too much cooling water!

[tbird24]

my tohatsu 9.8 (2 cycle), after setting for many months, started fairly easy, but not only was there a good flow from the cooling water check point, there was an extreme amount coming from the idle port. i have the parts manual, but the pics of the head & block are of little use for shining a light on the proper path of the cooling water. anyone know what would allow such a large flow from the idle port?

tom

 

[pvanv]

The vast majority of cooling water exits with the exhaust, through the prop. If you are very deep in the water, I would expect more from the idle port than if higher in the water. Check temperature with a handheld IR thermometer. Odds are you are fine.

 

[tbird24]

paul, thanks for the reply, but i think i must have done a bad job of explaining. i'll give it another go.

i just picked this unit up from a fellow who hardly ever used it. he kept it stored on the back deck of this power boat. problem is he never flushed it with fresh water after using it in the ocean. to add to that, it was laying down (resting on the area of the hood release and planing fin [prop down] on the foot [just above the water intake]). in this position, the cylinder head (item 1-6 in your parts manual) was parallel to the deck. my fear is saltwater that remained in the block settled in the lowest place an eat a hole in a water passage. when i say "an extreme amount", i mean 90+% of the water pumped by the water pump! i have my doubts any water was exiting through the drive shaft housing (leg) to the prop.

as for temperature, i only ran it long enough to use up the fuel in the carb that i filled from the fuel tank just to see if it would start, which it did easily and sounded good. this only lasted a few minutes, but during that time, water from the idle port had a stream of about 3/8" (or bigger) in diameter. if the water from this port had been coming out at an angle (like from the cooling water check point) and not staying in the bucket, i'm sure it would have emptied the bucket or at least lowered the level below pickup height.

do you still think "Odds are you are fine."?

i suspect my next move is to remove the head and inspect the thermostat/housing and the block. a water flow diagram would be very helpful.

tom

 

[Sea Rider]

Remove thermostat and check its condition, probably extremely salted or near jammed. Did you test the engine on muffs, barrel, at sea, lake whichever ? When water is hotter, you'll see more water coming out from idle port than when colder.

To check if thermo is working ok, put your hand on idle port exiting water and feel if water heats/cools accordingly. If stays at same temp, probably thermo is already kaput. For peace of mind knowing PO was careless, install a new thermo and voil?.

Happy Boating

 

[tbird24]

Sea Rider, thanks for your input, but it is not much help at this time. maybe, again, i didn't make myself very clear. before we look at the thermostat, we should at least feel the basic operation is working. i don't believe this to be true with my unit. as i said above, "... it would have emptied the bucket ." i have never seen that much water coming out of that port, under any condition. have you?

this maybe of help later....... " When water is hotter, you'll see more water coming out from idle port than when colder." to be clear, are you saying the hotter water is caused by the engine running or just ambient temp of water? and by "more", do you mean a stream or just a heavier sprinkle?

if you know/have the water flow route, it would be helpful to me. please pass it along. i suspect a blockage next to the exhaust port or an unnatural by-pass of the return to the leg (dumping it out through the idle port). i suppose either way i will end up taking the head off to check the thermostat.

thanks again for your time.
tom

 

[Sea Rider]

Some issues,

Don't have it clear where are you running the engine ? at sea when lower tail picks warmer water will see more water flow though idle port compared to much less when colder. There's a hanky panky going on thermo sensing water temp into powerhead, if thermo would release huge amounts of cold water through idle port, powerhead will work too cold..

Have you checked water warm/cold cycles on palm, this will indicate thermo cond and if working ok. On my 2 strokes if water intake is warmer will see more water flow coming through idle port, much less when water temp is cold and that's even at speed. About same flow when on muffs or barrel at idle + warm/cold cycles feel. Is engine peeing ok ?

What is your concern, is engine overheating ? If not. go for a wot spin and let water going throughout the entire cooling passages do its homework rinsing, cleaning all water passages.

Happy Boating

 

[TOHATSU GURU]

The idle port, on the rear side of the motor leg, will produce quite a bit of water at an idle as there is not enough pressure to force it down through the prop. It would be unheard of for any kind of corrosion to cause an abnormal of water to come through there. IE You do not have a problem.

 

[tbird24]

today was quite an eye opener! since the thermostat was almost for sure going to be clogged/frozen, i decided to go ahead with the head removal. only broke 2 bolts. sure enough, it needed attention. to check path of water to idle port (strange name for what it is) i blew smoke (cigars work well for this) into the port. without delay, it came out the small hole (exposed once head was off) at the bottom of the case below the 2 cylinders. this hole mates up to the hole at the bottom (not shown in parts manual) of the head. this has a straight shot up through the molded in tube on the outside of the head to the port that covers/encases the thermostat, on the head side. the thermostat was open (still haven't tested it yet), so water could flow freely to the idle port.

i have an 18hp nissan too. just for kicks, i had a close look at how the idle port worked on it. to my surprise, when i throttled up (engine still warm from previous run), that same large water flow came out of it too. it makes sense that when i first start the engine for the day, not much water would come out of the idle port due to the thermostat being closed until the engine warmed up enough to open it. i was always satisfied i had proper water supply as long as the pee stream was good. as long as it was flowing, i would never look at the idle port, so i never knew how much water could come out there. i'm still not clear how the water gets to the prop. i suppose as long as the leg is not getting excessively hot, water is moving out with the hot exhaust gas. i guess i'll find out when i get it put back together.

thanks for the comments. they helped keeping me on the project.

tom

 

[Sea Rider]

Once cooling water has made its voyage through cylinder head will be inmediately discharged down through the exhaust system and out prop it goes. Helps to cool lower leg exhaust system too. What was the removed thermo cond ? rusty, excessive salted, if, so put a new one. Will need a new head and lower pan gasket when assembling back power head..

Happy Boating

 

[tbird24]

i didn't take the engine out of the pan, so no gasket needed there. the thermostat was pretty cruddy. cleaned it up and put it in a pan of water and turned up the heat. no movement. will pick 1 up when i get the head gasket. still trying to get the broken bolts out. they are being stubborn.

other than the molded-in pipe on the outside of the head, there doesn't seem to be any other passages for the water passing thru the thermostat to travel in. it looks like the head shares the same water around the cylinders. using the parts manual...

http://www.tohatsu-nissan-parts.com...s Catalog M8B-9.8B (2011) - (00221030-7).pdf

gives only a few clues to the actual water flow. the 2 gaskets that sandwich the lower cowl (some call it the pan, fig.11) show water port openings. in fig 7 we see gasket #3. i see 4 water associated holes. one for the feed from the pump, one for the cooling water check port (small hole next to the dowel pin #4, pee stream), one for the idle port and the last i can't really say how it is fed or know how to call it, but believe it is the path of the heated or excess water to exit through the leg to prop. in fig 1 we see the 2nd gasket, #35. this gasket has 2 water ports that i can explain. the feed water from pump and the idle port. the larger openings to the side and aft of the exhaust pipe opening could allow the water feed to simply go across from the feed to be dumped into the port to the leg. without seeing that side of the case, i can only guess.

so, from what i see with the head off and the pics in the parts manual, i have to come to the conclusion the water that passes through the thermostat never sees the prop by way of the leg.

having said all that, looking closely at the drive shaft housing #1 in fig.7, the idle port and the (for a lack of a better word) leg port may not be separated totally. if so, this could allow a small amount from the main feed to exit the idle port, thus altering my statements above to some degree.

again i say, it would be nice to have a water flow chart of this engine.

tom

 

[Sea Rider]

There's usually a water path labyrinth on engine pan, part of the water outing lower power head is discharged through peeing hole, some out thermo and down through lower leg. If old thermo is shot opened, there's your a lot of water comming through idle port. Take advantage to manually decarbon piston head and head if needed, replace thermo, torque head to 30 NM, put 2 new plugs and voil?. Go out and have some fun. Probably will need to got to a machine shop to have both PITA broken bolts proffessionally removed...

Happy Boating

 

[tbird24]

Sea Rider, i think i get confused with your post because you use names for some of the parts that make me not sure what they are. if you can use the parts manual to give figure and item #, i think i could fallow better.

"some out thermo and down through lower leg." from my inspection of the outboard, with the head (fig. 1, item #13) off, there is no path to the leg from the thermostat (fig. 1, item #18). i guess if what looks like a partition (see fig. 7, item #1) between the idle port and the leg port (?) isn't really a partition but just a reducer to restrict the amount of water to the next port (in either direction), then that could allow a path for water to exit through leg as well as the idle port. it is hard to tell from the pic.

to be honest, i'm still not sure what the purpose/advantage of the idle port is.

btw, no carbon build-up in this engine. even though it is old, it must not have very many hours on it.

if the heat on the broken bolts doesn't work, i'll try (maybe) to arcweld a nut to them. this usually creates more heat where it is needed and with the new hex to put a proper wrench on, the bolts may just turn out (with a little help from wd-40). keep your fingers crossed!

Thanks for staying with me!
tom

 

[pvanv]

Idle ports are used to relieve back pressure at slow speeds. As RPM comes up, scavenging occurs at the prop... but at idle, the exhaust has to push out against the column of water. The idle port relieves that.

The thermostat only diverts water through the head passages. Otherwise, water cools the rest of the motor whenever it is running.

 

[tbird24]

Paul, i don't know how to reply to your statement without sounding offensive. that's the last thing i would want to do, but i don't see how it would be possible. am i missing an exhaust port that is above waterline?

"The thermostat only diverts water through the head passages." as far as i can see, feel, touch, there is only one passage through the head and it goes to the idle port. granted it can carry a lot of heat with the water, but i believe its main purpose is to allow a flow of water to pass the upper end of the case. you wouldn't want stagnant areas anywhere in the cooling system except to get the engine up to a good working temperature, right?

"Otherwise, water cools the rest of the motor whenever it is running. " i think i'm having a Yogi Berra moment.

would you like to try again?

tom

 

[Sea Rider]

Tom,

Why are you so obsessed about cooling water paths, the engineers who made that portable have it all resolved for that engine, If engine pees right, idle port does so, can feel warn/cold cycles outing water on your palm and engine runs as a champ why worry.

One issue that have not tried yet as don't have issues with cooling passages, is to put my palm against water exiting through prop and check if changes temp as the thermo does. If not, should be the cooling passages of the powerhead discharging through prop and head water discharging through thermo's back idle port circuit.

Happy Boating

 

[juanrescar]

gentleman, may i please ask a question of the same topic but bigger motor. I looked at a Pontoon Boat with a 70hp Tohatsu M70A2 today, the moter looks as it was running great plenty of water comming from the exhaust and prop but didnt know about the small port, untill reading it in the ownes manual, i didnt notice any water coming from there, but the motor ran for about 2-3 mins max. my question Motor out of the water with the foot adapter waterhouse hooked up, how long does it take for the water to come thru the small side hoe?? is that water exit for the thermostat?? Havent bought the boat but leaning towards buying it.just curious if the motor had to warm up more before water coming from there. Thank you for your reply.Juan

 

[pvanv]

This really should be in a new topic/thread, because it is a different issue on a different model...

The telltale is supposed to flow any time the motor is running. May take a few seconds to fill the water gallery but that is all. Telltales are famous for clogging, so yours may need to be cleared with a stiff wire while the motor is running. Ear muff flushers are also famous for not providing enough water to the motor.

The 70A2 is obsolete, but you can still get a new impeller if needed.

 

[pvanv]

Paul, i don't know how to reply to your statement without sounding offensive. that's the last thing i would want to do, but i don't see how it would be possible. am i missing an exhaust port that is above waterline?

"The thermostat only diverts water through the head passages." as far as i can see, feel, touch, there is only one passage through the head and it goes to the idle port. granted it can carry a lot of heat with the water, but i believe its main purpose is to allow a flow of water to pass the upper end of the case. you wouldn't want stagnant areas anywhere in the cooling system except to get the engine up to a good working temperature, right?

"Otherwise, water cools the rest of the motor whenever it is running. " i think i'm having a Yogi Berra moment.

would you like to try again?

tom

That is only the colling passage through the head. There are other passages as well. Not to worry; I wasn't offended. Not a problem that you don't understand every nuance of the cooling system... they work very well. As Luis noted, the engineers have it cooling properly. The 9.8 is a very durable design. Once you have any salt/silt clogs out and a good stat in, the only regular cooling maintenance will likely be regular flushing with fresh water and wp kits as needed.

 

[Sea Rider]

Just to confirm, while engine was water muffed while on, the water exiting through the prop was less warm that the one exiting through idle back port, so this kind of confirm that water cooling cranckase exits through prop and water cooling cylinder head exits through idle port. All 3, cranckase, idle and peeing port temps are not same, being peeing the coldest.

Happy Boating