first outing not so good

took the boat out yesterday , launched it , started up the 1985 Evinrude 40 , ran real good at idle , water pump peeing real good …. idled out thru idle zone , just as we got to open water , we got the alarm squeal…… constant, loud , squeal , water pump appeared to be doing fine…. NO VRO on this one that I can see and no oil tank . weren't sure if it was a overheat squeal or not so I put it wide open for a second to see what it would do and it wouldn't go any faster . It had shut itself down to about 2000 rpms as it should do for safety purposes not to ruin motor ...… the head felt hot , the entire engine felt hot , so we idled it back to shore and loaded up ….although it was still peeing good , I wasn't sure the entire engine was getting circulation….

took it home , pulled the lower unit , water pump looks great , pulled the head cover , thermostat isn't stuck , and bypass valve isn't stuck either , shot water up thru the lower tube, it came out the pee hose , then out through the thermostat hole, so all clear there , then poured water back through the head and it came out the bottom , through the vent holes and exhaust so all clear there …..

so now I'm wondering why it got hot and shut down …… maybe its lean ? I'm not sure whats going on …… Its mixed at 50-1 on the oil gas mix as well…….. another question is , do the gas tanks have to be vented ?? I can remember as a kid going out with dad and several times in boats and we would take off and run so far and the boats would shut down , and he would open the gas tank lid vent , and away we would go ….. this tank doesn't have a vent , nor does the new plastic one we just bought … should they ?? any more ideas ??
I also have a fuel filter inline between the tank and primer bulb that is brand new , and I removed the cover off of the fuel pump and the screen is clean..

We need Pappy for additional diagnosis ...

But sounds like your SLOW (Slow speed Limiting Overheat Warning) system triggered, as that intentionally limits the RPMs and mis-times it to the point where you wouldn't want to run her fast.

You also checked everything I would have, which makes me wonder if passages are clear, maybe the impeller is shot and can't pump sufficient flow at higher RPMs. I think I'd replace the impeller, if it were mine ...

I think I'd replace the impeller, if it were mine ...

Click to expand...

I would too. And, Dale is right..... Pappy will know.

as I mentioned in the original post , the water pump looks great , all of it , including the impeller …. I am going to install a new one while its apart , but the new one can't look any better than this one… can the cable adjustments be out of wack and make it have too much ignition timing at low speed causing it to over heat ?? , just a thought , thanks for the help I'm stumped

Check for a wire short on the overtemp sensor circuit. If it shorted out somewhere that could set off the alarm but it would not explain the high temps you experienced.

i checked all the wiring , and unplugged the wire from the over temp sensor on the head when it happened and the buzzer stopped , so I beleve it is working correctly ….. but believe me , the motor got hot ….. the only thing I can come up with was wondering about the timing , cause I know the guy I bought it from had been adjusting on the cables he said .. but didn't know if that would heat it up that fast at a fast idle

I cannot add much because it seems you are doing a great job in your troubleshooting already.
Before you install the new impeller check the housing and make sure that tiny little vent hole is clear......if your pump has it. Think it does.
You will also be able to see if there is any melting of the housing next to the impeller cup.
If the top and bottom of the cup have any grooves that are deep enough that you can catch a fingernail in then the whole assembly needs to be changed.
If the vent hole is plugged the pump cannot get rid of air and will never pump the volume it is capable of. Grooving makes this worse.

I have to idle through a fairly weedy area to get out to good water to test.
While idling the pump will actually "displace" water surrounding the gearcase. This means that it move the water inward and will pull in weeds or whatever you may have there.
You can run on plane through the same area and never suck in a weed because the water that simply travels past the inlets is enough to supply the water pumps needs.
I am working on a 200 right now that has a pump that will not supply enough pressure on the hose and muffs to fill the block but the indicator is working well. I have to use the flush port to cool the engine while I work on this one or it will overheat.

When you idle out from a ramp you can partially block the inlets with an ice bag, weeds or whatever and have enough water to cool the pump and activate the indicator but not enough to cool the powerhead. Follow me?
What I did not read in your initial posting is that you stopped and put it in reverse and added throttle to blow any blockage off the inlets. You stated you went to WOT instead to check it. Can also just shut off the engine which sometimes works as well.
Timing absolutely will not create an overheat. It can and will smoke a piston but the block will be nice and cool and happy while all Hell breaks loose in the cylinder. Lean condition, incorrect spark plugs, etc. will not do it either.

Let's hope the new impeller fixes it. I've seen impellers break free of the brass hub, like "spinning" a prop.

I bought one of the laser temperature gauges. I think I'll make it a practice to establish some expected temp readings for normal operation and bring the gauge along as standard equipment in the future.

Tag. Interesting post.

Good luck OP.


CMOS

Thermostat?

thanks for the suggestions guys, I am waiting on a new complete water pump…. I figure if its apart may as well install a new one.. I don't remember seeing a vent hole in the housing , but there is a hole (1/8" maybe in size) in the side of the supply tube that goes up and feeds the head from the pump …….I thought that was strange but maybe its suppose to be there ?? I checked the intakes several times when we were out and nothing had them blocked …… this lake is pretty weedless , thank god …. the steel plates above and below the impeller have no grooves in them but i am replacing the whole deal anyway ….. i hope after taking the head cover off , checking the bypass and thermostat , and the whole system for blockages , that it turns out to be something silly with the impeller loose on brass sleeve or something , and it will be good to go when we go back out .. I'll let you know …thanks again everyone

no one has addressed the tank vent question …. I have a older metal 6 gal style with the quick turn lid , and a brand new 6 gallon plastic tank with the screw on till it clicks 3 times lid….. can't find a vent on either one ? are they correct ? do they need a vent ? do they vent through the feed line ?

wheelie said:

no one has addressed the tank vent question …

Click to expand...

OLD - Dang it, it's been so long since I've used a metal tank I don't want to comment ... but just read this on-line:

"Those old style metal cans have self-venting caps."

NEW - Per Boat/US

"Tanks Under Pressure - New portable gas tanks may cause headaches for outboard owners.

New EPA-compliant gas tanks don't vent until the internal pressure reaches 5 lbs. per square inch.

New EPA-compliant portable gas tanks and jerry jugs have special fittings that greatly reduce evaporative emissions from gasoline, but they could cause problems for some outboards, BoatUS has learned. New tanks on the market must meet this requirement. Where traditional tanks simply vent to the atmosphere, the new tanks don't vent until the internal pressure reaches five pounds per square inch. A BoatUS member in Florida reported that his tank swelled up like a balloon in the hot sun, and the internal pressure forced gas into the outboard where it spewed inside the cowling, eventually dribbling out.

Fortunately, there are a couple of solutions to this problem. The easiest is to simply disconnect the gas tank from the engine when not in use (open the fill cap to relieve pressure before disconnecting or connecting; otherwise the hose may spew gas) and keep the tank out of the sun. The other solution is to purchase a fuel-demand valve, which allows gas to flow only when the engine calls for it. These are available from gas-tank manufacturers and large retailers such as West Marine for about $25."

But I don't think that directly addresses your question. All I know is, on my ~10-year old plastic tanks with a dedicated vent knob, if I don't open it when running, it'll suck the fuel line/primer bulb flat in minutes ...

The newest tanks will only vent under vacuum, as in when the gas is being drawn from them.
The older metal tanks either had a knurled knob on the fill cap or they had vents that opened via a small pin that is pressed in when the fitting is clipped onto the tank.
I like the older metal tanks as they do not end up looking like a football when the pressure builds in them. Just my preference.

RiverBottomOutdoors - No, it is not a thermostat issue. There is a by-pass system on that engine plus when an OMC thermostat fails it is designed to fail in the open position.

thanks again Dale and Pappy

On my Mercury, the timing (synchronization) is adjusted through arm linkages so I don't think the cable adjustment would cause the timing issue, but you might want to check a manual to see if the previous owner did change something in the linkage somewhere. Are the spark plugs the correct plugs and the gap set correctly?

I'm scratching my head on this one. Only thing I can thing of is when you get the water pump installed is to put the LU in a bucket / barrel and spin it by GENTLY clamping a 1/2 drill on the drive shaft and spinning it clockwise to see if the pump is working well. If you lived near or the motor was run in salt water I'd say that the water passages might be clogged with corrosion . But I don't there is any salt water where yer at. :LOL2:

update , got the new fuel pump installed tonight and put lower unit back on … ran it at idle for about 15 minutes in a big tub of water , no overheat horn and head stayed only slightly warm,,,…. and after the thermostat opened we got warm wear out to he exhaust holes?? down by the anti cavitation plate…….. we'll hopefully get it back out on the lake and try it soon…. thanks any and all who helped or offered possible answers … good people on here …

took her out on the lake tonight….. ran great , ran it for about 45 minutes from 1/2 to full throttle and the head never got over just warm ….. it went 31 mph on the GPS …. no tilt / trim to fine tune it …. 16 1/2 ' Lowe Bas catcher Pro …. fairly heavy boat … so we're happy ….

Well done....you did a great job!