Help! Bought a 1993 Four Winns W/ 5.0 OMC Cobra Motor and Drive - Losing power after crusing

[cameron92]

Video here

See the video link above. just bought this boat, guy assured me on God that all was good as I was bringing my 1.5 year old out.

I'm not sure what's happening. I'll be crusing along and all of a sudden the rpms on the gauge will rise, then the boat comes to a stop, rpms drop (I'm not touching the lever).

It'll also do the same thing if I give it full throttle. Also when taking off after it happens sometimes there's a faint bang.

Spun Coupler? Misaligned shift cable? Engine issue? I'm lost. How do I test.

Changed to old prop seller gave me, same issue. Drained drive, a bit of metallic on the plug but no shavings.

 

[Mc Tool]

The engine rpm's are not rising when the gauge sez that they are....apart from that ...beats me . You'd have to think that it might be an ecu/ignition issue

 

[cameron92]

The engine rpm's are not rising when the gauge sez that they are....apart from that ...beats me . You'd have to think that it might be an ecu/ignition issue

I hope so. I can deal with that. I've been reading maybe an engine coupler or dog gears.

 

[Lou C]

I’m wondering if the tach is defective and shorting out the ignition. I’d try disconnecting the wire from the ignition to the tach at the tach and see if that’s it. Ford 5.0 EFI?
Post up pix of the engine & drive so we can see what you have. There were many variations in these and you have to know what you have to have a chance of fixing it right. 1993 was the end of the dog clutch Cobras but OMC made their own cone clutch model which is different from the joint venture models made with Volvo.

 

[Mc Tool]

I’m wondering if the tach is defective and shorting out the ignition. I’d try disconnecting the wire from the ignition to the tach at the tach and see if that’s it. Ford 5.0 EFI?
Post up pix of the engine & drive so we can see what you have. There were many variations in these and you have to know what you have to have a chance of fixing it right. 1993 was the end of the dog clutch Cobras but OMC made their own cone clutch model which is different from the joint venture models made with Volvo.

Yeah Im thinkin the engine seems to loose power (and revs ) at the same time the tach climbs up ...and its unlikely the two are not connected ...I dont know what triggers the tach but it seems like something is messing with the ignition timing causing loss of power and also making the tach tell lies ...mmm. I just dont know enough about them but Im trying to think how I would "logic" it out if it were mine

 

[tpenfield]

Disconnect the tachometer and see if the problem goes away. Also remember that you bought a 33 year old boat. There could be all kinds of issues, that the seller & God don't know about.

 

[Lpgc]

If it's EFI will it have a crank position sensor that could be defective?

I don't know how the rpm tachnometer at the helm (on the dashboard) connects to the EFI setup but regardless of if it gets it's signal from the ECU or from the coil, if the ECU uses a crank sensor that isn't reading correctly the ECU could read incorrect rpm and (if the ECU also controls ignition) this could cause both the higher rpm reading and drop of power (if there are more pulses at the coil than there's supposed to be ignition timing must be wrong).

I have a 96 Four Winns Sundowner with carb'd 5.0, it had problems with the ignition due to low voltage to the coil. Power to the coil came from the engine up to the ignition key and dead man kill switch then back to the engine, the voltage drop was somewhere along that routing, I fixed the low voltage problem by wiring in a relay to switch ignition at the engine so the ignition key only had to power the relay.

 

[cameron92]

What would explain the bang? Anyone have experience with engine couplers going out? I'm debating pulling the motor.

When I was backing it off the trailer yesterday after changing props the belt started squealing. Not sure which belt, assuming alternator. Also smelt burning rubber.

I know problems are bound to arrise. This seems to consistently happen after approx 3-5 mins of cruising (like something heats up)

 

[Lou C]

Yes if it has a crank sensor for EFI, a failing crank sensor could do something similar, on my old '98 Jeep 4.0 when the crank sensor was starting to fail, one sign was the tach and idle would drop and recover, eventually that turned into a higher speed miss, followed by a reluctance to start, ending in a refusal to start. It did not set a code till the sensor totally failed.
I have a 1988 OMC factory shop manual but this model is so much newer that there's nothing that's similar. In the vid it looks like a Ford 5.0 with the EFI system, so I can't help there. If it was the older models with carbs and points, oh yeah I know THOSE things quite well lol!
Post up pix of the engine and drive.
A bang if you have a dog clutch Cobra might be wear on the clutch dogs or fwd gear causing it to slip out of gear under power, but it could be a lot of other things....
Here's a guess on what you might have....

https://www.marineengine.com/parts/omc-parts/omc-boat-parts.php?year=1993&hp=5.0&model=50FAPRJVN

EFI Ford engine, and the last of the Cobra Dog Clutch drives....
the Cobra dog clutch part I am familiar with and they require a good shift cable in good adjustment to last. I have had the same cable on mine all these years (owned 24 years) and it needed adjusting when I first got it in 2002 and then again about 10 years later, I learned how to do the tricky adjustment myself, not really hard. It has required very few repairs, over the years in salt water use and moorage. A few seals, bellows 2x, gimble bearing once, and I rebuilt the trim rams a few years ago.
You need a good OMC mechanic who knows about the EFI engines, I don't, and if I had one that was acting up, due to most of the parts being NLA, I'd simply convert it to a 4bbl carb and Davis Unified Ignition distributor, that eliminates all the headaches of NLA OMC EFI and electronic ignition parts.

 

[cameron92]

I’m wondering if the tach is defective and shorting out the ignition. I’d try disconnecting the wire from the ignition to the tach at the tach and see if that’s it. Ford 5.0 EFI?
Post up pix of the engine & drive so we can see what you have. There were many variations in these and you have to know what you have to have a chance of fixing it right. 1993 was the end of the dog clutch Cobras but OMC made their own cone clutch model which is different from the joint venture models made with Volvo.

Yes EFI Model 50FAPRJVN

 

[cameron92]

Yes if it has a crank sensor for EFI, a failing crank sensor could do something similar, on my old '98 Jeep 4.0 when the crank sensor was starting to fail, one sign was the tach and idle would drop and recover, eventually that turned into a higher speed miss, followed by a reluctance to start, ending in a refusal to start. It did not set a code till the sensor totally failed.
I have a 1988 OMC factory shop manual but this model is so much newer that there's nothing that's similar. In the vid it looks like a Ford 5.0 with the EFI system, so I can't help there. If it was the older models with carbs and points, oh yeah I know THOSE things quite well lol!
Post up pix of the engine and drive.
A bang if you have a dog clutch Cobra might be wear on the clutch dogs or fwd gear causing it to slip out of gear under power, but it could be a lot of other things....
Here's a guess on what you might have....

https://www.marineengine.com/parts/omc-parts/omc-boat-parts.php?year=1993&hp=5.0&model=50FAPRJVN

EFI Ford engine, and the last of the Cobra Dog Clutch drives....
the Cobra dog clutch part I am familiar with and they require a good shift cable in good adjustment to last. I have had the same cable on mine all these years (owned 24 years) and it needed adjusting when I first got it in 2002 and then again about 10 years later, I learned how to do the tricky adjustment myself, not really hard. It has required very few repairs, over the years in salt water use and moorage. A few seals, bellows 2x, gimble bearing once, and I rebuilt the trim rams a few years ago.
You need a good OMC mechanic who knows about the EFI engines, I don't, and if I had one that was acting up, due to most of the parts being NLA, I'd simply convert it to a 4bbl carb and Davis Unified Ignition distributor, that eliminates all the headaches of NLA OMC EFI and electronic ignition parts.

Good guess! Ya I posted in an OMC group on Facebook and had 3 or 4 people say engine coupler which is why I'm leaning that way. Might see if I can get an eye on it with my 360 camera, unless it's buried under a housing then the only way to check would be to pull the motor.

The RPM gauge is wierd because someone mentioned it earlier, the engine isnt revving to 6000, the gauge is just acting up.

 

[Lpgc]

If it was the coupler wouldn't the actual engine revs climb while boat speed dropped off? In the video the tach shows the revs climbing but listening to the engine the actual revs drop. If the actual revs drop the boat speed will drop off but there's a difference between speed dropping because revs dropped versus speed dropping because of a coupler problem, one is engine related the other is coupler related.

 

[Lou C]

Yes it could be that, but could also be a slipping prop hub, try marking the hub of the prop and see if it's slipping under power.
You cannot see the coupler from the engine compartment, the bellhousing covers it totally but one thing you can do, is pull the outdrive and inspect the splines in the coupler that will be visible through the bellows area (bright LED flashlight). The splines in the coupler should be well defined and squared off, also look at the splines on the driveshaft. My boat at 38 years old has the OEM coupler still. What makes them last is good alignment and pulling the drive once a season and greasing the splines with spline grease.

This step above is regular maintenance that'd I do on any I/O boat new to me before running it, but I agree with Lpgc above, it doesn't seem likely your problem because of how the tach and engine are acting opposite of what you'd expect. Tach rises like that, engine should be screaming and it's not.
Disconnect the grey wire on the back of the tach, and try again.

 

[cameron92]

Yes if it has a crank sensor for EFI, a failing crank sensor could do something similar, on my old '98 Jeep 4.0 when the crank sensor was starting to fail, one sign was the tach and idle would drop and recover, eventually that turned into a higher speed miss, followed by a reluctance to start, ending in a refusal to start. It did not set a code till the sensor totally failed.
I have a 1988 OMC factory shop manual but this model is so much newer that there's nothing that's similar. In the vid it looks like a Ford 5.0 with the EFI system, so I can't help there. If it was the older models with carbs and points, oh yeah I know THOSE things quite well lol!
Post up pix of the engine and drive.
A bang if you have a dog clutch Cobra might be wear on the clutch dogs or fwd gear causing it to slip out of gear under power, but it could be a lot of other things....
Here's a guess on what you might have....

https://www.marineengine.com/parts/omc-parts/omc-boat-parts.php?year=1993&hp=5.0&model=50FAPRJVN

EFI Ford engine, and the last of the Cobra Dog Clutch drives....
the Cobra dog clutch part I am familiar with and they require a good shift cable in good adjustment to last. I have had the same cable on mine all these years (owned 24 years) and it needed adjusting when I first got it in 2002 and then again about 10 years later, I learned how to do the tricky adjustment myself, not really hard. It has required very few repairs, over the years in salt water use and moorage. A few seals, bellows 2x, gimble bearing once, and I rebuilt the trim rams a few years ago.
You need a good OMC mechanic who knows about the EFI engines, I don't, and if I had one that was acting up, due to most of the parts being NLA, I'd simply convert it to a 4bbl carb and Davis Unified Ignition distributor, that eliminates all the headaches of NLA OMC EFI and electronic ignition parts.

What's the best way to do a shift adjustment, there is a slight grind when first going into gear. Nothing while operating but definitely there upon engagement.

 

[Lpgc]

Is there something (electronic) that monitors engine revs versus drive speed and backs of power when they don't agree? I doubt it but I don't know if the dog clutch drives and EFI engine combination features it. That kind of thing is fitted on modern vehicles to prevent damage to engines/transmissions in case a trans clutch slips.

 

[cameron92]

Is there something (electronic) that monitors engine revs versus drive speed and backs of power when they don't agree? I doubt it but I don't know if the dog clutch drives and EFI engine combination features it. That kind of thing is fitted on modern vehicles to prevent damage to engines/transmissions in case a trans clutch slips.

Ya there's a little microswitch I forget the name of it but when I press it the rpms drop

 

[Lou C]

Yes EFI Model 50FAPRJVN View attachment 417121View attachment 417122

Yep good old Dog Clutch, at least you can get most of the parts for them, unlike the OMC Cone Clutch!
Sorry, the EFI parts electronic ignition parts for that Ford EFI engine, are nearly all NLA. I don't know if any were Ford automotive OEM parts, but if you look in the link to the catalog I posted you'll see what I mean.
In older versions they came with a Holley 4160 marine carb, and a Prestolite points distributor, both of which can be easily maintained.
But that's getting way ahead of the story, because we don't know what's causing your problem YET.
One thing I'd check right away, is the anti siphon valve and the fuel pick up tube. The anti siphon valve can stick or get clogged with crud from the tank, and the pick up tubes sometimes have a screen on the end of them that gets clogged. I just replaced both on my old 1988 Four Winns.

 

[cameron92]

Just found out my power steering pump is bone dry... Was full when I bought the boat. Another issue he's covering up I guess.

 

[Lou C]

Ya there's a little microswitch I forget the name of it but when I press it the rpms drop

What you have is OMC's ESA system (electronic shift assist). What it does is drop your engine idle speed when shifting from in-gear to neutral from about 600 to 450 rpm, that allows the drive to drop out of gear and shift to neutral. If that interrupt switch sticks, it COULD cause symptoms like you see, but it would likely do it right after you shifted into fwd gear.
I did have that problem on mine about 12/13 years ago, the interrupt switch stuck on and it was obvious that the engine was running with like half it's power.....I replaced both switches (older ones had 2 switches) and the ESA Module and no more problems with it.

 

[Lou C]

Just found out my power steering pump is bone dry... Was full when I bought the boat. Another issue he's covering up I guess.

Hope you don't have to replace the steering actuator. I did and it was a 2 day long F-bomb fest, due to access and 2 dang cotter pins that didn't want to move, OH I got it, done but not fun. Had to remove the rear seats and the whole exhaust system. I now have a rebuild kit for the the older style control valves, yours is newer so it's different. Check all around the p/s hoses to see where the leak is. Might be a simpler solution lol.