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  1. #1
    Cadet
    Join Date
    Jul 2011
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    2

    Default mercruiser pre alpha trim pump settings?

    hi,
    i recently had to install new brushes in my trim pump motor and decided it would be a good idea to clean the pump valve body while i had the thing out of the boat. well, i unscrewed the 3 threaded set screws(the ones with the allen heads) without realizing that these must be for setting the flow of oil. i realized it when i put everything back together and my trim was acting weird--going up kinda slow, going down super slow, and also when it would get to the all the way up position, the pump would bog out and stop running-like it was straining to go up more;before it would just change pitch in sound when it was all the way up. anyway, does anyone know what the setting of these screws should be? like how many turns out from a seated position? im totally pulling my hair out with this problem! my dealer says the pump is a non servicable part, but i just cant beleive that.

  2. #2
    Honorary Moderator Emeritus Don S's Avatar
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    Aug 2004
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    Western WA.
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    Default Re: mercruiser pre alpha trim pump settings?

    The words "Pre Alpha" narrows it down to about 3 different trim pumps. Can you help us with engine model and serial number, drive model or SN, or even a year might help a little.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  3. #3
    Cadet
    Join Date
    Jul 2011
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    2

    Default Re: mercruiser pre alpha trim pump settings?

    ok sorry. its off a 1975 searay with a 165 I6. the pump is a prestolite, the motor is a cylinder shape and it sits on a square pump body/reservoir. i will have to go to where i keep my boat to get some #s off it if this info is still too vague.

  4. #4
    Fleet Admiral
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    Aug 2004
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    East coast NJ
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    Default Re: mercruiser pre alpha trim pump settings?

    Unless I missed it,manuals 2 and 4 make no mention of adjusting the valve body, just replacement.
    message me if interested about another one.
    NO PERSONAL QUESTIONS, THIS IS WHAT THE FORUM IS FOR.

  5. #5
    Cadet
    Join Date
    Feb 2010
    Location
    myrtle beach, sc
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    Default Re: mercruiser pre alpha trim pump settings?

    thanks Bt Doctur. iwent to message you but it says your inbox is full or something
    yeah i have a clymer, and it it shows some pics and explains a little what each valve does but nothing about adjustment. one of the local merc marine mechanics basically said they just replace them. i was gonna buy a new pump from sei for 300, but when i called them this morning he said all their pumps are low pressure/high volume pumps and mine is high pressure/low volume. i found a replacement for 550, and another for 730, but to be honest, im not 100% sure the problem is my pump or something else. i had trim cylinders rebuilt, so they should be good, there isnt really anything else that can be making this thing not work other than the pump right? i thought about by passing the reverse lock and trim indicater to eliminate those as problems, but is there really anything that can go wrong with those?, other than maybe a leak? man this is maybe the most frustrated ive ever been working on my boat.

  6. #6
    Vice Admiral
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    Jan 2008
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    Vegas
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    5,765

    Default Re: mercruiser pre alpha trim pump settings?

    I'd bypass the reverse lock valve and the trim indicator to see if the pump and cylinders work properly, then add in the reverse lock and trim indicator. The reverse lock valve is adjustable, and needs to be adjusted properly, but I'm not sure where instructions are, I've seen them, but don't remember which manual has them. Since you had the pump torn apart and the adjustment screws are out of whack, I think you know what the problem is..

    BTW, If BT doesn't have anything, I have one.

    Quote Originally Posted by jeff593 View Post
    i was gonna buy a new pump from sei for 300, but when i called them this morning he said all their pumps are low pressure/high volume pumps and mine is high pressure/low volume.
    I'm using a new style Oildyne pump with 73 Mercruiser (M1) 140 trim cylinders and trim indicator, it works just fine. The good thing about the new style pump, you can leave the reverse lock valve out of the hydraulic circuit, the pump handles the reverse lock. The reverse lock valve is still needed for the shift cable anchor points, so I just filled mine with oil and capped it off.

    Good luck,
    2001 Crestliner SuperHawk 1800, Mercruiser 140HP
    2007 Tracker 1436 jon boat, 7.5HP Force

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