Outboard Exhaust from tell tale hole, help.

[seumask]

I must admit firstly to having had this engine in pieces, to respray the bottom cowling and leg. It is a 1984 2 stroke Yamaha 8 with the following symptoms. Approximately 2 to 3 mins after start up water stops coming out of the tell tale hole and exhaust gasses come out. The engine then seems to be on its way to over heating and gets very hot, at which point I have stooped it running before I do any real damage to it. I have had the power head off and replaced this gasket. I have also put a new impellor in it and this seems to be pumping water well. Can any one recommend any other action before I give in and take it to the local dealer for open wallet surgery?

 

[snowleopard]

I suspect the 'exhaust gases' are in fact stem resulting from the water in the jacket boiling. That would be a result of inadequate water flow.

If they truly are exhaust gases it's a head gasket or worse still a hole in the water jacket from the cylinder.

 

[seumask]

It seems to be exhaust gas as it is tinged blue grey.

 

[tross]

First question - was it OK before you removed the leg?

 

[Lakesailor]

Have you read (shush) Sailing Today this month. It has an impellor replacement article for a Yamaha (9.9 4 stroke). Don't know if that helps. It does mention the woodruff key in the impellor shaft. If that's missing it may explain why water stops coming out of the hole when the motor warms up.

 

[Pye_End]

I had this on a 1979 Yamaha 8. Had open hart surgery after the head gasket blew by a main dealer, and that is when it all began.

In hindsight I should then have consigned it to the bin and bought a new one.

There is nothing worse than ferrying it out to a mooring on an inflatable, struggling to get the thing on without it finding its way though the dinghy to the deep, ready for a week's holiday only to find the dealer has not got it right and the thing overheats again.
Think on mine the water flow was reduced for some reason, and after a while it all got a bit hot and steam came out the back.

 

[seumask]

Unfortunaly I think it was OK before I removed the leg and power head, its a real brain ache. Removing the powerhead meant breaking the power head to leg gasket , hence I replaced it. I'm failry sure there is nothing particularly wrong with the cylinders, engine runs fine, spark plugs good and clean as normal. Impellor and housing all inspected and checked carefully no obvious problems here either, pumps water well initally, i.e lots comming out.

 

[VicS]

Since these problems started when you separated the leg and power head you should concentrate on the possibility that you did not get someting back together properly. I am not familiar with the Yamahas but how certain are you that the cooling water pipe from pump to power head is correctly located. Are there grommets or other connectors at the top and/or bottom that may be damaged or displaced? I would take the lower unit off and be sure that I could get a good flow of water from a hose up to and through the engine. (I would take a look at the thermostat as well.)

In my experience you have to take the lower unit off first then remove the power head did you do it this way or did you simplty take the powerhead off?

The iBoats forums are good for advice on outboards. They are covered make by make but if you go there with your query state the year/ model number at the outset. http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi

 

[Thistle]

Still have vivid memories of a gas fitter (pre-Corgi, I think) replacing a gasket on a cooker tap and being most concerned when no gas came through. Turned out that the new gasket went right across the gas supply hole. Could something similar be happening and restricting the flow?

 

[ex-Gladys]

I don't know this particular engine, but power head gasket upside down and blocking a cooling duct would be my favourite. I assume roughly the same parts that came off went back?

 

[totopalm]

I think Vics is on the case, i took the leg off my chrysler
outboard. put it back on and hey presto! NO water out
of the exhaust, so off wih the leg for a looksee and there
was the cause thecopper pipe from intake to pump had
to penetrate Ohh! the pick up pipe to engine i had managed
misalign it, Thats what i would look at first
Cheers Tony

 

[seumask]

Thankyou for all the suggestions, I thinks its off with the powerhead again and a carefull inspection of the gasket. Looking carefully at the engine parts diagrams on yamahaoutboardparts.com it appears that around the year of this engine the gasket changed slightly with older ones having an extra hole, I think I may have fitted the wrong one.

 

[jaycee]

hi,i replaced the impellor on my mariner 4hp.last year.a couple of checksyou might make 1]is the water intake at the bottom of the leg free of any obstruction?2]is the connector from the intake to the telltale hole connected and free of any kinks?
i feel it should be one or both of the above.

 

[bdsweeting]

One thing also to check possibly... I watched a guy leave his o/b ticking over after starting it up and the tell-tale stopped and changed to steam.

When informed he revved the engine to restart the water flow. I think the problem was the water inlet was picking up exhaust gases from around the water inlet due to the low revs in still water.