Only a trickle from the exhaust

[Impaler]

Today for the first time I ran my 1GM10 fitted in a Shrimper 21 out of the water using a fresh water supply. Normally I flush prior to lift out when afloat.

The engine was sucking water in fine, I use a funnel on a hose to the intake so I could see the level going down. However very little was coming from the exhaust. I have a Tidesmarine series One shaft seal and this takes fresh water from the water outlet of the engine. It is teed into the supply that feeds the exhaust elbow. It is a professional fit by Cornish Crabbers and in two years all worked fine when afloat.

There is a steady stream of water coming out from the prop shaft via the seal. I assume this is normal.

My question is: When afloat would the slight back pressure from the sea be sufficient to encourage more flow to the exhaust elbow rather than most of it going out through the shaft seal? Perhaps this is exacerbated by pressure from the exhaust at the elbow encouraging water to take the route to the seal.

Any ideas? Thanks.

 

[MikeCC]

In the absence of being able to do much else at the moment, I'd get the elbow off and have a look. How long since it was last replace or cleaned out?

 

[Impaler]

It’s only two seasons old so it should be OK, may have a look inside. Luckily the boat‘s in the garden.

 

[MikeCC]

Another thought, can you easily isolate/block the feed to the shaft seal?

 

[Impaler]

I’d thought of that but I’d need to disconnect and plug the feed which I don’t really want to do. Getting these hoses off is a bit of a nightmare in the confined space. Worst case is to get her afloat (one day!) and see what happens.

 

[V1701]

There can't be more going in than coming out though, unless there's a leak somewhere and it's draining in to a bilge or something...

 

[Impaler]

Thanks all, I’ll probably disconnect the feed to the seal and give it a whirl.

 

[Impaler]

Thanks all, I’ll probably disconnect the feed to the seal and give it a whirl.

 

[PilotWolf]

I’d thought of that but I’d need to disconnect and plug the feed which I don’t really want to do. Getting these hoses off is a bit of a nightmare in the confined space. Worst case is to get her afloat (one day!) and see what happens.

Aa an aside I would consider fitting a valve somewhere in the line in case you have a leak.

W

 

[davidej]

With the boat in the back garden, could it be that the shaft feed is the line of least resistance? If it were in the water the shaft tube would be full of water creating significant back pressure.

 

[James_Calvert]

I think that was the original poster's question!

 

[Bilgediver]

Is it possible that your cutless bearing is worn as this could effect the balance of the system and so reduce the output from the exhaust

 

[Buck Turgidson]

according to their website the seal needs a gallon a minute! Not surprised there isn't much coming out of the exhaust.

 

[Portland Billy]

The water is taking the path of least resistance. Once back in the water things should revert to normal.

 

[Impaler]

The water is taking the path of least resistance. Once back in the water things should revert to normal.

That's my hope, suspect you're right. As it's only two years old with 35 hours running I don't think it's wear and tear.

 

[awol]

Can't you just squeeze the shaft seal feed-pipe to restrict flow? Mole grips with soft jaws (bits of wood?) would do it.

 

[Impaler]

Can't you just squeeze the shaft seal feed-pipe to restrict flow? Mole grips with soft jaws (bits of wood?) would do it.

That sounds scary, don't want to damage anything. I thought that I might try some masking tape round the shaft outside to see if it restricts flow.

 

[awol]

That sounds scary, don't want to damage anything. I thought that I might try some masking tape round the shaft outside to see if it restricts flow.

You're not trying to squash it flat, just restrict it. Old people like me have tools for squeezing brake pipes to avoid losing all the fluid while changing cylinder seals on BMC cars.

 

[vyv_cox]

I would be surprised if an immersed shaft would reduce flow through the seal to any significant extent. The back pressure is only a couple of inches water head. My money is on a blockage in the elbow.

I would also clamp the seal hose but I suspect this may not identify the problem. The seawater pump provides plenty of pressure, which will drive water through the elbow when the alternative route is blocked

 

[Impaler]

You're not trying to squash it flat, just restrict it. Old people like me have tools for squeezing brake pipes to avoid losing all the fluid while changing cylinder seals on BMC cars.

Actually that makes sense. I’m sure that I have a G clamp that would do the trick. I’ll report back!