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Author Topic:   Mercury Telltails
Wagon1 posted 11-03-2001 07:42 PM ET (US)   Profile for Wagon1   Send Email to Wagon1  
I repowered my 72 13 this year with a 2002 3 cylinder Mercury 40 (15 inch). It replaced an 82 35 Johnson. The Johnson always had a very steady stream of water coming out of the back regardless of whether I was trolling or at WOT. The Mercury will mostly dribble, sometimes stream, and sometimes not flow at all. Is this normal on the new Mercs? It makes me nervous.
Seattlerocket posted 11-03-2001 09:07 PM ET (US)     Profile for Seattlerocket  Send Email to Seattlerocket     
my 2002 Merc 2 stroke puts out a good stream all of the time
jimh posted 11-04-2001 08:08 AM ET (US)     Profile for jimh  Send Email to jimh     
I have an older Mercury engine (1976), and the confidence stream output appears to be taken from the water cooling jacket after the water has passed through some of the powerhead. I haven't actually traced the route, but I make this assumption because:

--the temperature of the water warms as the engine warms up;
--the water output takes a few seconds to appear after the engine starts and runs.

I also own a Yamaha engine (1987), and the confidence stream seems to be taken right off the pump output. I make this assumption because:

--the temperature of the water is always cold or lake temperature;
--the water output begins as soon as the engine cranks and often precedes the engine start.

Also, in the older Mercury the amount of flow in the stream varies with engine speed, and at low idle speeds it can be a weak stream, especially when running on muffs and not in the water.

In many of the newer Mercury engines, the stream seems to be much higher pressure and has little change in output with engine speed.

When I first saw my engine side-by-side with a newer Merc, I concluded my water pump must be going bad (since the stream output was so much lower) and I replaced the impeller. The new impeller did not change a thing. I asked my trusted Mercury mechanic about this and he cited a difference in the water pump design. The way my engine worked was typical of the older designs; the newer models used a different style of pump.

Mercury has a line of "classic" engines, which I interpret to mean "engineered long ago and proven to work" (as well as "tooling is still good so let's get some more engines out of this"). Perhaps the model you have is a "classic" Mercury 2-stroke engine. If so, the behavior of its water pump may be more like what I have described above.

In any case, I would be worried if the stream output stopped completely at slow speeds. That does not sound right.

Clark Roberts posted 11-04-2001 08:09 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Mike, some Mercs have the tattle tale stream in-line after thermostat so that no water flows until thermo opens and then stream is modulated by thermo opening and closing. I have a merc 20hp that is like this. When throttle is wide open the water press bypasses thermostat so the stream should be at full force at WOT. I have a 40 Merc that starts "peeing" when starter turns motor over (before engine even fires)... Check with dealer, mechanic or call Merc and find out what's normal for your engine (manual usually describes)... good luck and Happy Whalin'.. Clark... SCN
Wagon1 posted 11-09-2001 09:23 PM ET (US)     Profile for Wagon1  Send Email to Wagon1     
Thanks for the heads-up guys. Just got her back from the shop. They said they had to "blow her out" twice to remove some sand and silt. That kind of suprises me. I have gone through some silty water, but never grounded the engine, and always flushed her out after a trip (only about 15 hrs on the engine). My old Johnson could plow through a sandbar (don't ask) and not belch. Thanks again for the advice, I'm glad I brought her to the shop ($75 an hour, ouch).
FISHNFF posted 11-12-2001 01:12 AM ET (US)     Profile for FISHNFF  Send Email to FISHNFF     
Here is something that applies to my 90 4 stroke with a flushing port. The motor can be flushed via a hose fitting over the tell-tail. The water hose force pushes freshwater into the system, and the motor must be run for proper flushing. My complaint is the tell-tail shoots almost straight back, so the motor must either be cocked starboard or you must walk back to see it. On the Suzuki 70 4S, the telltail is adjustable so you can actually shoot it up in the air! Isn't a tell-tail made so you can monitor water flow through the engine and detect a potential problem?

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