Another 9.8hp mercury cooling question

[mrmossman]

Yup, another cooling question! New impeller, all seals look and feel good, all lines are clear. I get exhaust puffing out tell-tale port but only drips of water. I have a seloc manual but no mention of a thermostat and I'm assuming there is none. When I blow water into water tube to powerhead I get water back out exhaust and tell-tale. Engine is an 84 in excellent shape, real clean, runs great. I'm an auto/bike mechanic but new to outboards. Almost seems like thermostat. I'm ready to get a whole new pump just because I can't think of anything else it could be. Should I be getting exhaust puffs out of the tell-tale? I can feel the puffs of air coming out. I've read so many posts my eyes hurt. I'm stumped. Thanks for your help.

 

[achris]

Re: Another 9.8hp mercury cooling question

An easy way to check if water is getting to the powerhead is to feel (carefully) the exhaust cover while the engine's running. It should be cold to the touch. If it's warm/hot, no water flowing up. If it is cold, then try clearing the telltale hose with a piece of stiff wire, or remove the hose at the block and see if you get water there. Some of those older engines don't have/need a lot of water at low engine speeds. You may need to get the revs up a bit for a decent stream to appear.

Good luck,

Chris........

 

[mrmossman]

Re: Another 9.8hp mercury cooling question

Chris,

My tell-tale is clear as a bell. It puffs warm exhaust out of it but only a couple of drops of water. Is it normal to get exhaust out of it? My experience in autos would say it had a blown head gasket or cracked head but I only know what Seloc tells me about outboards and it's not enough. To me, exhaust pressure here would cause backpressure and interfere with the water pump pressure but like I said, I just don't know if that's possible or
normal.

I pulled the lower end back off and the impeller and all else looks fine. Doesn't seem to be leaking water anywhere but I had water in the water tube. I get a good air flow and water flow (with hose) through the head (I was concerned about blockage also and checked all this when I replace the impeller)

By exhaust cover, do you mean the casing between the powerhead and lower unit? Do these motors have thermostats and if so where? I thought
if it had one, maybe I didn't run it long enough to get it to open or it is
stuck shut. I just didnt' want to run it too long if it wasn't cooling.

I'm testing it in a 50 gallon drum and even put it in gear at medium speed. As an ex auto mechanic, I bought the book and checked out everything I could think of and then read a whole lot of posts AND faqs before hollering for help
but I'm glad there's a place to holler.

Thanks for your reply Chris, I appreciate your help.

So many questions, so little time.

 

[Don S]

Re: Another 9.8hp mercury cooling question

Are you sure it's puffing out exhaust? I would bet it's probably steam from the very little water in the cooling passages.
Are you sure the water tube is actually connected at BOTH ends.
I have also had the tube plug up right where it goes into the bottom of the motor. You could blow air thru it, but very little (if any) water would would pass.

 

[mrmossman]

Re: Another 9.8hp mercury cooling question

Well, I finally found the "exhaust cover" in the book, and I hadn't felt it when it was running but will.

Yes it's exhaust and not steam. Starts puffing bluish smoke as soon as it starts. It's a pretty good puff too. Easy to feel it on your hand but no water at all. Yes, both the pick-up tube and output to the head are sealed tight. I even pressure tested it with the lower unit off and water sprayed into water tube with tell-tale hole plugged with cap but lots of water sprays out of
exhaust up inside lower housing. I'm assuming that this is how most cooling water would exit but I don't know for sure.

Thanks Don

 

[mrmossman]

Re: Another 9.8hp mercury cooling question

OK, with lower gearcase off, when I flush through either the tell-tale, the flush hole, or the water tube, I get excellent flow through all remaining openings AND exhaust. I put lower unit only, into bucket of water and when turning driveshaft by hand, I'm able to pump water out of the pump. It also pumps water out of the junction between upper pump housing and water pump base as there is NO gasket there and none called for in the parts diagrams, however I do get water to come up and out of the guide tube.

I flushed under pressure and no water showed up in either cylinder so I don't know why it's puffing exhaust out of the tell-tale (starts the very second the motor starts) but the back pressure can't be helping the water flow (another assumption)

My 5hp British Seagull has an archaic four blade metal impeller with no tolerances what-so-ever. There's enough room to walk around it and it pumps
water at an idle like a kitchen faucet. Yes, we've come a long way with
technology.

 

[Harker]

Re: Another 9.8hp mercury cooling question

Did you check the inlet screen and tube before the impeller to see if it may be plugged? sounds like water isn't getting TO the impeller. Also, when testing , make sure the water level is above the waterpump to prime it. It may be the gasket that goes under the powerhead , if it has a hole in it between passages, it could allow exaust into the water passages.

 

[achris]

Re: Another 9.8hp mercury cooling question

With the leg off, put a hose on the copper water tube, going up the driveshaft housing, and see if you get any water from the tell-tale. You don't need the engine running to do this, unless there is a thermostat in your engine. Some of these engines where produced with a thermostat and the tell-tale is the thermostat outlet. Have you check the exhaust cover temp with the engine running?

The thermostat housing, if you have one, is located at the top of the exhaust cover.

Chris.............

 

[mrmossman]

Re: Another 9.8hp mercury cooling question

Yes, I've pumped water up the water tube, in the flush hole and down the tell-tale and when I do all other holes blow water with no restriction at all. INCLUDING water out of the exhaust. No water leaks where the watertube
attaches to the powerhead but it pours out of the exhaust. It also sprays out ot the tell-tale, really good, and out of the flush out hole. There is definately no obstruction at all. Should it be spraying out of the exhaust
next to where the watertube attaches at the powerhead?

With just the lower end in a buck and a pair of vicegrips on the driveshaft, I can get it to pump water out of the output side of the pump by turning it by hand! I've had the screen, pickup tube waterpump all off.

I'm definately getting exhaust puffing out of the tell-tale. Starts out cool on start up and gets warmer as it runs. I haven't run it more than about a minute
at a time. And yes, it's stinky, blue smoke exhaust that comes out as soon as I start it up. I thought maybe a bad head gasket or head but when I sprayed back up the water tube to the head, I plugged the tell-tale to try and get water to maybe spray into the head and it didn't happen. It may well be a bad gasket at the powerhead, or elsewhere.

Initially I wondered about a thermostat but I don't believe it has one. Nothing at the top of the exhaust cover and water runs out the tell-tale when using a hose.

The only theory I have is that exhaust pressure entering the water line is
overcoming the water pressure from the pump.

The motor starts first pull, runs great, clean, no corrosion anywhere, hardly
used. I inherited it from my neigbor when he passed away and I know he was using it last year.

So, I just need to know whether;

1. Should any exhaust be coming out of the tell-tale normally with
the water?
2. Is it just the head that has the water jacket or the block too?

Then I will decide if I'm going to buy a complete new pump first or pull
the head first.

As I stated before, I've been an auto and Harley mechanic but this is my first outboard along with my british seagull. I had to rebuild the carb on that and make a new carb cap cover for it and clean out the water passages but it runs really great now. I only wanted it for a back-up but it's looking more like my primary every day.

I appreciate all your help and posts. I've read a lot of posts in here and you all seem like a good group of folks. No attitudes either. It's a pleasure
to be here. Thanks again.

 

[Laddies]

Re: Another 9.8hp mercury cooling question

Have you made sure there are no impeller peices or other trash in the lower pump intake and sealed the grommets in the pickup tube, as exhaust fills the torque tube it tends to be pulled in by the pump.

 

[Randy.C]

Re: Another 9.8hp mercury cooling question

I have 1985 9.8 merc and the same thing happens to mine, you have to make sure the whole lower unit is submursted into the water. Fill the barrel to the top. I believe this might solve your problem. I believe when you run an outboard in barrel the exhaust gets trapped in the in the barrel and goes up the water pump and you lose your prime , onlike in open water the exhaust gets blown clear of the motor.

 

[mrmossman]

Re: Another 9.8hp mercury cooling question

I have 1985 9.8 merc and the same thing happens to mine, you have to make sure the whole lower unit is submursted into the water. Fill the barrel to the top. I believe this might solve your problem. I believe when you run an outboard in barrel the exhaust gets trapped in the in the barrel and goes up the water pump and you lose your prime , onlike in open water the exhaust gets blown clear of the motor.

That just may be. Seeing as the pick-up is under the cavitation plate where all the exhaust bubbles are, it makes sense. I'll put it back together tomorrow and try it. I'm hoping I have the same problem you did. If you're correct, I'll buy ya a virtual brewski, Heck, I'll buy ya all one. Thanks

 

[mrmossman]

Re: Another 9.8hp mercury cooling question

Have you made sure there are no impeller peices or other trash in the lower pump intake and sealed the grommets in the pickup tube, as exhaust fills the torque tube it tends to be pulled in by the pump.

Yup, I've taken it all apart and everything is clear. I didn't seal the pick-up tube other than the tight fit the seal gives but everytime I take it apart it is
very firmly still in place with a tight seal. I think you may be correct about the exaust gases getting in the pump but maybe as Randy.C replied. I do notice all the exhaust gases bubbling violently directly under the pick-up tube. I'm checking it out tomorrow. Thanks for the reply. I'll post my results either way.

 

[achris]

Re: Another 9.8hp mercury cooling question

Mrmossman,

These engines don't have a separate head, it's cast integral with the block. What you see bolted to the top of the block is a head cover, just a water jacket cover. The block also has a water jacket to cool it.

Water out of the exhaust reliefs with the hose on the water tube is good. The last place the cooling water goes is the exhaust system to cool the gases as they enter the driveshaft housing. And I have seem many that puff exhaust gas out of the telltale, just before the block fills with water. The gas enters the block through the exhaust spray and will stay there until the water pump can fill the block and displace it, that's why you will be seeing exhaust from the telltale. How long have you let it run? Sometime it can take up to 30 seconds for the block to be completely filled and water to appear at the telltale.

Have you check the exhaust cover temperature with the engine running yet?

Chris.........

 

[mrmossman]

Re: Another 9.8hp mercury cooling question

I have 1985 9.8 merc and the same thing happens to mine, you have to make sure the whole lower unit is submursted into the water. Fill the barrel to the top. I believe this might solve your problem. I believe when you run an outboard in barrel the exhaust gets trapped in the in the barrel and goes up the water pump and you lose your prime , onlike in open water the exhaust gets blown clear of the motor.

THANK YOU, THANK YOU and THANK YOU, I'm absolutely amazed. It pees almost as good as I do after a twelve-pack! Leave it to Mercury to put the pick-up on the bottom of the cavitation plate. I raised the engine a few notches and turned it so the plate was at an angle to help run off the bubbles and filled it up. Works just great. On my British Seagull they warn NOT to overfill the barrel as the exhaust backpressure increases and doesn't help the motor run well. I'd like to thank Randy.C, achris, Laddies, Harker, Don S and all the others that read the post to see if they could help. I guess the pump worked so well that it was able to pump exhaust gases through it. The virtual bar is now open and I'm buying. Barkeep, a double for my new friend Randy C. Thank you all very much.