1990 Mercury Black Max 175 HP (power trim) Problems

WHW819

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Jul 25, 2017
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Alright, ladies and gentlemen. Brand new to the forums here and I need some (a lot) of help. I bought an old Aquasport with a 175 Black Max on it recently. I was told the motor sat for approximately 6 years before I bought it. I figured this was a good chance to learn how to do fiberglass work and finally figure out how outboards work. Needless to say, I am a complete and utter novice at all of this. I've decided to start with the motor, since the fiberglass is a moot point if the boat don't run. So, to start, it obviously doesn't turn over. But, while I was screwing with it, I found that the power trim will go up, but not down. I have seen similar posts about this and most of them just say to clean everything and make sure the connections are good and clean, which I've done. I disassembled what I'm pretty sure is where the trim motor draws its power from, cleaned all of it, replaced some connectors and re-assembled it (SEE ATTACHED PHOTO FOR WHAT I DISASSEMBLED AND CLEANED) Same results. I found the nylon screw that you can use to bypass and lower the motor manually. That's all well and good, but I just can't seem to figure out why the "down" trim button will only provide an audible *click*, but not run the trim motor. The "up" button doesn't hesitate or stall; works as it should. This is just the beginning of what will be a long learning curve in getting the motor running, but i'm determined. Any help will be very much appreciated.
 

WHW819

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Every time I try to add an attachment I get a message saying "You Are Not Authorized To Create Or Remove Attachments"
 

Dukedog

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there should be large (#10/maybe 8 wire) green on tha large post on tha solenoid thats clickin'.. check it for 12v when down is pushed or disconnect it and apply 12v positive straight to it... if pump runs tha solenoid is bad...
 

sam am I

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Jun 26, 2013
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What Duke said or (less probable, but can occur) some where's along the larger green wires path to the trim motor, there's an open. Including but, not limited to, the connection of this green wire at or internal to the trim motor......As such, use a jumper wire of similar gauge or a screw driver to jump across the two large studs at the suspected bad down solenoid.

When jumped (It should arc a tab bit when jumper'd, that's normal).......

Motor/trim works = Bad solenoid. (Very likely the case here as Duke indicated)
Motor/trim doesn't works = Green wire open to or at/in trim motor.
 
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WHW819

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Okay, great. Thanks, Duke! Ran positive straight to the big green and the pump ran and the motor dropped. As you said, bad solenoid. Now, again, being a total noobie, how can I replace the solenoid? Will I still be able to find one suitable for a 1990 easily? Or is it gonna be a special order sort of deal
 

Dukedog

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part number 818864....... call around.. look on ebay.. should be plenty of 'em.. 30 some odd bucks or less.
 

WHW819

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Jul 25, 2017
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Excellent, guys. Thanks again. Picked one up just down the road, installed it and the trim works as it should, up and down... Now the next issue:

On the bottom of the mounting bracket, there are two (pins? rods? sticks?) that also appear to be hydraulic. When I trim the motor down as far as it will currently go, the motor hits these pins and stops. Seems to me it should push these in, or I should be able to manually change their location so the motor can trim all the way down to where it would be while I was running the boat. I attempted to upload a video for clarification, but it seems to have gotten quite blurry in the process. I will provide the link anyway.

As you can (hopefully) see briefly at the end of the video, the motor doesn't appear trimmed down nearly enough to run it and plane. How do I control these pins/rods/sticks?
 

sam am I

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