Operating Temp on a Bigger Motor...

[HighTrim]

Hey Guys,

The previous owner of my Johnson told me he was overheating a ``bit``, lol, I think he was understating the problem. I changed the impeller today, and noticed that the rubber grommet on top of the impeller housing where the water tube slides in was shoved in the hole of the impeller housing, definately blocking any water from exiting. Figured problem solved....When I fired her up, seemed to cough quite a bit, ran her on the muffs at idle, just under 1000, for about 5 to 10 mins and noticed on the temp gauge she got quite hot, around 160 degrees, which is just under redline, so i shut her down, no warning horns or anything. Ive never had a motor this large, will running one on the muffs at idle create that kind of heat? I know that my t stats are suppose to open at 145, and as the engine speed increases water pump pressure opens the relief valves, allowing the engine to run cooler at higher speeds, so am i heating up since im not opening her up on the water and am on muffs? Faulty pressure valve or t stat? Does anyone use a Markal Thermomelt Stik on the cylinder heads to gauge overheating, apparently if a 163 degree stick melts on my head my engine is running too hot. ANy input by you pros would be great, dont want to take her on the water overheating , tks

ALso I assume I should re torque all my head bolts if it was running hot, 18-20 ft lbs.?Should my warning bell go off if i ground my heat sensor?

I also replaced the plugs with NGK BUZ8H, are these ok for this motor, could they be causing the coughing?

 

[HighTrim]

Re: Operating Temp on a Bigger Motor...

No ideas at all?

 

[mokaction]

Re: Operating Temp on a Bigger Motor...

Put a post at http://www.marineengines.com for JOe Reeves, he is the man 4 Johnson motors. Also did you do a compression check? Could have scuff cyclinders?

Larry

 

[HighTrim]

Re: Operating Temp on a Bigger Motor...

Yeah compression was fine, 105 across all 6 cylinders

Also that site is under construction

 

[Silvertip]

Re: Operating Temp on a Bigger Motor...

Since you have good water pressure and still run on the hot side, pull the thermostats and check them or simply replace them. They control engine temp at idle. Once rev'ed up the poppet valve opens to admit cooling water. If you can't hold your fingers on the head for more than a few seconds, it is probably running too hot. As for the plugs, although Champions are recommended, the NGK's should not make the engine overheat at idle even if they are a couple heat ranges wrong. You can short the temp sensor wire to ground to test the system. The horn should sound. Note however, that this test proves the horn system is functional. It does not mean the sensor itself is activating at the proper temp.

 

[jurgenscraft]

Re: Operating Temp on a Bigger Motor...

The very first thing I would check is the thermostat, make sure the thermostat is opening as required in the manual, secondly using muffs for any thing other than flushing is not a good idea as muffs cannot supply enough water into the cooling system do as to ensure proper cooling especially with larger motors, rather take a 45 gallon drum lay it on its side and cut a opening large enough for the gearbox and water inlet openings and water pump to be covered by the water in the drum.I have this sort of a arrangement made up for my 225 Evenrude and it works well for flushing as well as short duration testing.Or if you test a lot have a sheet metal shop make you up a tank.
Have you tested the motor under working conditions, on the lake or river,?have you flushed the motor out with a flushing product,?
you mention a temperature gauge, is it in good working order,?( wiring etc.)
try these basic tests and see what happens.
Reghards William Wright.

 

[HighTrim]

Re: Operating Temp on a Bigger Motor...

Ty both for your replies. I only use the muffs for short testing, under couple minutes usually, since i want to get everything right before bringing her to the water, so no, i havent had it in a lake as of yet. Silvertip, would the NGKs cause the coughing? They were very expensive plugs and will take them back if you feel the champions would be superb. I felt the t stats were the problem, just dont know of any such tests other than taking them out and putting them in boiling water with a thermometer to see when they open. As far as the gauge , im assuming its working, although it does jump sporatically as it increases, not smooth like im use to, any ideas on this?

 

[HighTrim]

Re: Operating Temp on a Bigger Motor...

Also my manual states to torque the flywheel to 140-145 ft/lbs, this seems high for such an older motor to me, should this be lessened due to its age, or is it still safe to torque it to such a high amount.

 

[Silvertip]

Re: Operating Temp on a Bigger Motor...

I just responded to a similar post (rough idle) although no mention of sneezing but never-the-less here's my response to him.

The service manual has a note that warns as follows:

After a period of time, the idle chamber cover gasket can be sucked down into the L-shaped passage in the carburetor body, restricting idle fuel flow. To prevent this from occurring, carfeully cut out a L-shaped portion of the gasket corresponding to the idle passage in the body.

Obviously all of the carbs would need to be disassembled to remove the idle chamber cover. You cut the L-shape into the gasket and button things back up. That would obviously be a good time to rebuild the carbs but if they were already done, you should be able to just cut the slot and reassemble.

As for the plugs, I really doubt they are the cause of the trouble. There is much written on this forum regarding Champion vs other plugs in Johnny/Rude engines but the only real issue is the closeness of the heat range between the two plugs. A given heat range on the Champions (hence what the engine was designed around) may not be precisely the same heat range on the NGK. The difference however would be slight and I would not rush to the conclusion that the plugs are the issue.

 

[HighTrim]

Re: Operating Temp on a Bigger Motor...

Ty silvertip for you assistance. I will try that tomorrow and reclean the carbs while im at it. Im also going to try testing the Power Pack with an ohmeter to see is there is a defective diode. Is my temp gauge suppose to jump sporatically like that, Ive never seen one like that, and if not , do you know of a test for this type of gauge, ive never had to repair one myself. I also just ripped out the t stats and gonna pick up a couple new ones tomorrow.retorqued all the bolts and screws, although one busted one me, lol, and also noticed one of my spark plug wires was severely corroded inside the boot, I feel this is likely my problem, so will order a new coil and wire package. Tks again

 

[Solittle]

Re: Operating Temp on a Bigger Motor...

If you plan on doing your own work a temp gun is a must. It will not only tell you the temp but since the reading is where you point it it can aid in identifying where hot/cool spots are.

 

[HighTrim]

Re: Operating Temp on a Bigger Motor...

So the Markal Thermomelt Stiks wouldnt give me an accurate reading? I just pulled the covers for the t stats and found cob webs in one....would this lead you to believe waters not getting up that far or would the cover side of the t stat housing stay dry anyways?

 

[Silvertip]

Re: Operating Temp on a Bigger Motor...

Temp sticks are fine if you have access to them.

 

[HighTrim]

Re: Operating Temp on a Bigger Motor...

Ok tks guys, I guess my final questions are is it safe to torque the flywheel nut to 145 ft lbs like the manual states even though it is older, will the 31 year old bolt stand up to that kind of torque. The ends of my spark plug wires are corroded where the coil in the boot meets with the wire in the jacket. Can I cut the wire back and re soder them together as long as I have enough room or do i need to buy complete new coil kits. And finally is there a test for the temp gauge to see if it is operating correctly, it jumps sporatically as it is increasing, not very smooth. Thks for all the help.

 

[HighTrim]

Re: Operating Temp on a Bigger Motor...

Tried cleaning the ground on gauge, still seems to jump, guess its just an older gauge and is reading fine, just not as smooth as when new.

 

[HighTrim]

Re: Operating Temp on a Bigger Motor...

Bumping up for fresh eyes...