Repair of 1996 OMC 48 SPL Engine

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
Oldslowandugly
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Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Tue Apr 05, 2022 7:27 pm

In another thread I described how I rebuilt the lower unit from a 1996 OMC 48 SPL engine. I am now trying to get that same 48 SPL engine working as a spare engine.

The power trim and tilt was not working. When removing the trim and tilt assembly from the engine swivel bracket I saw that someone had tried unsuccessfully to drill out the upper pivot pin. They also managed to break off a part of the bracket opposite the pivot pin. I soon realized that the pin was corroded solidly to the swivel bracket and was not budging. That explained the damage from someone trying to get it out.

The lower tilt shaft came off easily. The upper pin had to be cut off with a cut-off disc on an angle grinder.

IMG_0386.JPG
Damaged swivel bracket. Note last bit of pivot pin remains.
IMG_0386.JPG (122.7 KiB) Viewed 1685 times


With the trim and tilt assembly free, I investigated why the power trim and tilt assembly did not work.

First step in any analysis of a hydraulically operated device: check the hydraulic fluid level. I opened the filler hole and foamy fluid spat out. That indicated air was mixed with the hydraulic fluid. The fluid reservoir was drained. New Dexron hydraulic fluid was added to the reservoir.

The hydraulic pump motor was tested by connecting it to a battery. A loud screeching noise was made, but the ram did move a bit. Repeatedly applying battery power to the pump motor in short bursts eventually resulted in the ram moving up and down--in fits.

After letting the unit rest and the letting the air expel from the oil, more hydraulic fluid was added to the reservoir to reach the fill line. With each addition of more hydraulic fluid, the unit worked better.

Eventually I was able to operate the ram through five full-up to full-down cycles, as the factory service manual recommended.

Next, with the ram in the up position, the level of the hydraulic fluid is checked. More fluid was needed to bring the reservoir to the full mark. Then the trim and tilt assembly began to work very well.

The pump motor looks new; I think someone replaced it, but did not follow the instructions to correctly fill the reservoir with hydraulic fluid.

IMG_0387.JPG
Trim and Tilt unit. Topmost screw beneath motor is to check the oil level.
IMG_0387.JPG (132.06 KiB) Viewed 1685 times
Last edited by Oldslowandugly on Tue Apr 05, 2022 7:55 pm, edited 1 time in total.

Oldslowandugly
Posts: 717
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Tue Apr 05, 2022 7:41 pm

The damaged swivel bracket was beyond repair; I searched on-line for a replacement. Green Bay Propeller and Marine in Wisconsin sold me a nice used swivel bracket from a 1992 40-HP engine--it was even the same color as I had.

The factory service manual recommends that removing the bracket requires removing the powerhead. I wanted to avoid that if possible.

For safety sake I bolted a 1-foot-long 2 x 3 to the thermostat housing. Even though I had the outboard engine suspended from a hoist, I needed to keep it from tilting sideways while working.

IMG_0385.JPG
Wood 2x3 bolted to motor for stability.
IMG_0385.JPG (161.68 KiB) Viewed 1680 times


First, I removed the mounting bracket from the engine.

Then I removed the lower exhaust housing clamps to free the swivel bracket. The steering arm is mounted in rubber biscuits and has some give. I started to bend the bracket and the steering arm away from the exhaust housing. I slowly bent it away, more and more, while jamming a piece of wood between the housing and the bracket. Care must be used to not to let the steering arm hit the lower carburetor. The arm will bend to the side a bit and clear the carburetor.

Once the bottom of the steering tube is clear of the exhaust housing, the swivel bracket can be tapped down and off the steering arm.

Clean the steering arm and all the parts before installing the new swivel bracket.

IMG_0382.JPG
Swivel bracket removed from steering arm with powerhead still in place.
IMG_0382.JPG (168.28 KiB) Viewed 1683 times

dtmackey
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Re: OEM Quality

Postby dtmackey » Tue Apr 05, 2022 10:32 pm

ASIDE: It'd be nice if outboard manufacturers weren't so cheap, and they would have spent a couple extra bucks for quality metal pieces that lasted. The cost impact to the engine's price would be minimal.

Oldslowandugly
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Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: OEM Quality

Postby Oldslowandugly » Wed Apr 06, 2022 12:05 pm

dtmackey wrote:ASIDE: It'd be nice if outboard manufacturers weren't so cheap, and they would have spent a couple extra bucks for quality metal pieces that lasted. The cost impact to the engine's price would be minimal.

This series of motors has the most stainless steel fasteners that I have ever come across. Remember the 1950's motors? NOTHING came apart easily. As a general rule, if not already stainless, I replace it with the best stainless available. Even hardware store 18/8 is better than cheap mild steel.
Last edited by Oldslowandugly on Wed Apr 06, 2022 12:43 pm, edited 1 time in total.

Oldslowandugly
Posts: 717
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Wed Apr 06, 2022 12:42 pm

After cleaning the parts swivel bracket I attempted to install it on the steering tube. I again pried the steering tube away from the exhaust housing until the swivel bracket could be loaded onto the steering tube. Here I found a problem. The manual states to load all the shims, seals, and bushings onto the bracket before sliding the steering tube into it. That may work with the powerhead off but not this way. The problem is that at the very bottom of the steering tube the diameter is slightly larger than the upper portion. That makes it a very close fit for the parts and impossible to get the bracket on with them in place. I loaded the shims and seals that belong at the top of the bracket first. Then I slipped the bracket onto the steering tube. There is a lip inside the bracket that wants to catch and stop the tube. By inserting a long pry bar inside the hollow tube I pulled the tube away from the bracket and then it went past the lip. At the very bottom of the bracket is a plastic washer. It went onto the bracket easily but was a very tight fit on the tube. I slowly tapped it up the tube with a 1.5" spanner and a hammer but then it stopped. I don't know why because it was from this same motor. I ended up breaking the washer and using the washer from the damaged bracket. That one went on easily. Once the swivel bracket was in place I could then replace the exhaust housing side clamps to retain the bracket. Here is the replaced bracket ready for the mounting bracket to be re-installed.
IMG_0388.JPG
Replaced swivel bracket.
IMG_0388.JPG (74.31 KiB) Viewed 1632 times

Oldslowandugly
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Location: Queens NY

Re: Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Sun Apr 10, 2022 4:38 pm

Today I mounted the motor mount bracket to the swivel bracket. Forget the big hammer. Use a length of threaded rod, nuts, big washers, and some short spacer pipes so you can press the tilt tube into the brackets smoothly and carefully. Clean and lube the plastic washers and tilt tube with Triple Guard Grease. Insert washers into the depressions on the ends of swivel bracket. Line up the mount bracket to the swivel bracket and insert the threaded rod with the tilt tube slid over it.
IMG_0390.JPG
Threaded rod about to press tilt tube in.
IMG_0390.JPG (74.36 KiB) Viewed 1604 times
Press the tilt tube in slowly and stop if it gets hung up. It should go in cleanly so don't force it. Initially the threaded rod will pull most of the tilt tube into the brackets.
IMG_0391.JPG
Tilt tube half way in.
IMG_0391.JPG (83.7 KiB) Viewed 1604 times
At some point you will run out of play and need to use a section of pipe larger than the tilt tube for it to slide into.
IMG_0393.JPG
Pipe sleeve lets the tilt tube be pressed inside.
IMG_0393.JPG (60.03 KiB) Viewed 1604 times
Continue drawing the tilt tube into the brackets until it is positioned correctly. You need enough threads to screw the tilt tube keeper nuts on but more on the starboard side for the steering cable nut to fit all the way. Torque the tilt tube nuts to 40-45 ft lbs then back off 1/4 turn. I felt that was too loose and sloppy so I hand tightened the nuts so there was just a bit of drag on the tilt tube.

Oldslowandugly
Posts: 717
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Sun Apr 10, 2022 4:42 pm

When the tilt tube is installed correctly there are enough threads on the starboard side to screw the steering cable nut on. If your steering cable is on the port side then leave enough threads on that side. The instructions on the steering cable nut say to screw it on completely and make it tight. If done correctly the steering cable nut will be on all the way and there will be a few threads left between the steering cable nut and the tilt tube nut.
IMG_0394.JPG
Note the longer threads on the starboard side of the tilt tube.
IMG_0394.JPG (86.13 KiB) Viewed 1604 times

Oldslowandugly
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Location: Queens NY

Re: Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Mon Apr 11, 2022 9:33 pm

UPDATE on the [repair of the trim unit]:

I temporarily installed the trim unit on the outboard engine. I was lifting and lowering the motor to check the operation with all that weight on it. I heard some squealing sounds and re-checked the oil level. The oil level was OK but I still suspected there was air mixed in.

Then I made the mistake of adding too much oil to compensate

The noise made while operating the trim unit sounded better, but the next time it cycled down oil squirted out from under the motor housing. This told me to NEVER over-fill the reservoir. It also told me that the seal under the motor was no good.

I removed the motor and found that whoever installed it used too little Adhesive M on the very thin O-ring that seals the motor to the pump. Some sections had none at all. I cleaned all of the adhesive off and re-sealed with the Ultra Black. After it cures for a day I will re-fill and test again.

UPDATE: the trim unit works better now. Perhaps the poor seal of the motor was letting air into the system.

Oldslowandugly
Posts: 717
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Tue Apr 19, 2022 5:20 pm

Another problem. When I raise the motor to the full up position, it slowly lowers back down. I have to check the pump emergency down relief screw to make sure it is tightened to the correct torque.

jimh
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Re: Repair of 1996 OMC 48 SPL Engine

Postby jimh » Tue Apr 19, 2022 5:23 pm

Examine the check valves in the hydraulic system. The check valves are what prevents flow of hydraulic fluid when the pump is not running. Perhaps there is debris in the hydraulic system and a check valve is not closing properly.

Oldslowandugly
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Location: Queens NY

Re: Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Tue Apr 19, 2022 5:47 pm

Yes, I was afraid of that. The FSM says to double check the emergency relief down first. If someone messed with it, it could be the problem. Otherwise it will require removing the motor and cleaning everything. At that point I may as well get an O-ring kit and just rebuild it. We shall see.

Oldslowandugly
Posts: 717
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Sat Apr 23, 2022 4:31 pm

The first thing I did was to remove the manual release valve. That had an obviously bad O-ring on the section that separated two orifices on the release valve. All I had on hand in that size was an HNBR air conditioning O-ring so I used it. I also removed the UP check valve and it looked clean so I just replaced it. It worked. Now the motor stays in the UP position without leaking down. BUT- now the pump makes a squawking sound when it is pumping in the DOWN position. Going UP is smooth and quiet. Anyone know what that may be about? I think that a rebuild is in order but I am busy getting the Whaler ready to launch. It will be a while before I can get back to the pump.

Oldslowandugly
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Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Fri May 06, 2022 8:40 pm

The rain chased me back down to the basement today so I looked at the T-n-T pump. I drained the oil and tested the motor. There was no noise so I knew the problem must be inside the hydraulic system. The only thing I changed the last time I worked on it was the O-ring on the manual release valve. I removed that again and what I found was a tiny sliver of the old O-ring had slipped down inside and was at the bottom of the manual release valve chamber. The valve must have been leaking under pressure and causing the squawking sound. I cleaned that out and replaced the manual release valve then refilled with oil. Now it woks just as it should with no noise. That just reinforces how important cleanliness is with this type of component.

Oldslowandugly
Posts: 717
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Sun May 08, 2022 10:10 pm

Today I finished fabricating a ground cable for the T-n-T. Since the mounts are insulated by plastic bushings you need a dedicated ground from the T-n-T to the outboard motor body. I used some 10 gauge marine grade wire and stainless steel ring terminals. I soldered and sealed them. Then I connected the wiring for the T-n-T to the motor harness to see if the cowling mounted switch worked. I hooked up a battery to the motor with jumper cables. When I pressed the tilt switch buttons I heard a sizzling sound from the relays. The tilt only worked in fits. When I removed the relays I saw that one had been epoxy-ed together. The other was covered in dark greasy stuff. I removed them and cleaned up the terminals and then they worked a little better. But I am ordering new relays any way.

Oldslowandugly
Posts: 717
Joined: Fri Jan 15, 2016 11:19 pm
Location: Queens NY

Re: Repair of 1996 OMC 48 SPL Engine

Postby Oldslowandugly » Mon May 09, 2022 2:19 pm

Today I tested the two T-n-T relays and a spare I had. All worked fine. OMC used a common relay used in many automobiles that is easily substituted for the expensive and hard to find OMC item. I unscrewed the relay mount from the electrical board. The back side was covered in dirty grease. I sprayed that with electrical contact cleaner and a small paint brush to get it off. While doing that I noticed that the three yellow wires coming from the alternator to the electrical board had all lost their insulation. More work before I am able to try and start this motor. I moved my wiring problems to another post here: https://continuouswave.com/forum/viewtopic.php?f=9&p=41586#p41586