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Problem with OMC 5.0 EFI engine (see video)

Why were you taking the adapter apart? the thermostat is on top. You can probably buy a replacement instead of welding it. Good luck.
 
I didn't! I have replaced the thermostat but when I should tighten the screw for the thermostat housing to the adapter the screw bracket was broken. So i need to weld it back again. I think it's hard for me to find a new "adapter" here in Sweden. However the adapter is attached with a Torx screw. But it's stuck so I think i will weld in the boat instead of the garage. I just must find a guy that can help me with that, but that shouldn't be so hard.
 
Hey. I just had the same issue as this Thread started. I would rev up to 2600 and once it got there it would just twitch and is now in slow mode. Did your fix work by cutting your wires?
 
This post has saved my summer lol. My boat was doing the same as the original posters boat was doing. Cutting the wire does work (Tan/brownish with a black stripe). I have a 94 Four Winns Horizon with a 5.8L EFI OMC engine. The engine was in SLOW mode for a reason though. I kinda suspect low oil pressure. At idle when warm my oil pressure jumps between 0 and 5 psi and goes to 40 when above idle (not sure how accurate my gauge is though). I have had my problem since July of 13 and my marina mechanic wasn't able to fix it. I'm not recommending cutting the wire to anyone, but I was desperate for a fix. Thanks for all your help guys.
 
John Bachman said:
This post has saved my summer lol. My boat was doing the same as the original posters boat was doing. Cutting the wire does work (Tan/brownish with a black stripe). I have a 94 Four Winns Horizon with a 5.8L EFI OMC engine. The engine was in SLOW mode for a reason though. I kinda suspect low oil pressure. At idle when warm my oil pressure jumps between 0 and 5 psi and goes to 40 when above idle (not sure how accurate my gauge is though). I have had my problem since July of 13 and my marina mechanic wasn't able to fix it. I'm not recommending cutting the wire to anyone, but I was desperate for a fix. Thanks for all your help guys.
Click to expand...


As I wrote in my original post. I still have my gauges to go by. I suspect a short in the wire harness thru the engine block.
Mine was not an oil pressure or temperature issue. I bypassed both sensors and still had the same problem. Cutting the wire to the computer eliminated the problem. I bet if you run a new wire to the sensors it would be fine.. Have fun boating.
 
Hy Guys !
,. this is my first post here,.
I've also a OMC 5.0 EFI engine.. and (what a pitty),. exactly the same issue,.
we can run up to 2800rpm,. anything above will result into something like that sounds like an rpm limiter...
what we've done so far,.
.) air bypass valve,. (difficult to get),. but we managed it to buy one
.) ignition cables
.) spark plugs
.) distributor cap and finger,
.) fuel filter

karistos : could you explain where did you cut wich wire,. a litte bit more detailed?,.

thank's in advance !
 
karistos said:
RicardoMarine said:
By 1994, this should be Volvo Penta, no longer OMC.

Start by getting the serial number, and look for Volvo Penta data by serial or model number.
Perhaps order an OEM service manual for this particular engine model.
Click to expand...

The boat is 1994 but the engine was made in 1993 Model # 50FAPLJVN
Click to expand...

I only mentioned this due to the pre-1994 OMC Cobra drive being a Dog Clutch -vs- the 1994 and later Volvo Penta drives being Cone Clutch.
The OMC Cobra dog clutch drive requires the ESA (electronic shift assist), whereas the Volvo Penta drive does not!

If not familiar with the difference between the two drives (OMC Cobra vs Volvo Penta SX)...... give this a try:
(assuming that the boat is on a trailer... with the engine OFF)

While in either gear, see if the propeller will rotate in the direction of the gear selected.
If you can hear the ratcheting sound of the Dog Teeth, then you'll have an OMC Cobra Dog Clutch drive, and the ESA system.

If you are not able to hear the ratcheting sound, then you'll have a Volvo Penta cone clutch drive, and no ESA system.



If you actually have an OMC Dog Clutch drive, then you'll also have the ESA system, of which may or may not play a role in your issue.


.
 
This issue bothered me for a year before I found this post, so I want to see others get help from it.
Mine is the 5.8l EFI, but they should be close to the same. If you are in the boat facing the engine,
the ECA module is on the left hand side on top. It has a rectangular boot covering the wires going into the module.
If you look at the picture in the original post, it shows the MAP sensor. Just to the left of that is the ECA module.
Pull the rectangular boot back to expose the wires, and look for the tan/brownish wire with a black stripe and just cut it.
If you're worried about it you can always reconnect it later. I cut mine a month ago and have had no negative issues since.
I'm not a mechanic, just trying to help.
 
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