75' Mercury 110 leg getting hot enough to steam

[Mabe]

Bought a boat with an old 9.8 hp Merc 110 a few days back. Spent the weekend cleaning it up, getting everything running as right as I could. Water is coming out the P-hole now like a champ, and the upper unit seems to be cooling a-ok, but I noticed after I took it out for its test run that the Leg above the lower unit was hot enough to steam water. Wondering if this is normal for this engine? Blocked exhaust? Would really appreciate help from anyone more familiar with this outboard. Thanks in advance!

 

[Scott Danforth]

that is the exhaust passage. water should be mixing with the exhaust. should be really warm to the touch, however not hot enough to steam.

 

[Mabe]

Got ya. I'll spend some time with it on the stand, see if I can find anything gumming up the works. Not sure what the previous owner did to this thing, but the P-hole was melted shut on the exterior and I had to bore an almost concrete like substance out of the hose and spigot where it empties. That is to say I wouldn't be surprised if the exhaust is fouled up too. Thanks for the prompt reply!

 

[GA_Boater]

Welcome to iboats.

Has the impeller/water pump had any service lately? Doesn't sound like it. One of the first places to start when she runs hot.

 

[Mabe]

Replaced the impeller when I took her apart to clean and grease, local boat shop had one in stock when I went in to buy oil for the lower unit so I figured might as well. Old one had a good sized crack, but no missing fins. Put it all back together, ran it in the barrel after getting the proof hole opened and its shooting a steady stream, no sputtering or steam there so I figured the pump itself was good. Water coming out the proof hole is warm, but not hot. Had it going in the barrel for 10 minutes or so to see if the engine itself was having any issues at idle, and didn't notice the leg become hot at that point. Was only after 30+ minutes on the the lake doing everything from idle to WOT that I went to take it out and noticed that water was steaming on the leg. That was why I was curious as to whether this was normal, while it was submerged still in the water I assume it would be much cooler, but I don't want any heat build up inside reaching a point where seals and what have you start to break down.

 

[Mabe]

Follow up question after a bit more observation in the barrel, even at idle all exhaust is exiting down by the prop, no flow at all from what I assume is the idle exhaust port on the rear. Is this an issue and if so what could be causing it? Still pumping water fine from what I can tell and no overheating up top, can hold a finger next to the plugs forever.

 

[Texasmark]

On the 9.9 a thermostat is optional. If you have one the opening temp is around 125F. That's a high warm. If no stat, in the water, running at a reasonable speed, the back of the block should be mid warm. The tell tale usually comes from the exhaust manifold which requires water continuously while the engine is running to prevent it from overheating....Stat or no stat, separate circuit.....follow the hose. Exhaust manifold is on the left (Port) side looking forward.

In a barrel, the exhaust warms the water if you don't splash it out and have to keep the hose running in the tank so the engine will run hotter.

 

[Mabe]

Thought I'd give an update, the idle exhaust port was completely gummed up inside, cleaned it up and it's porting exhaust out at idle/low rpm fine now. Leg is still running hot at times, but not having cooling issues at all with the engine, so it's moving water fine. I'm going to call this one good for now unless the leg starts getting hot enough to warp the paint. Thanks for all the advice guys, I'm sure I'll be back for something in the future.

 

[Texasmark]

Why don't you do a "decarb" and run some Sea Foam in your tank in addition to your mix for awhile....directions on can for normal usage. Decarb is in the archives or an easier access it google search engine. Just type in the word. It may get it out.....probably oil and water from a lot of low speed operation in a cold climate....water and oil can make a gooey jell, if enough of it and for long enough.