Trim dropping down over time and under load

[Ian MacAulay]

Morning.

The trim on my alpha 1 leg drops very rapidly under load and also over a few hours on the trailer.

Now would this be the rams or the pump and if its the pump what should I check or replace
?

Thanks

Ian

 

[oGaryo]

I'm presuming there's no visible signs of leakage from the rams when on the trailer not milkshake in the trim reservoir. If so, operate the leg in the water and look for a film of oil on the surface to be sure as that will pick up the smallest of leaks. If none exists, then it is likely to be the valves in the pump not holding the pressure.

 

[Ian MacAulay]

Many thanks


There is no leaks and no drop in oil in the tank.

Is it possible to have the block repaired

Thanks

Ian

 

[oGaryo]

Sorry, when you say 'block' do you mean the valve body between the motor and the reservoir on the pump? Presume you have something that looks similar to this Ian

The first step I'd take if you have a mate with a similar boat is to swap his pump with yours (easy to do) and see if that resolves it.

 

[Ian MacAulay]

Yes I have that. Would the block between the motor and reservoir be my issue? I have to spare rams so is it worth changing them?

Thanks

Ian

 

[alt]

I had this on a boat I had years back. I was told it was the 'internal seals' on the rams leaking as there was no water ingress and oil was not leaking

 

[Ian MacAulay]

Thanks

So its likely that both rams would give up at the same time? Are they easy to change as I do have a spare pair

Ian

 

[oGaryo]

Yes I have that. Would the block between the motor and reservoir be my issue? I have to spare rams so is it worth changing them?

Thanks

Ian

it would be Ian as you're able to wind the drive up and down, I doubt it's the motor. a test you can do is to put the drive midway and then have someone stand on it to see if the pump is strong enough to move the drive with load on it. I had exactly this issue recently on my Volvo DP290 drive and it turned out to be an issue with the valve block for sure after a process of elimination. Changed it and all worked well.

I'd still go for the pump as main suspect, having both trim rams fail at the same time doesn't sound prime suspect to me i.e. if one has failed, I'd imagine the other would be able to keep the drive up when on the trailer.

I guess you can also check that it's not something really simple like the cap to the reservoir hasn't failed. presume you've also checked there's sufficient fluid in the rservoir

 

[Ian MacAulay]

It does raise while under load in the water going about 20knots but instantly drops down again

Thanks

Ian

 

[oGaryo]

It does raise while under load in the water going about 20knots but instantly drops down again

Thanks

Ian

that'll be the force of the prop pushing it down. having someone stand on the drive mimics that force so you can diagnose what's happening on dry land

 

[Ian MacAulay]

Hi.

I've changed the rams and its holding

 

[Ian MacAulay]

I have changed the rams and its holding but over a couple of weeks on the trailer is still dropping slowl . Is this normal? I've not water tested as of yet

Thanks ian

 

[dingdongs]

if on a trailer keep in the lower position to prevent bellows from setting and its not natural to leave up as could fill with water and freeze crack the lower leg.looks as though the rams were at fault.

 

[Ian MacAulay]

Morning thanks for the reply. I normally leave in the lower position but have kept it up since changing the rams to see if they are droppin .

They are still very slowly dropping over a week or two but is this normal or is something still letting by?

Thanks

Ian

 

[Beamishken]

It only needs the seal in one ram to be passing & the drive will drop as they are linked so if the fluid passes one it will allow the other to drop too
It sounds like your on the right track so maybe swap the rams one at a time as you might have 2 good ones out of the 4 alternatively the seal kits are quite cheap about £20 for copy ones & fairly easy to change

 

[Ian MacAulay]

Thanks.



I still got the issue so looking at changing the pump... But before i do this am i using the right oil in the pump... book says 10 40 SAE and i have Atf trans fluid in mine.. could this thinner atf fluid be a issue?


Thanks

Ian

 

[Beamishken]

atf is fine being red its easier to spot leaks too