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Author Topic:   Merc EFI 150 - Trim not holding motor up

tully_mars posted 07-21-2003 08:21 PM ET (US)
So this is a 98 Merc 150, one of the motors on my Conquest which is falling down a few inches every 24hrs when trimmed all the way up. Just wanted to get a quick survey of what the problem might be before I get into it, bad seals or just low on fluid?
Thanks
Tully Mars
acseatsri posted 07-21-2003 08:27 PM ET (US)
If it was low on fluid, it must have leaked out thru the seals. :)
lhg posted 07-21-2003 10:06 PM ET (US)
It's a hydraulic (seals) problem. Cost to fix a Mercury power trim unit can be considerable. A replacement unit is about $750 installed.
clanton posted 07-22-2003 09:36 AM ET (US)
The best guess without pressure testing is the pilot check valve seals inside the pump body. The seals are about 4.00 each takes 2. The parts not serviced by Merc. You can us a seal from a Force carbuator, or standard o-ring. You may find pn of seal and photos of a check valve at www.screamandfly.com, and at www.iboats.com, serch for 125 Force T/T for pn of seal. Precision in Clearwater Florida, may have the outside o-rings that seal pump body to T/T housing.
JohnNorthEast posted 07-22-2003 10:05 AM ET (US)
Same problem developed with my 1985Merc 150. The trim works fine otherwise but a seal leak causes very slow gravity drift over 24 48-hour periods. My mechanic strongly recommend against any additives and suggested just place a piece of wood under so that it sits on that at a mooring. Alternative was very expensive due to difficult accessing the area in need of repair.
Initially, I placed a wooden scrub brush handle, which worked fine, but decided I wanted a “fancier” fix and cut a piece of hard wood to fit. When not in use it rests in the stern unnoticed. Also place a large block of wood when in tow, as I want it at a different angle. That block rests comfortable in my truck when not in use.
hauptjm posted 07-22-2003 10:54 AM ET (US)
I had the exact same symptom with my 150hp OMC. I'm sure Mercury systems are virtually the same. My check valve at the top of the system has a little gasket that allowed just enough air to enter the system. Mine was under warranty so to be sure I sent it to the dealer to be "bench tested." Cost to OMC was $400+ to test. The fix was the $2.00 seal at the check valve.
Outrage18 posted 07-22-2003 03:08 PM ET (US)
I have had the same problem with my 1995 150 Mercury for the past 3 years...not big deal.
There should be a mechanical lever that will lock the engine in the "up" position.
Good luck!
-Paul
Bigshot posted 07-22-2003 03:32 PM ET (US)
Try the fluid first....if not then check valve. Mine got so that it would not hold the engine under power on my Yamaha so basically I only had power tilt or temporary trim.

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Author	Topic: Merc EFI 150 - Trim not holding motor up
tully_mars	posted 07-21-2003 08:21 PM ET (US) So this is a 98 Merc 150, one of the motors on my Conquest which is falling down a few inches every 24hrs when trimmed all the way up. Just wanted to get a quick survey of what the problem might be before I get into it, bad seals or just low on fluid? Thanks Tully Mars
acseatsri	posted 07-21-2003 08:27 PM ET (US) If it was low on fluid, it must have leaked out thru the seals. :)
lhg	posted 07-21-2003 10:06 PM ET (US) It's a hydraulic (seals) problem. Cost to fix a Mercury power trim unit can be considerable. A replacement unit is about $750 installed.
clanton	posted 07-22-2003 09:36 AM ET (US) The best guess without pressure testing is the pilot check valve seals inside the pump body. The seals are about 4.00 each takes 2. The parts not serviced by Merc. You can us a seal from a Force carbuator, or standard o-ring. You may find pn of seal and photos of a check valve at www.screamandfly.com, and at www.iboats.com, serch for 125 Force T/T for pn of seal. Precision in Clearwater Florida, may have the outside o-rings that seal pump body to T/T housing.
JohnNorthEast	posted 07-22-2003 10:05 AM ET (US) Same problem developed with my 1985Merc 150. The trim works fine otherwise but a seal leak causes very slow gravity drift over 24 48-hour periods. My mechanic strongly recommend against any additives and suggested just place a piece of wood under so that it sits on that at a mooring. Alternative was very expensive due to difficult accessing the area in need of repair. Initially, I placed a wooden scrub brush handle, which worked fine, but decided I wanted a “fancier” fix and cut a piece of hard wood to fit. When not in use it rests in the stern unnoticed. Also place a large block of wood when in tow, as I want it at a different angle. That block rests comfortable in my truck when not in use.
hauptjm	posted 07-22-2003 10:54 AM ET (US) I had the exact same symptom with my 150hp OMC. I'm sure Mercury systems are virtually the same. My check valve at the top of the system has a little gasket that allowed just enough air to enter the system. Mine was under warranty so to be sure I sent it to the dealer to be "bench tested." Cost to OMC was $400+ to test. The fix was the $2.00 seal at the check valve.
Outrage18	posted 07-22-2003 03:08 PM ET (US) I have had the same problem with my 1995 150 Mercury for the past 3 years...not big deal. There should be a mechanical lever that will lock the engine in the "up" position. Good luck! -Paul
Bigshot	posted 07-22-2003 03:32 PM ET (US) Try the fluid first....if not then check valve. Mine got so that it would not hold the engine under power on my Yamaha so basically I only had power tilt or temporary trim.