Hello all,
I have a sailing boat with a 1990 (white) 4-stroke 9.9HP Yamaha outboard that sits in a well in the cockpit.
At the end of last season I had a problem that when I started the motor there was sometimes no tell-tale water. I could get the water to come through by sucking on the tell-tale tube, after which no problems; plenty of tell-tale water & not hot at all.
This got worse & when I lifted the boat out the inlet water grills were fouled so I thought this was the problem & cleaned out the inlets.
When I put the boat in again this year, after running with those 'earphone' thingies & a hose pipe whilst on land for half hour or so, there was no problems motoring round the couple of miles to my berth.
But then the next time I tried to start the engine, no tell-tale. I got it coming through again by blipping the throttle & if that didnt work then blowing & sucking on the rubber tell-tail tube & once water is coming through no problems at all.
Since then, it has been an completely intermittent problem: Either strong tell-tale & cool running or no water & I have to mess around with it until I get water out, but even then no problems at all once it is coming through.
I have been pointed towards impeller, and although I think this needs to be done, I don't understand how a damaged or worn impeller could give such an intermittent problem - I would have thought if this was damaged then it would always be running hot or with reduced flow, not either nothing or perfect depending on temperament as seems to be the case at the moment. (I do have an Engineering background & used to work for dad as a car mechanic) BUT I don't know much about outboards so am all ears to learn.
I thought of the thermostat sticking shut as a possibility (although is the tell-tale independent of this?), and have also had suggested that there is sand (could be mud as last year in drying mud berth) inside which needs blowing through with compressed air.
So please can someone explain this intermittent behaviour to me as I don't want to change the impeller just to find it is something else.
Thanks in advance for any help
I have a sailing boat with a 1990 (white) 4-stroke 9.9HP Yamaha outboard that sits in a well in the cockpit.
At the end of last season I had a problem that when I started the motor there was sometimes no tell-tale water. I could get the water to come through by sucking on the tell-tale tube, after which no problems; plenty of tell-tale water & not hot at all.
This got worse & when I lifted the boat out the inlet water grills were fouled so I thought this was the problem & cleaned out the inlets.
When I put the boat in again this year, after running with those 'earphone' thingies & a hose pipe whilst on land for half hour or so, there was no problems motoring round the couple of miles to my berth.
But then the next time I tried to start the engine, no tell-tale. I got it coming through again by blipping the throttle & if that didnt work then blowing & sucking on the rubber tell-tail tube & once water is coming through no problems at all.
Since then, it has been an completely intermittent problem: Either strong tell-tale & cool running or no water & I have to mess around with it until I get water out, but even then no problems at all once it is coming through.
I have been pointed towards impeller, and although I think this needs to be done, I don't understand how a damaged or worn impeller could give such an intermittent problem - I would have thought if this was damaged then it would always be running hot or with reduced flow, not either nothing or perfect depending on temperament as seems to be the case at the moment. (I do have an Engineering background & used to work for dad as a car mechanic) BUT I don't know much about outboards so am all ears to learn.
I thought of the thermostat sticking shut as a possibility (although is the tell-tale independent of this?), and have also had suggested that there is sand (could be mud as last year in drying mud berth) inside which needs blowing through with compressed air.
So please can someone explain this intermittent behaviour to me as I don't want to change the impeller just to find it is something else.
Thanks in advance for any help