problem with Evinrude 60 2 stroke

[tunaticer]

Time for the brains trust to come into play.

Got a Evinrude 1992 60hp 2 stroke remote controlled motor that is playing up.
Starts fine, idles perfectly, runs nicely for the first minute or two up to full revs (reaches 5700rpm max) then two cylinders shut down. drop back to 2000rpm and it runs perfectly but will not accelerate again and drops the 2 cyls again. Switch the engine off and restart it straight away and it will repeat the run well cycle for a minute or two then shut down two cyls again.

So far I have replaced plugs with Champion QLV77JC4 plugs, replaced fuels filters, Checked for air leaks in the fuel lines, replaced the impellor and thermostat (in case it is a heating problem) and checked idle timing.

What else should I be checking?
Does this motor have a SLOW protection system being 2 stroke carby model? If so how does that react when it cuts in?

I notice it has an electric fuel pump system, are these prone to high rev failure?

Can a CDI power pack behave like this?

[39NESP]

had same prob turned out to be power pack
cheers snap

[tunaticer]

Thanks snap, I was suspect of that.

[captain rednut]

disconnect the brown wire on the head for a test, it may be overheating or a faulty power pack or temp sensor??

[tunaticer]

disconnect the brown wire on the head for a test, it may be overheating or a faulty power pack or temp sensor??

This test should deliver what result??
If the unit is faulty it should do what when run?
If the unit is ok it should deliver what result when run?

[cormorant]

We are talking on the water under load or on muffs?

Get coils checked as well before buying a power pack. Coils can overheat but then work when they come back to temp. Is it always the same to cylinders? Confirm if it is spark it is losing.

Waterflow blockage in one side of head,

Simple as a sticking float , needle and seat in a carby from gummy fuel?
Blocked fuel filter?
Fuel hose affected by premium or ethanol fuel collapsing its internal layer. Got another fuel line to try.? If fuel bulb soft or hard and does motor pick up if you squeeze the primer bulb?

Ifs the choke turning on? Be it electonlic or butterfly - often hard to tell if excces or fuel , or no spark etc?

Check main carb butterflys are synchronised and all solid not turnig on the shafts

Have seen sort of similar with both fuel pump issue and also with a stuffed reeds

Flush out carby bowls in case high revs are lifting crap up to jet.

Waterflow blockage in one side of head if has more than one sensor- not usually on that size,

Failing rectifyer ot reg on charge circuit as I think they take revs fron that circuit so may be thinking it is hitting rev limiter if that model had one.

Start with the simple easy things you understand and see if you can narrow it down.

Not shorting a wire in the cotrol box as you push throttle forward or under the cowl? Check wires are routed correctly.

[testlab]

Is it the VRO model?

I think they did have a limp home mode in the early 90s. There were a few variations around those years. I remember fixing a mates one (as home garage mechanics) that had warning problems but I think it may have been a later model (94 or 96 maybe) - but it definitely had a limp home mode that acted just like what you are describing.

With his the warning system made rapid beeps for a VRO failure, a beep every now and then for low oil tank level and continuous tone for overheat. But the warning buzzer was cactus (we later found a dodgy crimp).

If I remember when we simulated VRO and overheat the motor went into limp home mode. The power pack controlled the buzzer and should have sent the right number of beeps. I take it your buzzer is not sounding when it won't go past 2000 or you would have mentioned it. Is the buzzer working? Maybe it isn't.

Warning... If I remember correctly the squirter runs on the outlet of the water pump before it goes into the block/head. If you have a dodgy thermostat or blockage in the galleries it could be overheating with plenty of water at the tell tale.

Ground the brown wire that comes out near the thermostat and with the ign on it should sound continuously. If not the warning circuit is not working and its harder to diagnose. If you are certain it is not overheating then disconect the brown wire and see if you can run it at speed without going into limp mode.

If it still "goes limp" then it could be the VRO oil pump warning causing it.

If it runs ok then dodgy temp sensor (assuming its not overheating).

We spent a whole afternoon trying to test this (at the ramp) without stuffing the motor. In this case the VRO pump was blocked and we wound up doing a premix conversion.

Hope this helps. Just be sure its not overheating and check that warning buzzer before blasting about with it disabled.

PS: Its xmas night plus trying to remember back around 10 years, so sorry for disjointed explanation. His motor was dying like yours. First we found the warning buzzer problem, which helped us find the VRO problem.

[tunaticer]

We are talking on the water under load or on muffs?

Have seen sort of similar with both fuel pump issue and also with a stuffed reeds

Flush out carby bowls in case high revs are lifting crap up to jet.

Waterflow blockage in one side of head if has more than one sensor- not usually on that size,

Failing rectifyer ot reg on charge circuit as I think they take revs fron that circuit so may be thinking it is hitting rev limiter if that model had one.

Start with the simple easy things you understand and see if you can narrow it down.

Not shorting a wire in the cotrol box as you push throttle forward or under the cowl? Check wires are routed correctly.

This problem occurs under load not on muffs.

The motor runs perfectly for one or two minutes then drops two cylinders instantly.....do not know which two cylinders as we are underway on the river.

If it was reed valves the motor would not reach high speed then shut down

Checked the control box for wiring problems none found

Any test available for the fuel pump at high speeds?

All water galleries seem to flow well from what I can make out.

If i simply disconnect the temp sensors will that let the motor fire? Will it damage the ignition system?

Never run ethanol fuels and primer bulb in normal condition. When the cyls shut down the primer bulb in not deflated and still fairly firm......possibly indicating that the electric fuel pump is not sucking at higher demand levels???
Fuel lines and filters in good condition. can not detect any fuel leaks or air sucking in the connections or lines.

The part that stumps me is why when it drops the two cyls if you shut down and restart immediately it does not go into a dropped cyl mode for a few minutes? That indicates to me it is not heat related because these sensors will not have had any change in temps of water or metals.

This SLOW system this motor has........does it shut down two cyls like this or throttles the motor back to just above idle firing on all pots? I figure that the SLOW system would be usually triggered by the temp sensors on a 2 stroke of this vintage.

Thanks for your input Cormorant.

[tunaticer]

Is it the VRO model?

I think they did have a limp home mode in the early 90s. There were a few variations around those years. I remember fixing a mates one (as home garage mechanics) that had warning problems but I think it may have been a later model (94 or 96 maybe) - but it definitely had a limp home mode that acted just like what you are describing.

With his the warning system made rapid beeps for a VRO failure, a beep every now and then for low oil tank level and continuous tone for overheat. But the warning buzzer was cactus (we later found a dodgy crimp).

If I remember when we simulated VRO and overheat the motor went into limp home mode. The power pack controlled the buzzer and should have sent the right number of beeps. I take it your buzzer is not sounding when it won't go past 2000 or you would have mentioned it. Is the buzzer working? Maybe it isn't.

Warning... If I remember correctly the squirter runs on the outlet of the water pump before it goes into the block/head. If you have a dodgy thermostat or blockage in the galleries it could be overheating with plenty of water at the tell tale.

Ground the brown wire that comes out near the thermostat and with the ign on it should sound continuously. If not the warning circuit is not working and its harder to diagnose. If you are certain it is not overheating then disconect the brown wire and see if you can run it at speed without going into limp mode.

If it still "goes limp" then it could be the VRO oil pump warning causing it.

If it runs ok then dodgy temp sensor (assuming its not overheating).

We spent a whole afternoon trying to test this (at the ramp) without stuffing the motor. In this case the VRO pump was blocked and we wound up doing a premix conversion.

Hope this helps. Just be sure its not overheating and check that warning buzzer before blasting about with it disabled.

PS: Its xmas night plus trying to remember back around 10 years, so sorry for disjointed explanation. His motor was dying like yours. First we found the warning buzzer problem, which helped us find the VRO problem.

Thanks for the reply Testlab.
This motor is not a VRO model.
It has not warning buzzer that is operating.
This motor runs on 50:1 premix fuel.
The telltale water line comes from the block side of the thermostat housing at the very top of the motor so it should be getting good water through all jackets and galleries to reach there.
New impellor and thermostat fitted.
Can not detect any fuel supply problems at idle (starts and idles perfectly runs for one to two mins then drops two cyls completely shudders badly until you drop back the throttle and revs stabilise near 2000rpm and fires on all pots)

[Fed]

I'd put the proper fuel pump on it.

[testlab]

Thanks for the reply Testlab.
This motor is not a VRO model.
It has not warning buzzer that is operating.
<snip>
Can not detect any fuel supply problems at idle (starts and idles perfectly runs for one to two mins then drops two cyls completely shudders badly until you drop back the throttle and revs stabilise near 2000rpm and fires on all pots)

Still sounds like it is the power pack cutting it out. Especially since it resets and runs OK again after the ign is turned off and back on again.

I'd still be thinking its the temp sensors, it may be an intermittent short. Does it have a warning buzzer at all, if so does it work (ground the brown wire to test it).

One other thought... does it have a reverse gear interlock switch that tells the power pack to limit the speed (I know the older omc motors had mechanical interlocks). Is it intermittently shorting?

[tunaticer]

I'd put the proper fuel pump on it.

It is the original fuel pump on this motor, serial numbers align with the data sheets.

[tunaticer]

Still sounds like it is the power pack cutting it out. Especially since it resets and runs OK again after the ign is turned off and back on again.

I'd still be thinking its the temp sensors, it may be an intermittent short. Does it have a warning buzzer at all, if so does it work (ground the brown wire to test it).

One other thought... does it have a reverse gear interlock switch that tells the power pack to limit the speed (I know the older omc motors had mechanical interlocks). Is it intermittently shorting?

Running a test on the temp sensors in the morning, I am unsure about it's condition.

Where is the buzzer alarm situated on these motors? I have trawled through the motor, remote control and the service manuals but I cant find mention of where this item is located. That being said, I do not hear too well and detecting an alarm over the motor noise would be difficult for me. If I knew where it was I could rig a lamp to show it is activating.

Reading through a zillion pages today of the SLOW engine management system I gather the motor shakes like hell as if dropping two cylinders to drop the rpms and fuel being burnt and temp being raised. I sort of had stuck in my head it would simply cut back on the rpms without shutting down two cyls though??

Tomorrow is testing day for everything electrical.......Pretty well convinced now it is not a fuel problem. Either temp, temp sensor or power pack.

[Spaniard_King]

Alarm buzzer will be in the control box, good chance its not functioning with that age on it.

Might be worth the effort to look into the buzzer when ya sort out the rpm limiting issue,

I think your on the right track tho.... hook a timing light to the plugs and see if you can notice if the spark is being restricted when you replicate the fault.

[Fed]

I notice it has an electric fuel pump system

Didn't know OMC ever used one on carby motors, sorry.