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We did our maiden voyage yesterday in our new to us 1988 18 Outrage. The engine starts immediately but I think I'm hearing an innitial back fire. At arround 1000 rpm it temp gauge is reading over half and the telltale has a strong stream. On plane the temp rises to over 3/4 and the stream is weaker. I changed the impellor and repaced hoses before and am planning to new thermostats.

any thoughts would be appreciated.

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This is just my two cents. I'm thinking the thermostat is closed, with most of the cooling water bypassing the cylinders until the engine warms up, then as the thermostat opens up, most of the water is going through the cooling passages around the cylinders. You are in Florida so I'm thinking there may also be a salt/corrosion problem in your engine. It may help to pump some "Saltaway" into the engine and let it sit and do its thing. I'm probably wrong but that can't hurt. Probably the thermostats though. When you put your hand into the telltail stream is it warm or hot? I think it should be just very slightly warm.

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If you change the water pump you should also change the thermostat and poppet valve. The latter is probably your problem, though I find that these 2.0 liter motor typically run VERY hot at 1000-2000 RPM before the poppet vale opens, and when you have a sticky valve, you need to open the throttle up above 4000 RPM before the poppet valve will open and then you can back off on the throttle to cruise at slower speeds and the engine temperature will stay low.

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Picking up the thermostats today and trying it tonight. Also may run it off premixed fuel to see if there's a difference. The boat came from the upper Chesapeak Bay so it hasn't seen much salt water, until yesterday. It has been sitting a long time though. thanks,

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I just put new thermostats in. I didn't have much time but ran it long enough to warm it up. At 1800 rpm it climbed to about 5/8 on the gauge. The tailtell water is steaming. I may try running it on premixed fuel out of a can to see if there's a difference. Maybe it's not getting oil?

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If your warning horn is functional you should get a Beep Beep Beep when you turn the key switch to on. If that works you should be getting oil or you would be getting an alarm. Also if the motor is running hot you should get alarm. Steady tone for oil beeping for temperature.

That is not to say your motor is not running warm. Do you know the temp of the thermostats you installed i think those motors run just around 200 deg. don’t they?

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I've had the same experience with an '87 135 Black Max on my 18'. Temp guage at idle and low speeds indicates thermostat set points (new themostats which are 164 if memory serves) Once I'm rolling at anything over 4000 RPMs temp climbs to 3/4 or even 7/8 on the temp guage.

What I've learned is, there are 2 factory temp probes of different lengths which seem to indicate different values at higher engine speeds. A good guess would be, the short one incidates water temp/ cylinder head temp and the longer one indicates conductive block temp. I know that those with the short probe will experience a temp drop once the poppet opens.. I don't. However, all indicators tell me that water flow and operating temps regardless of indications is a constant. I've replaced my thermostats every other season, checked the poppet and trimmed a spring coil for earlier opening, and I've replaced the water pump every other season opposite of the thermostats. When I run at high load, the exhaust has a good water flow and I can rest my hand on either cylinder head.

I've been running this way for years. The temp alarm never sounds. There are no problems. The 2.0 V6 Merc is the best outboard I've ever owned. Oil injection still working. I've replaced a few stators which seems to be the weak point. If you replace yours, get the red one which is Mercury's improved version.


Chris

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That is exactly when the poppet valve should open up and your engine temperature should drop back down to under 1/2.

I'll say it again: replace your poppet valves when replacing the water pump and thermostats.

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I've done the poppet valve, impellor and lastly the thermostats. I got an email from the previous owner saying it always ran hot. It's in the shop right now. They're recomending a water pressure gauge. Anyone agree with that?

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No, that makes no sense. A water pressure gauge will only tell you if you have low water pressure, it does not solve the problem of low water pressure.

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That's what I thought.

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Got it back last night. The shop ran it for about 45 minutes on plane and used a laser thermometer on different parts of the engine. Most of it read 140-170 degrees with one hot spot at 190 and the alarm works but never sounded. So there could be an obstruction somewhere that’s limiting flow. They’re hesitant about tearing into it because of it’s age for the fear of breaking off bolts and suggest just using it and keep an eye on the temp.

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Good. I was going to suggest an infrared thermometer (the laser part is only a pointer) to actually see what's going on.

I agree. Use it, enjoy it.

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This is off topic, Tom, but speaking of an infrared thermometer, you can pick one up at Harbor Freight for around twenty bucks and its a good thing to carry and point at your wheel bearings or the heads on the engine once in a while. It could save someone a lot of heartache and money.

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Our "second maiden voyage" will be to the antique boat show this weekend. Putting in on Lake Eustis, putting throuth the Dora Canal to Lake Dora and hopefully find somewhere to tie up to walk the show. Weather's looking perfect! Thanks againf or the help.

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Do you know if the engine was previously used in salt water? If so, might be worth running some Salt-Away through the engine while idling on the hose...

http://www.saltawayproducts.com/Produ...oducts.htm

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It's been in mostly fresh to brackish water until now but I do have a bottle of salt away I may try. I ran it on a hose last night and the tell-tale seems more consistant, so maybe it's slowly cleaning itstelf out.

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Unless the boat spent it's entire life on the Susquehanna, it has been in brackish water as soon as it went out in the bay and turned south. Salt-a-way and let it sit, do a run for 5 minutes, until you can tell it's all the way through the system then tun off the water and wait. Give it about 30 minutes to an hour and repeat a couple times. it will clear out the old deposits.

I suspect the previous owner was worse than i am about flushing his engine, i flush mine 3 or 4 times a year and i boat in the lower Potomac and out on the bay. I had to do the same with my old merc that came from NJ, I think the previous owner only flushed it in the fall when he pulled the boat.

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We took the boat to the antique boat show on Lake Dora saturday. Short trip of mostly putting but some running. During the last run I throttled up to over 4000 rpm and the alarm sounded. The telltale is much stronger and more consistant than before, but still steaming.

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Just a quick update. Running out of serviceable areas on the cooling system I started going back to see if I'm missing anything. My generic shop manual doesn't cover any of this but I found an exploded view of the poppet assembly and water pump on line. Turns out the poppet valve was missing the stainless washer that back the diaphram. Without it the spring pulls the diaphram partially into a water passage. A $3 part later and it's running great with the temp gauge reading from just over 1/2 to 5/8. Now I can focus on the boat. thanks.

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I have one of these engines also, and in reading through this discussion everything pointed to the poppet valve. Glad you got it repaired.

The other thing to look out for is a defective temperature sender on the engine, which can give you wrong readings on the gauge. I have had this happen on two different engines.

Typically with Merc V-6's, they need to be warm to idle properly, hence the poppet valve which restricts water flow below 1800 RPM. As the boat planes off and the valve opens up for full water flow, the temp will drop considerably.