Synthetic 2 Stroke Oils - Current Minor Engine Issue

Smashdn, what's model# an serial# of motor?
I'll look in books tomorrow. Now not saying this is the your problem, but had a Nissan this yr. with weeds-grass sucked up , it settled in bottom of head, it peed good out tale-tell, because tale-tell was above theweed-grass blockage in head. If he idled long , heat alarm. Wot he was good. Also seen this yr. a c40 with issues like this, motor was run in same body of water, calcium or iron , or being boat was docked with electric flow , from 110 electricity to dock don't know . but block water passages were half way clogged.

I am pretty sure it is an 60F. 99/00 2 stroke 60 horse with oil injection. (might be a C60, I will have to get a picture tonight of the serial tag. Okay, not mine but it is one of these > Yamaha 60 2 stroke Madras - YouTube or this 2001 Yamaha 60hp 2 Stroke Outboard Motor - YouTube)

I tore the head apart last night and took off the exhaust side water jacket to see if there was anything stuck in there. All was clear. Had a little fine silt built up on stuff but all holes and ports were fully open.

I ran it at the creek last night and it ran really well at first. Started quick, idled off the trailer, idled fine with no buzzer, strong stream from the tell tale. I opened it up and ran a few hundred yards on plane down and back. Pulled back into the bank and let it idle again just sitting there. Took about 15 minutes and the overheat alarm went off. Popped the cowl off and pulled the pink wire from the temp sensor. Buzzer stopped. I think I just isolated it and identified that it is indeed the overheat sensor and not the fuel level sensor. I pulled the fuel level sensor why and the buzzer continued.

So I definitely have an overheat condition. Why is the big mystery. Water is definitely getting into the water jacket, it was wet when I pulled the head. The very top cylinder was not wet though? Either it dried out in the time it I pulled it or it wasn't getting water up there. Still nothing that would visually indicate a blockage. The top cylinder walls looked no different than the bottom two. No scoring or discoloration that would indicate it is not getting oil.

I am going to pull the lower unit off tonight and look at the water pump again.

a couple of us have used pennsoil synthetic from wall mart for years and no problems, price is good

I am thinking I may do a rubbermaid trashcan and some water and maybe a descale through it.

Ran it in the garbage can for probably an hour. First 45 minutes if was in about 25 gal of water and one gal of muriatic acid. A little bit of the dried silt film came out as i could see liitle bits of it in the water after i turned off the motor. Rinsed it in clean water with just a touch of dishsoap for another 15 minutes.

Temp gun read 137 at thermostat housing. Around 155 on the outer cylinder water jacket.

No alarms. I'm just going to send it.

Took to lake. Not fixed. I'm at my wits' end. Only started alarming after trimming up and idling over a submerged beaver dam. After that it didn't matter if it was trimmed up or down. If i idled for more than a little the alarm went off.

I got to looking round the innerwebs the other day and really looked close at the parts diagrams for my outboard. I noticed that there is supposedly a rubber grommet or seal at the base of the water tube. I went ahead and dropped the lower unit to inspect the impeller and water pump housing again and noticed I am missing these parts. So I called up the boat part place and got them on order. Fingers crossed that makes a difference.

In a related knucklehead move made in frustration and haste over the cooling issue, I went ahead and was going to use my boat to hunt out of the other day. I was second at the ramp and the first guys were nowhere to be seen so I was all alone. Backed in no problem. Motor started right up. I hop in to back it off and it wouldn't shift into gear. Pull it out and take a look. I misaligned the splined shift shaft with the receptacle on the upper leg of the engine. Luckily I have tools to fix, or so I thought. Sockets and ratchet check. I get the four bolts off but now need an extension to get the bolt holding the trim tab/anode off. No extension. Stuck on the ramp. Luckily the guys I was hunting with showed up with their boat and we ripped anything of value off of my boat and locked it in the truck. I piled in with them and went hunting. Got home and had wife help me get LU dropped and back on, lined up properly this time.

Attachment 390288

You definitely need those seals for the water pump. Surprised you were even getting water to the powerhead with those missing.

Put a temp gauge under or in the dash, replace the plug in the cooling jacket with a sending unit that is a match for the gauge, and get to the facts. I did this on my 115 Mercury 2 stroke and discovered the 120 thermostat was stuck wide open, and I believe it has been that way for a long time. Got a new kit including seals and poppet to install when I get to it.
As for oil, syn 2 stroke oil is I believe over kill. TCW3 is a must, IMHO, and for me after years of running Quicksilver, I now run Penzoil 2 stroke TCW3 for $17 a gallon delivered to my door.
All my 4 stroke motors run syn oils and I believe in it 100% - but not for 2 strokes as per it's diluted end result.
As for the water flush, I have used a gallon of simple green in the trash can of water and ran the motor in it for a while, but with that I was not impressed. Perhaps it has something to do with water quality of where one usually runs their boat, who knows.
BTW - be sure to silver anti seize everything near the thermostat when you reinstall, and if you do it good like I do, some will probably get on your nose too!

All grommets and seals installed. Came off plane and idled into cove alarm goes off.

Not sure now.