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engine stalls when steering wheel is fully turned to either side

toofast4uu

New member
Here's a new problem that i'm having a hard time figuring out.

1999 merc 4.3L TBI (EFI)

Engine runs fantastic and recently had full tune up and fuel pumps, etc...

when docking and turning fully to the left (or now to the right too) the engine will stall. If i'm quick and let off steering, it will stumble and regain rpms.

initially thought it was the IAC and replaced it, whereas it was intermittently improved, but issue came back and now it happen in both directions.


no noises and pump has fluid and it steers well outside of this issue.

any thoughts? my mechanic hasn't a clue as he hasn't experienced this before and thought it was the IAC. Hoping someone with more experience can share their thoughts.

thanks in advance,
 
What makes you think the drive is the issue? If the gimble or something else were not functioning correctly i would get a bad vibration or something. It a twin boat, and outside of this issue at docking speed it runs smooth and perfect.

just curious to learn more about what your suggesting. Thanks again
 
Here's a new problem that i'm having a hard time figuring out.

1999 merc 4.3L TBI (EFI)

Engine runs fantastic and recently had full tune up and fuel pumps, etc...

when docking and turning fully to the left (or now to the right too) the engine will stall. If i'm quick and let off steering, it will stumble and regain rpms.

initially thought it was the IAC and replaced it, whereas it was intermittently improved, but issue came back and now it happen in both directions.


no noises and pump has fluid and it steers well outside of this issue.

any thoughts? my mechanic hasn't a clue as he hasn't experienced this before and thought it was the IAC. Hoping someone with more experience can share their thoughts.

thanks in advance,





remove the p/s belt if it is a v belt and see if the problem is still there, wich it absolutely shouldnt be. then see how the steering is when the belt is off. you may have a bound up swivel shaft or frozen steering actuator, the pump is trying to compensate for.
 
As you know, the steering cable operates the slave valve, which in turn allows hydraulic pressure to operate the cylinder in either direction.
When the hydraulic cylinder reaches it's end of travel (either to port or to stbd), the slave valve doesn't know it.
During this, the pump is momentarily undergoing more pressure resistance.
This increase in pressure creates the need for more rotating force against the power assist pump.
It is possible that the increase drag on the drive belt is lowering engine RPM during the lock-to-lock position, therefor causing the engine to fall below idle RPM and eventually stalling.
You may want to check your idle RPM.

Most of these power assist pumps are nothing more than GM Saginaw pumps.
The pump's output pressure is controlled by a bi-pass valve.
If your steering is easy to operate prior to reaching this position, the pump's output pressure can be reduced.
This requires disassembly of the pump!

I would find a way to get used to stopping your turns prior to reaching this position.

 
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Thanks. It’s idling smoothly at around 700 rpms. If i try to throttle it up, it will still stall or stumble tremendously. Again, no weird noises are made, etc..
 
Post-count wants you to back off the steering when it starts dying? This is ridiculous advice. As Chris says, the issue may be related to the drive if you aren't seeing anything from the inside of the vessel. If it was hydraulics, there would be all kinds of noises coming from the steering stuff. When was the last time the drive was off?
 
Drives were off two years ago. I just bought the boat. All operates well outside of the full stops. I will be removing the drives this winter.

one point to mention is that the clevis pin came out of the steering actuator in the back of the boat The prior mechanic forgot to replace the cotter pin when replacing the engine. I do notice that the steering wheel is not positioned straight ahead but about a quarter turn off. Not sure if that plays into this.

When taking the drive off, what am I looking for?
 

I don't understand why a member would be threatened by high post counts. The comment is completely uncalled for!

When taking the drive off, what am I looking for?

I too would like to know that since it appears to be the full stop locations that are causing your issue!
 
The steering wheel is off because someone installed a new cable and did not do it properly at the helm....
Based on type it can be easily corrected.
Nothing to do with issue.

Reason for Chris's first response is.

If Gimbal bearing is shot and or if ujoints are shot then turning steering to end of travel may be causing binding putting a heavy load on steering components.

Oh and by the way, how long are you holding steering to end of travel? Many minutes?

PCK always makes posts that dont solve the problem....
Just adds to PC...
 

I don't understand why a member would be threatened by high post counts. The comment is completely uncalled for!

Not threatened. It's that we're all standing here holding our umbrellas over our heads and you come running up, all wet, yelling "It's raining!!" Your idea of what's uncalled for is uncalled for.
 
This is just a suggestion and only throwing it out there for consideration...not as a solution to your immediate problem.
Would you consider converting to hydraulic steering? There are several advantages to it. You would need to do some plumbing but in the end I think you'll find the overall boating experience is much nicer. Do you have single station or dual?

As to your issue with the steering actuator, it would seem that the pressure relief valve on the actuator is not operating. What's supposed to happen is that the valve opens when you're at full turn to spill off the pressure coming from the pump. If it's not working it might be just building pressure such that the steering fluid pump is acting as a brake on the engine at low rpm, such as when docking.
Backing off allows normal return ports to be exposed and pressure drops back, pump spins, engine happy.
Has the boat been sitting for any prolonged period? like for a couple years? May be water settled somewhere and rusted up the spring making it non op or blocking a port.
Have you done anything like flush the steering fluid?
 
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Hi. Drives are off the boat and the u joints and swivels move freely. I have the steering pump off the engine.

have not flushed the system.

Where is the pressure relief valve on the actuator? Is that different from the valve and spring in the pump?

yea boat sat for a couple seasons

any idea what the automotive cross reference for this pump would be? i ordered napa’s 20-7920 but the resivoir covers the rear bottom bolt hole so im not sure if that’s the correct cross reference.

thanks again,
 
anyone one have additional thoughts?

Does anyone have a high pressure relief valve they can sell me? The pump is smooth as could be and no noises.

Also: anyone know of a video somewhere that shows how to replace the actuator? I picked up an almost new on and figure I might as well replace that.

thanks
 
Remove the steering cable , the steering pins, and then bend up the locktabs , remove both bolts, remove steering init
click to enlarge
 
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