Ashworth]

Hi All,

I'm looking for a way of testing a merc trim pump to see if it is holding pressure correctly... I spent most of last season replacing the seals in the trim ram (offshore type) which seemed to stop the engine trimming in under load/ when parked up on the trailer overnight temporarily (for a couple of weeks) but I'm starting to think this was just a coincidence...? There is no pitting on the trim ram/ internal wall of the cylinder and none of the seals have had any visible damage before replacement. The oil in the cylinder is also free of water/air when I drain it down.

So....... is there any way of testing the trim pump to see if it is holding pressure? It is one of the old versions with the steel reservoir.

Cheers,

Ollie

[Techteam]

Test gauge setup from Merc or you can make your own with some gauges and ballfix valves. I will ask though, your sure you have up and down the right way hydraulically and electrically. What I mean by that is the up and down check valve pressures are different, so if you fit up to down the check valve will not hold the engine up and it will slowly push back in from the thrust of the propeller or weight of the engine while towing etc. I have fixed this many times before especially when someone has wired the boat themselves taken a guess at the hydraulic pipes and then instead of wiring green and blue correctly have just connected the trim switch so that it masks the problem. Seems to work ok but not correct.

[Oliver.Ashworth]

I believe the hydraulic hoses are connected correctly as the end fittings are all different i.e. different thread size/pitch, male/female etc. so it can only be connected up one way.... I hadn't realised the issue with the wiring, as you guessed I wired it up in a way that 'appeared' to be correct... so this could well be the problem. The trim hasn't always given me problems (It worked fine for around 6 months after I wired it up) however it seems like a good thing to check before going any further. Do you have a wiring diagram for the trim pump?

Thanks for your help,

Ollie

[Oliver.Ashworth]

Is it the polarity of the wiring that causes the issue?

[maz928]

This is the mercury test kit

[OCRDA]

Originally Posted by Oliver.Ashworth

I believe the hydraulic hoses are connected correctly as the end fittings are all different i.e. different thread size/pitch, male/female etc. so it can only be connected up one way.... I hadn't realised the issue with the wiring, as you guessed I wired it up in a way that 'appeared' to be correct... so this could well be the problem. The trim hasn't always given me problems (It worked fine for around 6 months after I wired it up) however it seems like a good thing to check before going any further. Do you have a wiring diagram for the trim pump?

Thanks for your help,

Ollie

Blue = Up Or Blue = Sky
Green = Down Green = Grass

[Oliver.Ashworth]

Cheers Bob, I'll check it out tomorrow

[Oliver.Ashworth]

Originally Posted by maz928

This is the mercury test kit

Looks pretty straightforward, if the wiring's correct I guess I could rig something up with a hydraulic pressure gauge and some adapters on the end of each hose to see if the pump's holding pressure or not.

Thanks for the help

[Sam1cats]

Just in case I have a high-pressure trim pump offshore if you're interested 150£