TIlt/Trim Reverse Lockout 1971 165 I-6

system-f

Senior Chief Petty Officer
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Dec 3, 2008
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1971 165 Inline 6 tilt/trim problem. I have read everything I have searched which just generated more questions.

The problem: Drive will not go all the way down. Up is 100% ok, down only about half way then stops and tilt/trim pump sounds like it is loading down but still runs.

I suspect the reverse lockout, because taping it gently with a hammer allowed the drive to go down a little bit further before the pump started to sound bogged down.

Can I convert to a newer pump with the lockout built in and use the tilt/trim position ram on the transom? If so will my brand new stainless steel lines work, ie: except for bypassing the reverse lockout is it a bolt in as far as hydraulics are concerned? If all of this is true, which pump do I buy....iboats link ?

If I cannot convert is the reverse lockout rebuild-able?
 

system-f

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As an update, I went and bled the trim sending unit and the drive now returns to full down position. I would still like to know if an upgrade to the newer pump with the built in lockout is available.
 

system-f

Senior Chief Petty Officer
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Dec 3, 2008
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UGH, it looks like the bleed didn't fix the problem. This morning I lifted the drive all the way up and it went back down until it reached the top of the trim and then stopped as the motor sounded like it was loading up again. I would gladly plop down the cash for a new pump unit.
 

fishrdan

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Jan 25, 2008
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I did the same conversion on my 73 140 HP Mercruiser with reverse lock valve and hydraulic trim sender. That pump you linked to will work for the conversion (try Ebay) and you will need to re-route around the reverse lock valve, while keeping the trim sender in the loop. You need to keep the reverse lock valve as it's used to operate the shift cables, I filled it with oil and capped it off. I was doing a complete rebuild at the time and replaced all the hoses:

Pump -> Manifold
Manifold -> Trim sender
Trim sender -> Pump

It's been 6 years since my conversion, so I'm not 100% sure which hoses-fittings you will need, but I did use some brass adapters to make the hoses fit the pump. FWIW, I used stock Mercruiser tilt-trim hydraulic hoses. On an Alpha it takes 2 hoses, but I used 3 on my MC-1 to retrofit.

There is a difference in the old/new pumps as one is low pressure/high volume and the other is high pressure/low volume, I don't remember and assume the old style is low pressure due to the thin (nylon?) tubing used. This was one reason for changing out all the lines inside the boat, to handle the pressure of the newer pump. I have blown 2 trim ram lines since the conversion, but this could just be due to old age and kinking a line......
 

Grandad

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Jun 7, 2011
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I'm no trim expert, so I would start simple. Since you mention that the trim pump motor sounds like it is encountering an increased load at the point where movement stops, I would first suspect some form of mechanical issue at that point. If for example, the tilt swivel pins were badly worn or broken causing a misalignment, the drive would no longer settle easily into place. Removing the one rod that connects the outboard ends of the piston rods from the outdrive would allow you to manually raise and lower the drive to see if there is any unusual slop or side motion. Then, with the cylinders still disconnected, you could see if the pistons will power past this point in their travel that usually stops the motion. Be careful though, without a mechanical limit, perhaps the cylinders could be damaged by over-extending their travel. - Grandad
 
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