Outboard Overheating?

[FairfaxFisher]

I purchased a 2005 Tracker PT175 a couple weeks ago with what I believe is a 2003 50HP Mercury outboard. Everything has been serviced and the motor starts 1st-2nd crank. The motor runs slightly rough at idle, I haven't adjusted it at all because the tachometer doesn't work. Regardless, the motor shoots good water, leading me to believe it's not the water pump and/or impeller. Where the concern comes in for me is that when hooked up to my garden hose muffs, the water being ejected is for the most part cold, with moments of hot water coming out. (hot meaning not scalding but still uncomfortable), while the side of the engine block remains warm/hot after a couple of minutes of idling. (I can put my hand on the block for however long I need without feeling any intense burn) My question is why would cold water be pumped out if the block is hot, and why would it not be consistent temp? Is some water not reaching the cylinders to cool them? The last thing is when the motor is turned off or it sputters out, warm water starts coming out instead of cold water for the last few seconds, until the last of it has drained. Looking any input helpful, hoping its something I'm overthinking and not a serious issue, the boat doesn't have a temp gauge.

 

[Faztbullet]

Because its a water pump indicator..only shows water pump is working, not a test of cooling system.

 

[racerone]

^^^---Applause on the above information.----Have seen many motors with tell tales destroyed from overheating.

 

[FairfaxFisher]

Because its a water pump indicator..only shows water pump is working, not a test of cooling system.

Okay, so how do I know if it's overheating then? I haven't noticed a decrease in power, then again I haven't really had it above idle speeds because it's in my driveway. Should I get a laser temperature scanner?

 

[FairfaxFisher]

My water pump is working well, steady stream being ejected. Water is inconsistent, mostly cold while the side of the engine block is warm after a few minutes at idle, sometimes the water is warm but there is no pattern it seems. When the engine is shut off, the remaining water being drained out is warm almost hot. 2002 50HP Merc. Any input appreciated.

 

[Texasmark]

Follow the tube back to the origin. Where is it connected? I ask the question as you have the exhaust loop and the powerhead loop controlled by a thermostat and possibly a higher rpm popoff valve...not up on your engine. The Tstat will make the water in the block hotter if tapped off there whereby at idle, if tapped off the water jacket cover over the exhaust manifold, it may not get all that hot.

In either case flow is a function of rpm (obviously) and on some engines pee is taken off after the Tstat meaning the stat has to open for any water to flow and shuts off every time the Tstat shuts off....my kids 150 was plumbed like that. My 90 and 115 were plumbed off the exhaust manifold water jacket on the Port side of the engine and if the crankshaft was turning there is/was pee.

 

[GilLesS72]

Okay, so how do I know if it's overheating then? I haven't noticed a decrease in power, then again I haven't really had it above idle speeds because it's in my driveway. Should I get a laser temperature scanner?

Yes get a laser. Then look in the manual for reg temps at idle.
The block will feel warm to the touch (as it needs to be). Better with the laser but an old trick is to put your bare hand on the side of the block, you should be able to leave it there for three seconds before it starts to get uncomfortably hot. Take note that if your bloc needs to be warm on idle, USUALY the thermostat doesn't nees to open to cool it down at idle. If it does open after idling for 15mins on muffs you have a problem that needs to be addressed.