How Hot

[bobwalter]

I have an '83 Mercury 200 hp. Serial #6489792. It has sat in a field unused for at least 10 years. The carbs have been rebuilt and a new water pump and impeller installed. After chasing bad wires on stator, trigger, switchboxes, and coils she seems to run good. I have it in a tank and when cold at idle runs with 15# of water pressure and a solid strong 10' long stream out of the pee hole. As it warms up the pressure begins to decline. As it gets hotter, the stream gets less and the pressure goes to around 5#. The stream begins to look turbulent and becomes very hot. After about 7 to 10 minutes the water in the stream is too hot to touch and looks to be steaming. I think this is too hot. I don't have a temp gauge but I can touch the cylinders for several seconds without getting burned. How hot should this thing pee? I will put a thermometer in it tomorrow if I can find it. I need some opinions. I would like to launch late next week if possible.

Whatcha think?

Bob

 

[redjmp]

Re: How Hot

I think you may have a blown head gasket/warped head possibly from an over heat. Hot gas is blowing by and into your cooling manifold and its driving the coolant level down so the top of the block gets no coolant so as to become hot enough to create steam.

 

[bobwalter]

Re: How Hot

Compression is 120 all the way across.

Bob

 

[redjmp]

Re: How Hot

You need to do a leak down test i think and then do one when its steaming. Or it may be a crack in the block.

 

[tashasdaddy]

Re: How Hot

very possible.

 

[emckelvy]

Re: How Hot

How warm is the exhaust manifold cover? If it's getting any more than lukewarm there's certainly a problem. Have you checked/replaced thermostats/poppet valves?

 

[bobwalter]

Re: How Hot

I have not touched the thermostats or the poppit. I will replace them today. If the thermostats weren't opening, wouldn't that cause it to not pee? It begins peeing within 10 seconds of starting with a very strong stream and about 15# of pressure.

Bob

 

[Texasmark]

Re: How Hot

I guess an 83 200 is a V6 which has 2 banks of cylinders. On the son's '95 150 there is a stat at the top of each head with a 143F (stamped on the pellet) stat in each head under a cover with 2 bolts holding it on and a hose barb screwed into the back of each. Hoses are connected to the hose barbs, tied together and one tube goes below the powerhead to dump the water. Originally the pee tube was tied in this line which meant that you got no pee till the stat(s) opened. We moved it to the other line...see below.

The main engine water outlet is in the center top of the engine block behind the flywheel. It is not in the stat circuit so the water from here is usually just warm if the engine has been running for awhile.

A hose from it originally went below and dumped below the powerhead. We moved the pee line to this tube (cut it and installed the tee from the other tube) which allows pee as soon as the powerhead fills with water.

140F is the temp most hot water heaters are set to for the Normal position. That'll give you an idea what 143 feels like, but that is the opening temp.

If the stat starts to open at 143 it's going to be over 150 by the time it gets fully opened. You aren't going to hold your finger on that head for more than a couple of seconds and depending on temp and humidity, the outlet could be steaming, or appear to be.

I also noticed that the starboard bank is slightly higher than the port bank (the way V engines are made) meaning that there has to be enough water pressure available so that when the port stat opens, there is still water filling the passages around the starboard stat. Otherwise it won't be full and the top piston of the starboard bank could overheat. If you pull both stats and start the engine on muffs you'll see what I mean....but only do it at low rpm's and long enough to see that the passages are clear. You can stick your finger over the port hole and watch the starboard side continue to fill and run out that hole.

HTH,

Mark

 

[bobwalter]

Re: How Hot

Ok guys.
Here is where I am at. I assumed that if it peed the stats were good. Well I bought new ones and when I opened it up, Surprise. There was virtually no thermostat left. The port side had the top of the stat left in the gasket. The rest was gone. The stbd side has some residue left in the gasket and nothing more. I opened both sides and left them open while I ran the engine for a few moments. Water flowed well from both sides and hopefully flushed anything inside out. I installed the stats and ran about 3 gallons of fuel through it while in a tank at around 1200 rpm and it seems to be holding the proper temp. It did not want to pee with the new stats, but I cleaned out the pee hose and it peed fine. Must have knocked some residue loose.
Final question (I hope). Just below the powerhead in the shroud that runs to the lower unit are two rectangular holes facing the rear. Is exhaust (smoke) and some water spray supposed to exit those holes while running? If so, good. If not, what caused this?
I appreciate the help you have given so far. You are so right about getting a FACTORY service manual. I have consulted it daily and it has helped me understand how things work. I also bought the parts manual and it gives good breakdowns of everything. You guys do a great service to those of us with less experience.

THANK YOU,

Bob

 

[Turkey]

Re: How Hot

A question, I'm new to outboards but know cars pretty good, but wouldn't the stats resrtict water flow to the pee stream while the engine was reaching normal operating temp (NOT)? And as they cycled through the water temp range intemittantly restrict water flow as it worked to maintain NOT? Just curious because it is probably an issue I'll encounter sooner or later and would like to know what to watch for.

If you have seen any of my threads you will know I have the boat parked do to running way too many rpms and thus creating higher than is good operating temps.

 

[Texasmark]

Re: How Hot

The holes you are referring to are exhaust relief to allow easy starting/idling of the engine. You usually get exhaust gas but may or may not get a little water vapor/spray. Presence or absence of water there is of no concern to you.

Back in the 50's when an engine idled, it bubbled up from the exhaust tube. Somebody saw that and figured that the engines would start/idle better with no back pressure so they fixed the problem. Then everyone had it.

Turkey, your question isn't clear but if I understand you correctly, not all pee tubes are connected to the outlet(s) of the stat(s). In a lot of engines the pee is taken off the exhaust manifold which has water (to cool the exhaust passages) as long as the engine is running regardless of the temp. Problem with monitoring the stat output is that you have to wait till the stat opens to know if your pump is working.....that could be awhile.

Mark