More on Black Max. Water discharge this time

[Texasmark]

Seems on these V6 Mercs, the water from the heads exits via the thermostats, once they open (120F); that is, the water that's not diverted to cool the exhaust manifold which is there always; has to be or you would burn it up.

So they have a 3/8" tubing arrangement that sums the output of these two stats and delivers it to the lower part of the power head head where it is dumped in to the exhaust horn(s) in the mid section to go out with the exhaust gasses.

Teed off this, at 90 degrees, is a 1/4" to 5/16" rubber tube that goes to the pee outlet mounted in theside of the cowling.

So if you have one of these critters and have been wondering about a couple of things, I may have some answers for you.

1. Pee does not (can't) exist till the stats open (120F). I really don't like this as if you have an impeller problem or clogged water passage to the head, you won't know it till the over temp horn sounds at 195F regardless of when the stats open.

My 90 hp is a later model 3 cyl, and the pee comes directly from the exhaust manifold jacket; water is there always if the engine is running; much better for checking the impeller, but does nothing to catch a stuck stat till the OT warning goes off......seems they can't win for loosing. :%

------------

Back to the Pee outlet.

2. Since the tubing to the pee spiggot is much smaller than the tube from the stats, and since it's at right angles to the flow, and since there seems to be minimal restriction at the end of the stat discharge (for back pressure to assist the pee outlet), by definition you will have a weak pee stream......when you finally get it.

Just my observations.

Mark

 

[dingbat]

Re: More on Black Max. Water discharge this time

Not sure what motor your talking about, My 86 Black Max peed like a race horse from the moment it fired up, Always did since day one.

 

[Silvertip]

Re: More on Black Max. Water discharge this time

If the tell tale is supposed to be an indicator of water pump operation, even a brand spanking new engineer would not design a system that would not allow tell tale flow until the stats open -- but then again!!!!!! d

 

[gss036]

Re: More on Black Max. Water discharge this time

I think the t-stats on the V-6's are 143 degrees to open.
Not all Mercury engines are the same for the pee indicator stream. Some Merc's have a high pressure water pump that reaches 22psi, most have pumps that go to 12 psi WOT, such as my 89 200hp Black Max.

 

[Texasmark]

Re: More on Black Max. Water discharge this time

Interesting gss. I think I was on here shopping for stats for it and realized that they had several temps offered for these V engines. My inline 3 is an '02 and uses 120F.

The water coming out of this one when the stats open is definitely in the 140 degree range. It won't burn you, but you can't hold your hand in the stream.

Mark

 

[Texasmark]

Re: More on Black Max. Water discharge this time

Interesting gss. I think I was on here shopping for stats for it and realized that they had several temps offered for these V engines. My inline 3 is an '02 and uses 120F.

The water coming out of this one when the stats open is definitely in the 140 degree range. It won't burn you, but you can't hold your hand in the stream.

Mark

 

[Texasmark]

Re: More on Black Max. Water discharge this time

Hey Seahunter,

Would you mind taking a minute and answering a question for me? (Son's engine is a '95 150 2 liter BM.)

Would you pop your cowl and look at the routing of your cooling water hoses and tell us what they did in '86 on your ??? hp engine?

Thanks,

Mark

 

[Texasmark]

Re: More on Black Max. Water discharge this time

Looks like I got a double post. Sorry bout that. Got distracted....cat jumped up in my lap. :%

Mark

 

[dingbat]

Re: More on Black Max. Water discharge this time

Unfortunately I sold that boat back in June but here is what I remember:

The stats where 143 degrees and had a small by-pass hole in them. As far as the hoses, the two lines from the thermostat where teed and ran out to the pisser. I want to say that there was a hose running from the base of the block to the pisser as well but I’m not 100% sure about it.

If you believe you have coolant problems take a good long look at your poppet valve .I had a lot of problems with the poppit value sticking from time to time which resulted in more or less flow out the pisser depending on which position it stuck

 

[Texasmark]

Re: More on Black Max. Water discharge this time

Hey Sea,

Sounds like your routing is just like the son's. The Hoses are tied directly to the stats output and there is no additional hootus' to provide for bypass flow; least not on this engine.

I believe the 143 and the bypass hole. But like I said, the way it's plumbed, no way a small bypass hole is going to get you any pee due to the tube size and routing.

Thanks for you response.

Mark

 

[andy6374]

Re: More on Black Max. Water discharge this time

Silvertip I am going to have to respectively disagree with you on this issue involving mid 80's to early 90's black max's.
Like I said I can ONLY speak for these vintage Black max motors. Let's even say 200 and 225hp because that's all I've ever had or worked on. That being said (I've carefully covered all the ground here).....

You WILL NOT get a strong tell-tale until the tstats open. The tstats have bypass vents in them, so when they are closed you will get a dribble to a very weak tell-tale. At idle speeds you can actually watch the tell-tale get stronger and weaker as the tstats open and close as the engine warms and cools.

On other motors, YES, as soon as it is fired up the tell-tale will spit like hell which indicates the waterpump is working. But that's because the water routing for the tell-tale basically comes right from the watertube.

But on these vintage Black Max motors (or at least the ones I've seen) the tell-tale routing comes from the tstat housing on the starboard side. So it won't be strong until the tstats open.

 

[dingbat]

Re: More on Black Max. Water discharge this time

I did some digging around in the assembly drawing at Merc and found evidence to my belief that there was also a hose running from the exhaust plate to the pisser. The hose comes out of the exhaust plate on the left hand side of the motor looking from the back. The hose is then tied into the thermostat lines down and behind the cowling support bracket that holds the pisser.

 

[Texasmark]

Re: More on Black Max. Water discharge this time

Well great seahunter. That answers my question and explains why your stream was strong initially.

Really appreciate your taking the time to dig into this. Maybe I can help you out sometimes with my inquisitiveness on something.

Mark