AAAGH Power trim again, 2nd installment

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whisper

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Following the major problems with our DP-E trim, reported on earlier, we bought a new pump and had it fitted. This follows repairs to the trim pistons which was intended to resolve the situation.

B****r me if on the 2nd test run we had the same problem reappear.
Symptoms are :-
1) When stationary, trim works as it should.
2) Under low load in forward gear the trim raises up when required but drops back down rapidly on its own. eg will if required raise up to +5. Then over about 10 secs drop back to -3
If one then knocks it out of gear the trim rises off its own bat from -3 to +4. It's as if it is acting like a spring.
3) When more power is applied in forward gear the trim won't lift up at all.
4) When put into reverse the trim rises continually, of its own accord. Then, when knocked out of reverse, it falls back down again.

This problem has only appeared since the existing rams were repaired.

Any more suggestions re. a cure would be greatfully accepted before we have to fork out yet another large sum for a new pair of rams.

Anyone know where the cheapest rams could scourced - I'd normally go via Keypart?

Thanks
 
Is the leg actually moving or is it just the helm indicator saying its moving.

I am now on my third trim "sensor" which are notorious for failure.
This one has been fitted to fool the EVC, does give silly readings but the trim works perfectly ok.
Doug
 
Thanks Doug,
We are going to check on this in about an hour's time, when we've got enough water.

Begining to doubt the wisdom of having an outdrive, especially with us being on a drying berth.
If it wasn't a Targa we may have already sold her. Absolutely love the boat but growing to hate the mechanicals.

Test now done and leg is doing what it says it is!
 
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I would remove the rams and get them checked by a hydraulic specialist to try and eliminate them as the problem first. If it's not the rams it has to be the pump, I know you've replaced it with a new one but the new one could be faulty. Is there anyone you know that has a similar setup that you could swap the pump out of to eliminate this?
 
Thanks for your suggestion Nigel,

When you say rams do you mean the pistons or the whole piston & cylinder combo?

Pistons have been removed, welded and polished, fitted with new seals and re-fitted.

Some debris (seal breaking up) was found in one of the cylinders and this was cleaned out - prior to re-fitting.
 
Personally I would remove both rams complete, it's a pain to do the first time you do it but it should allow for them both to be tested fully (took me quite a while first time i did it mainly figuring out how the make up a puller for the ram pin that fitted between transom and shield). I assume this is a single engine setup so are you reliant on this for your boat trim or could you work with it and trim tabs until the end of the season? (assuming your reverse catch prevents the leg rising too much)
 
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Hello again,

We've actually decided to do as you suggest and live with it until the boat comes out of the water in the Autumn.
Just have to avoid emergency reversing - might be difficult when trying to avoid the Salcombe Sailing Melee. Also mustn't forget to tie the leg up every night

I wasn't aware that there was a safety mechanism to prevent the prop rising uncontrollably in reverse.
 
Probably as you say the best thing to do is enjoy you boat this summer and sort it out over the winter.
My drives are 290dpa's - they have a reverse latch to prevent rise up in a ram failure or impact situation. I now realise that dpe's may not have this. Apologies for this.

Nigel
 
Can someone explain why we have the "spring" effect?

In neutral we set the leg at +6.
Go into slow ahead and leg slowly drops - increasingly rapidly as more power is applied - ends up at -2 or-3.
Back into neutral and leg rises back up to approx. +4 , of its own accord.

Sounds to us like an obvious case of air in the system. What else could it be?
 
Sounds more like the thrust from the prop is pushing the leg towards the transom with power on and the when the power comes off the drag effect of the leg in the water is pulling it back out. All sterngear has massive drag. Try pulling a dinghy with it's painter by hand with the outboard up and then try pulling it by hand with outboard down and you'll see what I mean- the difference is not subtle.
 
I do not know this particular system, that said, all hydraulics have a pressure relief valve, have you checked the pressure relief valve, it is there to protect the system, however, if it is set to low or if it is faulty it prevents the system from working correctly. Check that the contamination has not impacted the valve.
 
the rams are also fed from either side to raise or lower the leg, if the seals are faulty they will allow oil to "pass" from the pressure side. have you considered having the rams re-sealed, if the piston rods and cylinders are OK and true then a reseal should be a lower cost than replacing the ram
 
Nigelhg said:
Sounds more like the thrust from the prop is pushing the leg towards the transom with power on and the when the power comes off the drag effect of the leg in the water is pulling it back out. All sterngear has massive drag. Try pulling a dinghy with it's painter by hand with the outboard up and then try pulling it by hand with outboard down and you'll see what I mean- the difference is not subtle.
Click to expand...

Thanks for the reply. We don't think this is a "drag" thing because some of our tests have been done with boat tied up alongside. When we go ahead, all the lines tighten up and the boat strains to go forwards. The leg steadily drops down to -3.
Put gear into neutral and the boat springs backwards and the trim rises. The drag of the leg would tend to make the trim go further down (or stay at -3) rather than go back up. It really is reacting as if the rams are spring loaded.
 
Tidnock said:
the rams are also fed from either side to raise or lower the leg, if the seals are faulty they will allow oil to "pass" from the pressure side. have you considered having the rams re-sealed, if the piston rods and cylinders are OK and true then a reseal should be a lower cost than replacing the ram
Click to expand...

Thanks,
The rams were re-sealed when they were refitted, after repair to the "pistons". No noticeable difference was the result.
 
whisper said:
Thanks,
The rams were re-sealed when they were refitted, after repair to the "pistons". No noticeable difference was the result.
Click to expand...

Sometimes you can keep trying things, perhaps fitting costly parts and making unnecessary adjustments that can cause other problems elsewhere. I have not read you first post so excuse me if I have missed something, however, have you thought of letting the dealer look at it, he may go straight to the problem.
 
I think he only had the rams checked but not the cylinders so what you said about the oil going from one side to the other sounds about right.
 
Tidnock said:
Sometimes you can keep trying things, perhaps fitting costly parts and making unnecessary adjustments that can cause other problems elsewhere. I have not read you first post so excuse me if I have missed something, however, have you thought of letting the dealer look at it, he may go straight to the problem.
Click to expand...

Hi,
Dealer has re-fitted rams (pistons). Problem becomes apparent - after tests dealer suggests new pump.
We fitted new pump - problem still apparent.
Dealer had boat lifted and checked system out - found "debris" in one cylinder - cleaned/refitted - problem still apparent.
Dealer at a loss to know what the cause is - neither he nor we understand what can be causing the "spring back" effect described earlier. Suggested we remove and replace both rams/cylinders.
I just worry that having forked out another £2k to do this job, it won't provide a cure, in the way that all previous attempts have panned out.
 
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