Hi again,
so we were heading out yesterday and straightaway realised that there was reduced water flow from the exhaust so I turned round at the end of the finger and moored up again.
I had a look today (it's a Bukh 10hp) and after checking that the impellor is good (it was new couple of months ago) I thought I would check the exhaust for blockages and found that the exhaust flange has corroded away from the elbow which is a stainless custom piece.
I pulled off the blue plastic water mixer I think it's called and it had some rust pieces in that so I cleaned it out.
I've removed the flange and am thinking I can get it welded somewhere on the Sunny Coast with a new piece of pipe to either slide inside the ss elbow as it was or maybe to the outside as the inside of the ss elbow has the remains of the old pipe very securely stuck in it.
So I'm wondering is the diameter of the pipe off the exhaust flange critical or would it not matter if it was increased to go over the ss elbow rather than inside it as before?
And while on this subject does the length of the rubber exhaust pipe from the blue water mixer to the transom outlet affect engine power or economy? On mine there seems to be around 3 meters which goes up in a loop above the waterline, then down to floor level again and finally up again the the outlet? Does this seem a lot or normal?
If it was longer than needed would it be ok or have a negative impact on power?
cheers

So I'm wondering is the diameter of the pipe off the exhaust flange critical or would it not matter if it was increased to go over the ss elbow rather than inside it as before?

A small difference in the diameter of the exhaust should be no problem. If you are talking about a larger dia of pipe to slip over pipe that is already in the system, go for it. Most of the older engines allow a fair bit of flexibility when installing.

And while on this subject does the length of the rubber exhaust pipe from the blue water mixer to the transom outlet affect engine power or economy? On mine there seems to be around 3 meters which goes up in a loop above the waterline, then down to floor level again and finally up again the the outlet? Does this seem a lot or normal?

If that is how much exhaust hose is needed to get from the engine to the exhaust outlet in the hull, then it's normal.
If the above waterline loop was fitted by a previous owner I would accept it as a necessary modification.
You have a small engine that is pretty economical as it is and 10 HP is all you are ever going to get out of it.
Reliability is the number one factor to be looking for in a yacht engine. Not speed or power.

gary

You need to take that whole elbow to a good exhaust shop and get it rebuilt by the sounds of it.

I just figured out how to insert photos...

've removed the flange and am thinking I can get it welded somewhere on the Sunny Coast

Sorry cockpit san
Don't waste time or money on THAT flange. It is dead.
Buy a new original flange or at least price one and then do as Cisco has suggested. RIP.

Gary

The stainless water in elbow looks good.
You could buy a new iron flange or get one made in s/s with a bit of pipe zapped into it to which you could weld that elbow. The first bit of flex pipe is after exhaust cooling.
Stick with the blue plastic water trap.

That flange is usually cast iron and is sacrificial. It's meant to fail like that instead of some other expensive part.

As the main square part with the bolt holes is absolutely solid I thought I would just cut off the round pipe section and have a new piece welded on. I just wasn't sure whether to try and keep the same diameter and go inside the ss elbow or have it made larger to go outside...

I would get a new stub welded in the same size as the stainless elbow and join them with a short piece of steam hose.

Looks like it was a threaded joint and the steel part has completely rusted out and the ss thread has also coroded away. I would cut both old threaded parts off and weld new ones on. Commonly found plumbing fittings. Keep the mild steel part mild steel if stainless it might eat the manifold.

The beauty of buhk diesel is that you can still buy the parts you need. It wont be cheap but it will be easy to fix and if it goes again you have a standard part

I would just make a new flange from stainless and insulate it from the motor with a gasket.

If your installation allows the fitting of a one piece unit,, do away with the thread.

^^ Way to go Joe.

Ok, so I got the pieces welded up and they look fine.
I put them on today but am still getting an issue.
There has never been a great deal of water coming out the exhaust on idle but now is even less but still a bit. If I give it some revs in neutral it spurts plenty of water out initially then a bit less.
I wasn't happy with how it looked but temp was still ok so I took her out just around the marina and basically when she is under load most of the water stops coming out the exhaust and there is some dark grey smoke, not a huge amount and there seems to be plenty of pressure behind it (it doesn't come out in a cloud, more straight out and it's not thick smoke).
The temp was also rising, again not a lot but getting just over half and she would always be just over a quarter before this issue. It could have continued to rise I am not sure as I brought her back in.

Any ideas from the Seabreeze diesel mechanical team?
thanks

Ok the impeller is new, the raw water strainer is clean ? You can blow back down the intake and blow bubbles ? The heat exchange has been stripped and cleaned ? Belt driven pump ? Belt adjustment. Gear driven pump ? Is there a shear pin on those things ?
Appears maybe the nail in your old exhausts coffin could have water flow ?
Is it raw water cooled ?

So many questions !

Raw water cooled so no heat exchanger, new impeller and I think gear driven pump?
I read that maybe dark/black smoke can be caused by overloading like maybe something wrapped around the prop but would overloading cause lack of water flow?

I am also trying to think if we have used the boat since we hauled her out last and could anything have happened during or after the haul out to give these symptoms?

There wont be all that much water flow with this type of small engine. Pull off the hose after the water pump and start the engine and let the water run into the bilge. Just run the engine for 10 to 15 seconds or so and note the water flow. It wont be much. Re install and then do the same with the hose that injects the water into the exhaust. With a warmed up engine the water flow should be similar. You may have a calcium build up in the block or the thermostat and the bypass might be crook.
When you run the engine normally does the face plate of the pump feel cool to the touch?

Find a Youtube video of your engine or a similar engine and see how much water flow they have. Look at a couple of Barnacle buster videos and see how to remove calcium from the cooling passages.

Hi Cockpit
Cograts on the exhaust fix.

As to the cooling water flow problem.
Water in- water through- water out.

Water in.
Check inlet cock for blockage by plastic bag or sea life. Remove hose from cock and open.
Check line to strainer. remove at strainer and open cock.
Check strainer. Clean strainer and with top off open cock.
Check line from strainer to cooling water pump. Remove line at pump and open cock.
Water through.
As Ramona suggested . Remove line from pump and run engine.
Remove line into block and run engine.
Remove thermostat and check. A stuck closed thermostat will cause the engine to warm up excessively. (warm up!)
A stuck open thermostat will not show any real symptoms. But it is worth pulling it and having a look. New gasket can be made from corn flakes packet cardboard.
Water out.
Remove water outlet line (from block to exhaust inlet) run engine and check flow.
Check inlet nipple on exhaust is not blocked or restricted. Remove hole and poke nipple interior with a screwdriver.

If all of those things are clear , the only other thing that would restrict cooling water flow would be calcium/grunge buildup in the internal cooling passage of the engine block and head. That does not happen suddenly as seems to be your case.

You say" just over half and she would always be just over a quarter before this issue."
How many degrees are we talking about?

I would suggest that the cause, if not a blockage is, somehow , the impeller.
Wrong size?
Not fitted properly?
Slipping on shaft?

And lastly, hopefully , as you said, "There has never been a great deal of water coming out the exhaust on idle"
you don't really have a problem and are overthinking it.

All the best
gary

Select to expand quote

Cockpit said..

I am also trying to think if we have used the boat since we hauled her out last and could anything have happened during or after the haul out to give these symptoms?

May not be the case but sometimes when hauled out an air lock in the raw water suction line can develop if the line is drained.
Some travel lift operators will sometimes recommend closing the valve before being hauled out.
Check by disconnecting the suction line at the pump and establish there is a good free flow or siphon of water.

Cocky...My old engine was a 10hp Bukh. There was never much of a water flow, it just used to spit really,
but I didn't get an overheating problem. I did however get smoke blowing every time I throttled up, even
a gentle rev increase. The smoke only lasted until the engine got to the desired revs then disappeared but
that was coupled with slow starting ( it had to build revs before firing ) so I knew the compression was failing.
Ultimately I replaced the Bukh with a Beta 14hp twin. Everything increased dramatically, exhaust water flow,
power, revs. speed. No smoke of course and instant starting. The old Bukh had just got too tired.

Thanks for the replies guys.
Just to point out that the engine has always and still does start first time every time after only a few seconds cranking even when not used for a few weeks.
As I cleaned out the blue water collector entirely (so it was empty) there must be water getting through as I am getting some water through the exhaust and it has a distinctive sound when the water is not flowing and I do not have it now.
Impeller is definitely right as bought from Bukh only a few months ago and I double checked the size as the old owner left a spare which I fitted but was 1mm too wide which I found out one day when it jammed against the cover plate and I lost all water flow. The Coast Guard were doing training next to me and I got them to tow me in so no problem .

My main puzzle is the dark smoke which I have never had before...
but still water flow is not good either

When I am down in the next few days I will pull the pipe from the block to the exhaust and check water flow there as if it's there it must be going in and through?
Cheers

Cockpit
I too have a raw water cooled Buhk DV10.
I have been told they don't pump much cooling water. This becomes obvious when you remove the outlet line from the pump and see the orifice size is a lot less than the 1/2" id skin fitting, hose etc.
I checked everything as per the previous replies. I don't have an overheating engine. Only thing left to do is clear the buildup in the water jacket. When I replaced the zinc I had to chip away salt build up as instructed by the tech at Buhk to fit the new anode.
Next time I'm on the boat I will try and remember to video my water discharge and upload if my computer skills allow.

Select to expand quote

Cockpit said..
Hi again,
so we were heading out yesterday and straightaway realised that there was reduced water flow from the exhaust so I turned round at the end of the finger and moored up again.
I had a look today (it's a Bukh 10hp) and after checking that the impellor is good (it was new couple of months ago) I thought I would check the exhaust for blockages and found that the exhaust flange has corroded away from the elbow which is a stainless custom piece.
I pulled off the blue plastic water mixer I think it's called and it had some rust pieces in that so I cleaned it out.
I've removed the flange and am thinking I can get it welded somewhere on the Sunny Coast with a new piece of pipe to either slide inside the ss elbow as it was or maybe to the outside as the inside of the ss elbow has the remains of the old pipe very securely stuck in it.
So I'm wondering is the diameter of the pipe off the exhaust flange critical or would it not matter if it was increased to go over the ss elbow rather than inside it as before?
And while on this subject does the length of the rubber exhaust pipe from the blue water mixer to the transom outlet affect engine power or economy? On mine there seems to be around 3 meters which goes up in a loop above the waterline, then down to floor level again and finally up again the the outlet? Does this seem a lot or normal?
If it was longer than needed would it be ok or have a negative impact on power?
cheers

pm you

Success! (I think).

Thanks again for all the help especially Greg on the phone.
I managed to get on the boat today and after a bit of detective work found this:


This is the hose after the impeller pump which goes to a metal Y piece to the block and thermostat housing.
Obviously a build up of salt or calcium which would have taken some time to get like that I think as the plug was over 1 cm long and as can be seen was only letting through a tiny amount of water. The metal piece it went onto was the same. I'm amazed that I had decent water flow at all up to the current problem...
Anyway, a quick clear out and now she throws water out better than ever
I ran her on the dock in neutral and in gear (but didn't go to normal cruising revs in gear) and she seems great, no smoke at all. I will try and take her out tomorrow just to make sure she is good under load and normal revs but am keeping fingers crossed all is good now.
I am going to replace the water hoses with new while I am at it.

So if anyone is getting restricted water flow check your hoses...

Cheers

Select to expand quote

Cockpit said..
Success! (I think).

Thanks again for all the help especially Greg on the phone.
I managed to get on the boat today and after a bit of detective work found this:


This is the hose after the impeller pump which goes to a metal Y piece to the block and thermostat housing.
Obviously a build up of salt or calcium which would have taken some time to get like that I think as the plug was over 1 cm long and as can be seen was only letting through a tiny amount of water. The metal piece it went onto was the same. I'm amazed that I had decent water flow at all up to the current problem...
Anyway, a quick clear out and now she throws water out better than ever
I ran her on the dock in neutral and in gear (but didn't go to normal cruising revs in gear) and she seems great, no smoke at all. I will try and take her out tomorrow just to make sure she is good under load and normal revs but am keeping fingers crossed all is good now.
I am going to replace the water hoses with new while I am at it.

So if anyone is getting restricted water flow check your hoses...

Cheers

good to here,you will find that is the water level your raw water sits at when not eng not used leaves level of scale there.

Well done Sherlock!!

Good news Cocky. I never suffered that with my Bukh and I'm wondering how it got like that. I would have thought
the pressure of water coming out of the pump would have kept the pipe clear.

So I took her out today and gave her a good run around the Marina and all is good.
Not a wisp of smoke, perfect temp and Niagara falls out of the exhaust (well not quite ).
I enjoy learning new things and this is just one more thing that makes me more confident on the boat.
Cheers

Select to expand quote

samsturdy said..
Good news Cocky. I never suffered that with my Bukh and I'm wondering how it got like that. I would have thought
the pressure of water coming out of the pump would have kept the pipe clear.

Everyone gets a calcium build up. Does not matter whether it's raw water cooled or fresh water cooled, just happens in different places. As the calcium builds up in Cockpits pipe the impeller blades would just fold flat. Those water pumps don't handle pressure well.

OK Ramona I understand. I didn't get Cockpits problem but I did get a build up of zinc around the the engine
anode which I had to chip off to get the anode in. So now I've got a fresh water cooled engine where am I
likely to get a calcium build up and what do I do about it ??.

Hi Sam, the heat exchange is the place you will need to clean as part of maintanence, that's where the calcium will build up.