5.8 omc loosing power

[duckstar]

After i warm up my 93' 5.8 omc at the dock she runs smooth until i put it in gear, it starts to misfire and run rough,and eventually loses power trim guage is bouncing all over the place can't figure it out any help would be appreciated THANKS!

 

[HT32BSX115]

Re: 5.8 omc loosing power

After i warm up my 93' 5.8 omc at the dock she runs smooth until i put it in gear, it starts to misfire and run rough,and eventually loses power trim guage is bouncing all over the place can't figure it out any help would be appreciated THANKS!

Howdy,


Your problem sounds a lot like an electrical problem.

A little more info will help. Model number, EFI or carb, salt or fresh water......

Does it sit in a marina in the water or do you park it in a dry garage etc?



To start, check all electrical connections (power AND ground connections) especially the battery connections.

Because the trim gage is "jumping" around, it's indicative or a poor connection someplace.



Regards,



Rick

 

[duckstar]

Re: 5.8 omc loosing power

thanks rick its a93' 5.8 efi that sits in a marina in salt water, the trim gauge is the only gauge jumping around ,other gauges are fine, hope this helps steve!

 

[alldodge]

Re: 5.8 omc loosing power

Hi Steve
Sounds like you have an electrical connection problem. Start with grounds from the battery, to the engine block, to behind the dash and don't forget the harness connector to the engine. Don't just look, take the cables off and clean, unplug the connectors and check for corrosion. Most corrosion issues all come back to unseen issues with a connection

 

[bruceb58]

Re: 5.8 omc loosing power

Your trim gauge bouncing around is likely the trim sender that's bouncing and has nothing to do with your misfire problem, especially if its the only gauge bouncing. Those senders are notorious for this.

A bad ground behind the dash won't have anything to do with the misfire since that ground has nothing to do with the engine at all.

As far as misfire after you shift, unplug the ESA and try it. Just be careful as you may not be able to shift back into neutral so be ready to just turn off the engine with the ignition switch.

 

[HT32BSX115]

Re: 5.8 omc loosing power

93' 5.8 efi that sits in a marina in salt water

Oh boy! the "perfect storm" of an electronic OMC (or any older electronic engine!)

You don't really have an ESA (module) per se'

There is an interrupter though and it does it through the ECM using a single switch.
From: BRP -- Parts Catalogs

0987587 SWITCH, Shift

Here's why it's important to know the exact model number.

For a 93, it could be one of 11 models ( dog-clutch and cone-clutch) OR it could be a 92 model (1 of 6models both Dog and Cone) OR, you could have a "franken-boat" with a combination of the above! (unlikely though)

The "Dog's" use an ESA module usually controlled by 2 switches. The EFI models, use a single switch that simply tells the ECM you're trying to pull it out of gear.

Any intermittent electrical problem is usually loose connections, chafed wires, poor and/or corroded connections, bad or mal-adjusted switch(es) etc.

Like bruce said though, the jumping trim gage is probably unrelated to the running problem.

What model (exactly) do you have?

 

[bruceb58]

Re: 5.8 omc loosing power

Rick, there are 1993 5.8s that used ESAs still but you are probably right in that the EFI ones don't. They would only have one switch since the overstroke switch hadn't been used anyway for a few years.

OMC Stern Drive Engine Wire & Shift Module Parts for 1993 5.8 L 584APLJVB Stern Drive

 

[HT32BSX115]

Re: 5.8 omc loosing power

Rick, there are 1993 5.8s that used ESAs still but you are probably right in that the EFI ones don't. They would only have one switch since the overstroke switch hadn't been used anyway for a few years.

OMC Stern Drive Engine Wire & Shift Module Parts for 1993 5.8 L 584APLJVB Stern Drive

Yeah, I think the 93 EFI's were "Cones". There's an interrupt switch, but I think the ECM did the "stumbling" if it was really a "stumble" at all.......I think the newer ESA's (dogs) had a timer built in so it only "stumbled" for a second or 2 max.....so they eliminated the over-stroke switch.

 

[bruceb58]

Re: 5.8 omc loosing power

Here is the latest 5.8 with EFI. Looks like a dog clutch
1993 OMC 58FAPRJVN hp L Stern Drive Parts

 

[HT32BSX115]

Re: 5.8 omc loosing power

Here is the latest 5.8 with EFI. Looks like a dog clutch
1993 OMC 58FAPRJVN hp L Stern Drive Parts

Yeah. So some EFI's are Dogs, and some are Cones. IN 93...... (I made a rash assumption that ALL EFI's were cones!!)

So, Duckstar.......see why we need to have that model number in the first post?

We spin our wheels with conjecture trying to figure out what you have!

We still don't know if you have a dog-clutch drive WITH an ESA or a Cone-Clutch drive with an (interrupt) ECM. Or vice versa. Or neither!
the 58FAPRJVN engine and drive is dog with the ESA "built-in" to the ECM........

The problem and fix may be literally "the same" but it sure helps to know exactly what you have so we can all look at the right circuit diagram.....

 

[duckstar]

Re: 5.8 omc loosing power

yes the model #is 58faprjvn thanks for your interest any help is appreceated.steve

 

[HT32BSX115]

Re: 5.8 omc loosing power

After i warm up my 93' 5.8 omc at the dock she runs smooth until i put it in gear, it starts to misfire and run rough,and eventually loses power trim guage is bouncing all over the place can't figure it out any help would be appreciated THANKS!

OK,


Well,

You have a dog clutch Cobra (according to your model number)

You also have an ESA that should ONLY actuate when you go from FWD or REV TO Neutral.

It should NOT EVER actuate when going INTO gear. The ESA will cause the engine to "stumble" any time it's actuated.

If it does when going to FWD or REV, then the lower shift cable OR the actual shift mechanism (sliding shift dogs etc) are binding and causing movement of the shift interrupter housing.

See BRP -- Parts Catalogs , Parts Catalog, Shift Bracket (#22 in the illustration ) for your model.

Regards,


Rick

 

[jerryjerry05]

Re: 5.8 omc loosing power

The shift mechanism could be binding,the bellcrank hanging up,the exhaust flapper fell down into the shift rod?
The cable binding.
The shift modual bad.

 

[duckstar]

Re: 5.8 omc loosing power

rick I tried to move the lever manually on the switches that cuts the motor out when shifting into gear, one made the motor stumble, the other did nothing when i manually pushed the lever over,could that be a bad switch .steve!

 

[duckstar]

Re: 5.8 omc loosing power

rick I tried moving the lever over that stumble the motor manually , one lever stumbled the engine the other did nothing when i pushed it over .could that be making the motor run rough after i put it in gear? thanks steve!

 

[bruceb58]

Re: 5.8 omc loosing power

The second lever is the overstroke switch and it actually prevents the engine from stumbling. It is used to detect when you have drive all the way in gear and prevents any stumbling.

 

[HT32BSX115]

Re: 5.8 omc loosing power

Steve,


I looked a little closer at that shift bracket for your model...(assuming someone hasn't modified your setup on the last 20 years) .......The shift actuator (#22) is what should be moving when you move your shift lever from FWD or REV to Neutral.

When you move it INTO gear, it should NOT move enough to actuate the ESA (actuating #26, the Shift Cutout Switch)

#28, is the "Neutral Drive" switch. Bruce, is that what you're calling the "over-stroke" switch? I wonder if they just "renamed" it?

Steve, In any case.........if the shift actuator is moving enough to operate the switch when you shift INTO gear, either the "Shift Interrupter Spring" (#17) has become weak (which is unlikely) or there's some binding in the either the lower shift cable or the actual sliding shift dogs/mechanism.

 

[bruceb58]

Re: 5.8 omc loosing power

I think he needs to post a picture of his engine where the shift bracket is just to make sure.

I am wrong about the overstroke switch. I posted without remembering we are looking at a FI engine as well as it being a 93 model. Neither have overstroke switches.

The neutral switch must be used by the fuel injection to set the idle speed. I doubt its for shifting but probably need to see a manual.

 

[HT32BSX115]

Re: 5.8 omc loosing power

Actually I meant #28 in the above picture. I'll bet the cable or mechanism is jamming just enough to move the shift actuator when going into gear.....

 

[bruceb58]

Re: 5.8 omc loosing power

Easy to test...just unplug the switch and see if it still runs rough. Just may have to turn off the motor to get it back into neutral.