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2003 Mercruiser 4.3L Trim Pump Leak

bananaboat

New member
My trim pump sprang a leak this weekend while I was trimming the motor up. It's extremely difficult to access the pump but it appears to be leaking from the fitting on the left side of the pump body.

Can anyone provide me with direction on how to tackle this repair and what parts to order? I'm wondering if there might be an o-ring behind the fitting that blew out and if that might be the cause of the leak.

The boat is remote so I need to ensure I take all necessary parts. Thanks for any help you can offer, I really don't have a clue where to start.
 

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I should also mention that I don't know the serial number for my engine. It's not visible on the flame arrestor and I have limited access to the engine block and haven't been able to contort myself into position to see it.
 
Yes, there is an O-ring at the fitting but technically speaking, they don't seem to offer a size of O-ring or part number to buy one though a new O-ring does come with a new fitting when ordered.... so depending on the route you follow, you may need an assortment kit of O-rings if you don't buy a new fitting before heading out to the boat.

But to note, Merc used 2 different part numbers in which one came with a screen/filter while the other main one I believe more normally used didn't have the filter.
18808727CONNECTOR, (.437 UNF To .250 Inverted Flare) (No Filter Screen)ACT$18.90$18.432
18865590CONNECTOR, (.50 UNF To .25 Inverted Flare) (With Filter Screen)ACT$44.92$44.112

The following info can be used as a helpful guide,

That mentioned, just judging by the photo, it "appears" that maybe the fitting wasn't fully seated when installed as it looks like there are some fitting "threads" that you can still see (and maybe no O-ring too?) vs the other one on the right that is fully seated/tightened down.

Should use Mercruiser power trim and steering fluid,

Or similar, https://www.marineengine.com/boat-a...tm_term=marineengine&utm_content=All Webpages

Flare wrenches would be best suitable for this repair, https://www.harborfreight.com/hand-tools/tool-sets/wrench-sets/flare-nut.html,

Good luck.
 
Thank you very much for your help, I really appreciate it.

I think I'll buy a new fitting with the o-ring. Roughly how many containers of power trim fluid should I take?
 
Buy two qrts of power steering fluid at any auto parts store.

There is a fill line on the plastic resevoir and the level is check with outdrive all the way down.

Also the yellow plastic cap has a very small hole in it. That is a vent hole!!!
 
I should also mention that I don't know the serial number for my engine. It's not visible on the flame arrestor and I have limited access to the engine block and haven't been able to contort myself into position to see it.
Your title/registration should show the serial numbers.
 
Thanks everyone. I hope replacing the fitting is the fix but I don't want to waste a bunch of expensive Power Trim fluid if it's not. Power steering fluid or 10w30 would be more economical. Would one better than the other?
 
These OilDyne pumps can be rebuilt. There are also some things to do whilst the unit is out. The bottom plastic reservoir is held on by a single long machine screw. There's an o-ring on it to seal the thing from leaking. Also inside the reservoir is a pick up and return that has a filter screen on it. You might as well do a complete service on the thing and put new seals all around, new filter screens and flush the pump of old fluid. You can also get a new reservoir tank if yours is dirty or otherwise so you can't see the level. Use power steering fluid, not red ATF. Don't go cheap on boat repair.
 
I'm gathering my supplies for this repair and am going to tackle it next weekend. This may be a dumb question but, can I use synthetic power steering fluid?
 
I went over to West Marine and bought their brand, you can also use Sierra brand.
Just redid both of my 36 year old Cobra trim cylinders. One was leaking and the ram rods were both pitted and the aluminum eyelets on the ends were really corroded. So I left the original rams on the boat, removed the old pitted rods and replaced them with a good used set with all new seals. If you can get the end caps off it's not a hard job at all.
No boating supply stores where you are? No marinas?
It may not really matter, I know in my OMC shop manual it said to use their T&T fluid, or Dexron II
I used the T&T fluid because Dex II isn't that easy to find, and the later versions may be formulated a bit differently.
Just be careful with those hydraulic fittings, use a proper line wrench, like for brake lines.
 
There is no need to buy any special brand of "power trimp fluid"

It is power steering fluid plane and simple.

Every auto parts store sells it. Brand or non or syn does not matter.

Dont waist time thinking about it.

Yes GM type transmission fluid works also if you so desire.
 
I went over to West Marine and bought their brand, you can also use Sierra brand.
Just redid both of my 36 year old Cobra trim cylinders. One was leaking and the ram rods were both pitted and the aluminum eyelets on the ends were really corroded. So I left the original rams on the boat, removed the old pitted rods and replaced them with a good used set with all new seals. If you can get the end caps off it's not a hard job at all.
No boating supply stores where you are? No marinas?
It may not really matter, I know in my OMC shop manual it said to use their T&T fluid, or Dexron II
I used the T&T fluid because Dex II isn't that easy to find, and the later versions may be formulated a bit differently.
Just be careful with those hydraulic fittings, use a proper line wrench, like for brake lines.
Dex II was sped'd because that was the PS fluid used at that time- newer boats spec more recent versions of PS fluid. It's nothing special, it just needs to A) be in the reservoir and B it needs to be clean.
 
I personally have never seen a spec for trans fluid for merc trim pumps.
On the old versions pre 1980 maybe, they spec'd 20 weight oil and I believe that was due to the pump pressure and trim ram design.
I know that since '80s and especially with the current plastic resevoir design, Power Steering fluid is what is specified for use and can be substituted with GM type trans fluid. The Key word is substituted.
 
I personally have never seen a spec for trans fluid for merc trim pumps.
On the old versions pre 1980 maybe, they spec'd 20 weight oil and I believe that was due to the pump pressure and trim ram design.
I know that since '80s and especially with the current plastic resevoir design, Power Steering fluid is what is specified for use and can be substituted with GM type trans fluid. The Key word is substituted.
The plastic reservoir came in because the steel ones rusted, but neither is under pressure. Technically, any fluid could be used- it's just a small hydraulic system and these recirculate the fluid, so they don't need to be bled.

W20 has been used in marine transmissions, too- I worked on lots of older ski boats with Hurth and Borg Warner that had the oil type on a metal tag. In some cases, the manufacturer recommended changing to W20 but I'll need to look in my tech notes to find the reason.
 
Power steering fluid is around 10 W. As is many hydraulic oil for many applications.

I wonder why Merc sells "Power Trim" fluid by the bottle which is power steering fluid...
 
Power steering fluid is around 10 W. As is many hydraulic oil for many applications.

I wonder why Merc sells "Power Trim" fluid by the bottle which is power steering fluid...
A friend asked Ray Kimber (founder of VERY expensive Kimber Cables) why he charges so much and Kimber answered with "Because I make a lot of money".

Brunswick (Mercury/Mercruiser), OMC, Volvo-Penta and others sell accessories so the owners of their products have a variety of places where they can be purchased and sometimes, they recommend ONLY using their own products for lube, parts, etc and in some cases warranty depends on this.

OTOH, for some people, seeing 'Power Trim' on a bottle just makes it less likely that they'll put the wrong stuff in.
 
A friend asked Ray Kimber (founder of VERY expensive Kimber Cables) why he charges so much and Kimber answered with "Because I make a lot of money".

Brunswick (Mercury/Mercruiser), OMC, Volvo-Penta and others sell accessories so the owners of their products have a variety of places where they can be purchased and sometimes, they recommend ONLY using their own products for lube, parts, etc and in some cases warranty depends on this.

OTOH, for some people, seeing 'Power Trim' on a bottle just makes it less likely that they'll put the wrong stuff in.

When one works in the business you learn what OEM products should be used and which are the same as other products just in a OEM package
 
When one works in the business you learn what OEM products should be used and which are the same as other products just in a OEM package
I know- I worked for three boat dealers, but the fact is, many products can be used as substitutes with good/great results. Parts are often different- substituting can cause problems. One example is OEM raw water pump housings from Merc use a different plastic from what is used in Sierra, but the Sierra work fine unless the impeller ends up like the one in my boat (little, tiny pieces laying in the water pickup area below the pump).
 
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