1974 85hp evinrude runs great then quits

[Fishin76]

Hello, New guy here.

My 85hp 'Rude runs for about 10 minutes then dies and won't restart until it cools down.

rebuilt the carbs, new fuel, sea foam decarbed, new plugs, everything tight,
tested the ignition switch ( ok) No overtemp horn, (works, not overheating).

I can take the engine cover off and extend the 10 minutes, under power, planed out, and moving 30+ keeping what ever it is from heating up and quiting on me.

Runs on muffs all day long, won't quit in the yard.


Help, Too loud to run without the cover on, Need ideas on what to check and how. I'm new to marine outboards of this size.

thanks in advance.

 

[Challenger84]

Re: 1974 85hp evinrude runs great then quits

I think your flooding the OB with too mch fuel .
It can't burn it all fast enough.

 

[emdsapmgr]

Re: 1974 85hp evinrude runs great then quits

Weak ignition components tend to fail once they reach normal operating temps. You may be losing spark. Check for spark on all 4 plug wires with an inductive timing light once it warms up to the point where it quits running.

 

[Fishin76]

Re: 1974 85hp evinrude runs great then quits

No, Definitely not flooding it, as i had a float and needle problem that was flooding it before. and it runs awesome now, except the ignition problem. When it runs, it runs like a scalded dog. it pushes my 18ft heavy jon with 2 adults 42mph flat out. planes out in seconds.

What component would likely shut off all the plugs at once? Timer base? Stator?

I have a Fluke meter, and have good trouble shooting skills. Where do I start looking and how. I know that I'm loosing spark, no doubt in my mind. it shuts off like using the key. I'll drive it back home and it starts right back up in the yard.

Please provide some direction on what to check. I don't want to throw parts at it, too expensive parts are.

 

[joey nathan]

Re: 1974 85hp evinrude runs great then quits

Fishin,
You're probably going to want a service manual. With your good skills, the manual will walk you through the procedure to fault trace that ignition system. Check out the "Boat Parts & Accessories" link up top here...

 

[Fishin76]

Re: 1974 85hp evinrude runs great then quits

Ok, so I did some tests....

Brown to brown/yellow I got 644 ohms cold, and 750 at temp

sensor 1 to sensor 3 I got 8.2 ohms hot or cold.
sensor 2 to sensor 4 i got 8.0 ohm hot or cold.

i read some where that the sensors should be 10 - 20 ohms? does that mean that 8 is bad?

I warmed it up throughly, never did die. I don't have a DVA adapter, so measuring peak voltage is out.


any thing else i can check while dry docked?

p.s. Local boat mechanic says it sounds like timer base, but said i need to get it to fail then test. Maybe the next step.

 

[Fishin76]

Re: 1974 85hp evinrude runs great then quits - solved

Re: 1974 85hp evinrude runs great then quits - solved

I think I got it licked. Took my son out for a trouble shooting session on the water, and I figured i would take him for a ride at 40+. I left the cover off so what ever it was that was getting hot, stayed cooler longer. It did, got 3/4 of lap around the lake then it gradually slowed and stopped. told my son to put out the trolling motor and head for the dock so we could troubleshoot it hot.

I tried to start it again, and something different this time. The starter wouldn't turn, then I noticed the starter solenoid wasn't clicking. I let the motor sit while we were puttin in to the dock. when we got there, i tried it again. Started right up. After getting it on the trailer, i felt the solenoid and almost burnt my fingers.

At this point, I'm wondering if a failing starter solenoid can stop the engine once running.


Can some one verfiy?

 

[emdsapmgr]

Re: 1974 85hp evinrude runs great then quits

Unlikely the hot starter solenoid has anything to do with the ignition problem. The starter and charging system are separate from the ignition system. There is also the possibility that the engine is overheating. If you can borrow or rent a laser temp gun, you can see if it is running normal temps or if it is overheating. A severe overheat can cause the engine to slow down, even temporarily lock up.

 

[Fishin76]

Re: 1974 85hp evinrude runs great then quits

Lets say for arguments sake that it did overheat. What should I do now? what damage could, would it have done?

I know to now check the impeller, but besides that.

 

[ezeke]

Re: 1974 85hp evinrude runs great then quits

Typically, overheat blows the head gaskets and, possibly, the exhaust gaskets. If the temperature gets high enough to burn the engine paint, it can also damage the ignition components.

Good shop practice is to replace the cylinder head gaskets after an overheat and re-torque the cylinder heads after they seat.

 

[bigpoppakdog]

Re: 1974 85hp evinrude runs great then quits

Been there done that!

 

[Fishin76]

Re: 1974 85hp evinrude runs great then quits

No blown head gaskets, no burnt paint. started right back up after the starter solenoid cooled down..

So you tell me, overheated, or not?. warning horn works, tested recently, NO HORN went off.

 

[fdmsiv]

Re: 1974 85hp evinrude runs great then quits

Drop the lower unit and check your water pump.

Pull and test thermostat.

Did you test your over heat horn, the switch, or both?

Is the primer bulb deflated when the engine dies?

 

[whit71]

Re: 1974 85hp evinrude runs great then quits

Is it peeing water? if so dosent sound like its over heating not familar with this engine, but typically if the coil goes bad they will heat up and stop working is the solenoid next to the coil? Sounds like you may have a short in the electrical system check for melted insulation on the wiring or any bare wires/connectors. Good luck

 

[mrcj001]

Re: 1974 85hp evinrude runs great then quits

Check the power pack............

 

[Fishin76]

Re: 1974 85hp evinrude runs great then quits

Horn was tested, not the sensor. looks to be epoxyed to the head? pushed a pin thru the wire and grounded it, horn went off.

No tell-tale on this motor, but water escapes from the exhaust pressure relief ports good, (maybe too good?) Heads stay cool on muffs while testing on land. water is pumping from somewhere, (or getting push thru by the hose, doubtful as I never see water from the relief ports with out the motor running.)


Primer bulb was full and couldn't squeeze it, I already had and fixed the fuel delivery problem by replacing some hose clamps, and rebuilding the carbs 2 weeks ago.

I've ohm tested everything I could hot and cold.

stator charge coils ohm'd out at 644 cold and 750 at temp

timer base ohm'd out at around 8.5 ( 1 to 3 and 2 to 4)

I don't have a DVA, so it's anybody's guess on voltage, but i have not had a dead battery yet. (not that I've run it long enough to drain one, I run 1000cca starting battery)

 

[AlTn]

Re: 1974 85hp evinrude runs great then quits

I think you've answered your own question...it's time to get a dva adapter for your fluke and go to cdi website for testing procedures....someone posted a listing for one ~ $30...as you've stated " hit or miss gets expensive"

 

[Fishin76]

Re: 1974 85hp evinrude runs great then quits

If it's cheaper to buy the components, I can assemble the DVA myself.

On the water pump, Previous owner installed new impeller. I tested tonight, took the entire vernatherm housing off and the diverter. Ran just long enough on muffs (seconds) to see the water exit the block drain on the right side of the thermostat housing plate mounting surface. How hard is the water supposed to exit?

reinstalled the thermostat housing plate and ran again. water now exits both heads. (mind you, I ran the engine for seconds, just long enough to verify decent flow.) Flow seemed ok, not shooting out of the heads, but a decent garden hose flowrate from each side.

In the process of doing this, I learned a few things.

One, NEVER run your engine without something to restrict flow from the water pump.

The engine depends on that diverter and spring to act as a restriction so that the block fills with water completely. Without it, the water just runs out the heads and drains back to the pump, where it is semi recirculated. ( people that installed a tell-tale from the top cylinder made a wise decision. if you have water there, the diverter has not disintegrated, and the vernatherm is not stuck open.)

Two, Never run your engine without a vernatherm unit installed, even if it doesn't work.

This is because when the vernatherm opens it vents all water back to the lake and can cause the block not to fill with water to the upper cylinders. even with a vernatherm that doesn't work, water can circulate in the mid section, and cool the exhaust reliefs like normal. the small loss of water at the exhaust reliefs allows the water pump to bring in new cool water, just not alot of it. (not enough to keep the engine temp cool and stable at running speeds, anyway). Not having the vernatherm installed looks like it can overheat your engine, but just the top two cylinders on a V4.

I think I caught mine not opening when it needed to. The pintle on the vernatherm was bent, stuck, and did not want to come out of the housing either. I pulled it out with a pair of pliers. I made a new pintle out of a aluminum rod of almost the same diameter as the pintle. The pintle was brass. I ground my new pintle to just a little longer than the original to hold the vent open and provide extra cooling water to mix with the warm recirculated water from the diverter at the pump.

This is not a good solution, but I need my boat for the weekend, and expedited shipping is expensive.

Just thought i would share.

 

[Fishin76]

Re: 1974 85hp evinrude runs great then quits

Can anybody tell me a quantity of water per minute that the pump should put out unrestricted?