No Power Steering- 1998 Mercruiser 7.4 MPI

Y

yeesh

New Member
Jan 11, 2012
11
Broad Channel,NY
Boat Info
1999 Searay Sundancer 270
Engines
454 Mercruiser w/ Bravo III Drive
1998 Searay Sundancer 270 (7.4 Bravo MPI) laid up for several years. Gradually got all systems go, but have no power steering. Not having a gauge set, and assuming dried out seals in the empty pump might be the problem, I cracked open the high pressure out fitting on the back of the pump with engine running and fluid just drained out. I figured it would spray out, so installed a new pump. I filled it with fluid and with the engine running and pump fill cap off, I turned the steering wheel fully each way probably 40 times. No change. (Also determined that loosening the fitting on the new pump had same result- no apparent high pressure). Prior to this, I took the clevis pins out of both the steering cable and the gimbal steering arm. Both cable and arm move freely on their own. I hate to change the actuator and still end up with a problem. Are their any tests I can do to find and resolve the problem? Getting so close! Appreciate any advise on this. 1998 7.4 Bravo MPI. (4542067M1). Thanks
 
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I believe that the engine should not be running when you are bleeding the steering. Start with the drive straight back and fill to cold. Next WITHOUT the engine running steer from lock to lock several times. See if this will bleed the system. Add fluid as necessary. Then start the engine and repeat the steering lock to lock several times with the cap replaced on the pump. If the fluid foams in the pump you are making progress. Add fluid to the hot line and repeat until the fluid stops foaming.

I have only done this one time and I am no mechanic but this is how I did it on a 3.0 mercruiser.
 
@blaster The engine does need to be running to bleed it correctly. Its basically a mid 90's General Motors style power steering pump that runs to the actuator and then back via a return line so it's constantly circulating. The actuator gets pulled left or right according to the input from the steering cable as you turn the wheel. It then applies a hydraulic assist to the cable steering to move the outdrive left or right. If the pump was dry long enough it has likely failed. Odds are it lost all its fluid due to a broken line somewhere in the bilge. @yeesh Change the lines as needed and swap out the pump first. If its still nonfunctional then change the actuator.
 
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yeesh said:
1998 Searay Sundancer 270 (7.4 Bravo MPI) laid up for several years. Gradually got all systems go, but have no power steering. Not having a gauge set, and assuming dried out seals in the empty pump might be the problem, I cracked open the high pressure out fitting on the back of the pump with engine running and fluid just drained out. I figured it would spray out, so installed a new pump. I filled it with fluid and with the engine running and pump fill cap off, I turned the steering wheel fully each way probably 40 times. No change. (Also determined that loosening the fitting on the new pump had same result- no apparent high pressure). Prior to this, I took the clevis pins out of both the steering cable and the gimbal steering arm. Both cable and arm move freely on their own. I hate to change the actuator and still end up with a problem. Are their any tests I can do to find and resolve the problem? Getting so close! Appreciate any advise on this. 1998 7.4 Bravo MPI. (4542067M1). Thanks
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I have the manuals for the '98 7.4 and the Bravo 1 drive, if you need them. Gives all the info needed on repairing and maintenance of the power steering system.

PS: FYI - Never had a bravo that was super easy to turn, like car steering. Maybe they should be, but have never driven one like that. Had one that had PS line rupture and it was nearly impossible to steer underway.
 
Thanks for the reply. I do have a Seloc manual that’s hit or miss. The boat is out of the water- maybe it’s just a super assist system like you said. I’ll probably launch it and see how it goes.
 
Hoplite808 said:
@blaster The engine does need to be running to bleed it correctly. Its basically a mid 90's General Motors style power steering pump that runs to the actuator and then back via a return line so it's constantly circulating. The actuator gets pulled left or right according to the input from the steering cable as you turn the wheel. It then applies a hydraulic assist to the cable steering to move the outdrive left or right. If the pump was dry long enough it has likely failed. Odds are it lost all its fluid due to a broken line somewhere in the bilge. @yeesh Change the lines as needed and swap out the pump first. If its still nonfunctional then change the actuator.
Click to expand...
 
Thanks. I did replace the pump with a new OEM one, so that should not be the problem. The high pressure hydraulic line from the pump to the actuator is intact- no leaks; ditto for the low pressure return line. Fluid level stays at full in the pump, and no leaks. So I’m guessing it’s the actuator, or a blockage. Do you know offhand if the pump creates enough pressure to where it would spray out when loosening the high pressure hydraulic line in the back? Tried this with both thevold and new pump and fluid just drains straight down. Thought there’d be pressure with the engine running and pump spinning. Tnx
 
It’s not so much high volume of fluid but rather high working pressure of the fluid since it’s a hydraulic fluid. A gauge on it would be the only way to measure correctly but that would be prohibitively expensive for what it is. If you are sure there are no leaks and it’s a new pump and it’s not making noises then it’s likely the actuator failed. You’ll have to disconnect it from the back of the motor and pull it out to work on it.
 
You need the mercruiser manuals? If yes, send me a PM and I'll upload and give you a link to my GoogleDrive folder
 
blaster said:
I believe that the engine should not be running when you are bleeding the steering. Start with the drive straight back and fill to cold. Next WITHOUT the engine running steer from lock to lock several times. See if this will bleed the system. Add fluid as necessary. Then start the engine and repeat the steering lock to lock several times with the cap replaced on the pump. If the fluid foams in the pump you are making progress. Add fluid to the hot line and repeat until the fluid stops foaming.

I have only done this one time and I am no mechanic but this is how I did it on a 3.0 mercruiser.
Click to expand...
Great! Thanks for that advise. I had been trying to bled it while running. I’ll try it with the engine off now.
 
Bill Curtis said:
You need the mercruiser manuals? If yes, send me a PM and I'll upload and give you a link to my GoogleDrive folder
Click to expand...
That would be great. New to this site, so I’ll just have to figure out how to pm you. Thanks!
 
yeesh said:
That would be great. New to this site, so I’ll just have to figure out how to pm you. Thanks!
Click to expand...
blaster said:
I believe that the engine should not be running when you are bleeding the steering. Start with the drive straight back and fill to cold. Next WITHOUT the engine running steer from lock to lock several times. See if this will bleed the system. Add fluid as necessary. Then start the engine and repeat the steering lock to lock several times with the cap replaced on the pump. If the fluid foams in the pump you are making progress. Add fluid to the hot line and repeat until the fluid stops foaming.

I have only done this one time and I am no mechanic but this is how I did it on a 3.0 mercruiser.
Click to expand...
I think you’re right about the bleeding process. Someone else posted a procedure right from the manual that says the same. Thanks for the heads up- I’ll give it a try
 
Hoplite808 said:
It’s not so much high volume of fluid but rather high working pressure of the fluid since it’s a hydraulic fluid. A gauge on it would be the only way to measure correctly but that would be prohibitively expensive for what it is. If you are sure there are no leaks and it’s a new pump and it’s not making noises then it’s likely the actuator failed. You’ll have to disconnect it from the back of the motor and pull it out to work on it.
Click to expand...
I’ll pull it out and see if it’s even a rebuildable item. Probably end up buying a new one. Not cheap, but if it solves the problem I’m good. Before that, I’m thinking I’ll check where the fluid goes through the cooler and see if any obstructions. Thanks for the advice.
 
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