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Overheating problems

butty99

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Hi a newbie here so be gentle!! I've got a 96 yam v4 115hp outboard that's overheating when hits 4000 rpm. It started when I didn't start it for 2 months and went out on it increased the revs and the alarm when off and the red thermometer sign came on? When it's cooled down you cruise all day on it along as it doesn't go to 4000 rpm? What I've done so far is inspected my water pump (perfect) , changed the tstats ( old ones where good aswell) ,ran saltaway thru the engine numerous times, checked water intakes (perfect). Had a check about with the temp sensors while running to see which side was setting it off seemed the left side !! Bought a heat temp gun and had it on idle and checked all over the cylinder head for temps and funny enough came up on right side hitting 55 c just above the spark plug , that was the hottest spot with the rest averaging 45 c ? So I was wondering a few things reading about putting rydlyme thru it ? Anyone done this? Anyone know how to properly check the temp sensors to see if they are definitely working? Prv where is it, how to check it?
Is it a simple as cleaning the cylinder heads ( 20 yr old motor thou)
Can anyone point me in the right direction please thanks
 
I have a 1994 Pro-V 115hp and am new to Yamaha but very familiar with the 1990 115 hp Johnson cooling system. Here's what you've done and my comments:

1) Inspected my water pump, perfect.
(how did you inspect it? Did you look at the impeller?

5) Bought a heat temp gun and had it on idle and checked all over the cylinder head for temps and funny enough came up on right side hitting 55 c (131F) just above the spark plug , that was the hottest spot with the rest averaging 45c (113F) ?
(those temperatures are quite cold, once the engine warms up it should be around 60c (140F) that is what the thermostats are for. You should check the temperature after the engine has run in the real world and see what you get. Try to get the alarm to go off near a shallow area that you can then jump off the boat and use the heat gun)

6) So I was wondering a few things reading about putting rydlyme thru it ? Anyone done this?
(there's other products one can use, I've used on an old diesel tractor what Mercedes Benz uses, Citric acid, but on an outboard I don't think those things work well because the water is getting spit out the engine. and if you put it in a tank the whole outboard is exposed to the acid. The procedure for the diesel tractor engine calls for first filling the cooling system with dishwasher detergent water mix (it does not foam up) and running it 20 minutes after it is warmed up, then draining and testing for no oil in passages. It is a long process even in the closed water cooling system, forget about it for an outboard)

7)Anyone know how to properly check the temp sensors to see if they are definitely working? Prv where is it, how to check it?
(Do the water test described above before you test the sensors. You can isolate the temps if you are right next to the sensor with the gun. By the way, the further the red dot is from the gun the less precise the location is. I put the gun as close to the dot as I can. My gun ETC8380 says it is 3/4" from pinpoint at 9" away, and 3.15" from pinpoint at 38" away. I put that red dot like one inch away from the gun if I can. I've never removed the Yamaha sensors, on my Johnson they only came out if the cyl head cap was removed, I'm sure Yamaha improved on that. The way I would test the sensor would be to put it against a heated metel plate that your gun says is whatever temp is supposed to set off the alarm. )

8) Is it a simple as cleaning the cylinder heads.
(I've done it on my 1990 115 Johnson (and other Johnsons) and it looks like the same job on my 1994 Yamaha 115, likely simpler, as Yamaha looks like it copied the Johnson and improved on service hassles (to change the t-stats on a 1990 Johnson 115 one has to remove the entire powerhead, 6 hours labor!), it looks like the head removal job is at worst the same and likely much easier than on the Johnson. On the Johnson 115 you remove the heads and scrape the corrosion off with screw drivers, picks, whatever fits. I take them off and have my 11 year old clean them up, then I give it a few finishing touches, and put everything back together. The diagram for my Yami 115 shows zinc anodes in the heads)

P.S.- I'm almost at the point of water testing my engine, and will go thoroughly through it with the heat gun before water testing in the real world. That heat gun can save you a lot of unnecessary work.
 
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With your V-4, you likely have two overheat Sensors, my 3-Cyl has one, up by Thermostat and an arm under one Thermostat Cover Bolt to keep it in, easy to remove and yellow and black leads to disconnect.

With an OHM Meter and a Candy Thermometer in a pan on stove, you can confirm continuity happening above 188f and circuit opens again as it cools below 150f. Check your SM for your temp specs. With all that ocean/lake water to draw from, it's not uncommon for most of engine to feel normal on an overheat condition. Never ignore an overtemp based on how it feels, check the sensor and they're usually correct.

I've done all you have plus and after a few minutes close to 4000RPM (Manatee's 25 MPH Speed Limits) Overtemp sets off. First warning cools quickly and head does not feel hot, second warning does not cool quickly and heat can be felt on head. Just finished three :45 minute plus Salt Away rinses with 20 gallons water with two gallons of Salt Away (heats up the water barrel very hot) and it had no effect on condition. Tomorrow's plan is to do compression check and then pull the head and exhaust plate to look for blockage or voids. Put new head on fifteen years ago due to same symptoms from a pinhole corrosion leak into one Combustion Chamber, head still looks new under head cover, fear it my be my cylinder block's turn now.

Can run at low speed without overtemp, but higher power settings with a pinhole leak from combustion to water jacket can blow dry a small area in water jacket and cause great damage.
Art
 
Just a note on cleaning solutions inside aluminum motors.

Salt Away is a proprietary (secret) formula, but it's basically acid. Some use vinegar (think Walmart sells a 'cleaning' strength version) also acidic and of course the citric acid mentioned.

Acid won't hurt aluminum, they store acid in aluminum containers, not so with alkaline solutions, they will eat the bottom out of your aluminum bucket overnight. So use caution with dishwasher detergents (think they're base, not acidic) and check what's in Ridalyme before allowing prolonged contact with your aluminum. Their literature says it will dissolve zincs.

A good thorough rinse following an alkaline type wash might be enough, but I wouldn't allow prolonged contact.
Art
 
My 90TLR overheat issue was similar to many described here, occurring only after 'on-plane' operation for 5 to 15 minutes.

In addition to Oil Injection test, Fuel Lines, Filters, Carbs, Fuel Pump, Water Pump and Thermostat, PRV tests, I had pulled the Head Cover to find no visible corrosion, but an offwhite paste buildup at bottom (exit, I think).

I then did extensive barrel runs with two gallons Salt Away along with twenty gallons of City Water in a 33 gallon plastic trash container. I had to slow idle RPM below 700 after brief runs at higher RPM caused so much suds that I was losing Salt Away, reminded me of Joy in your Dishwasher:eek:.

I did four longer runs :)30 to an hour), heating the barrel (and engine) hotter than you could place your hand into, final run went up to the 188f Buzzer.

Water run at 25 Knots showed no improvement at all.

Then pulled the head and saw clean water jackets around cylinders but a pile of crumbled *oxide* built up in the two lower, larger passageways (exits I think, cooling flow chart is not in any Manual I have or found online). A quick dig with small screwdriver pulled a 1/4 to 1/3 cup into a paper towel and I'm now sure (again) that this blockage will have been the cause of the issue.

I poured straight white vinegar in the cup and it got a little cloudy but did not seem to dissolve the *crud*, will report if 'Finish' DWD or Clorox TBC has any effect but don't think I would allow that stuff in my engine. Expect Salt Away will be great to prevent corrosion (see OH DOT report) and keep an engine clean, but my condition required disassemble to remove (dig out).

I will clean more thoroughly with cylinder brushes and a pressure washer and will also try and remove the Exhaust Cover to clean in there as well.

Expect a week to ten days for gaskets/bolts delivery, but I will post back (New Thread) on results:cool:
Art
 
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