Author Topic: Overheating Engine remedy. (Read 10009 times)

joepmay · « **on:** April 27 2012, 15:32 »

Hi, I have a problem with an engine overheating and reckon it is due to a blockage somewhere in the Saildrive intake. Just looking for suggestions as to the best way to try and resolve this. Should I be attempting to come up the Saildrive with some sort of wire or should I be trying to backwash the system from the opposite end?

Regards,

Joe.

njsail · « **Reply #1 on:** April 28 2012, 03:42 »

If you have access to a garden hose hook it up to the raw water intake on the leg and flush the leg. This should help blow any junk out. You can fill a bucket and dip the raw water intake in the bucket and start the engine to see if the blockage isn't in the leg and resides somewhere else.

dawntreader · « **Reply #2 on:** May 09 2012, 19:22 »

I had similar problem but it was junk in the heat exchanger that had by-passed the filter and was restricting water flow. Remove the 3 bolts at the front and have a look, there's nothing to replace so it won't do any harm.
Regards,
Jim

BillGiles · « **Reply #3 on:** June 26 2015, 20:36 »

We had a limited flow and a threat of overheating. After much though we held a bright light behind one of the hoses after the raw water pump and noticed a stream of bubbles. After tightening the raw water filter cap the bubbles ceased and the temp stabilized at a normal level.

Salty · « **Reply #4 on:** June 27 2015, 09:10 »

I too had a similar problem on my B36 which I'd bought secondhand some four years earlier. As Dawntreader mentioned in reply no 2, it turned out mostly to be an accumulation of bits and pieces at the entrance to the heat exchanger. Until last year I'd not opened up the heat exchanger, though I had personally checked the sea water filter and had always changed the raw water impeller myself, noting every time that the filter was clean and the old impeller was intact. Inside the heat exchanger I found several pieces of impeller blades, presumably from the previous ownership, plus pieces of shell from marine creatures. Spread out, there was almost enough to completely block the entrance to all of the tubes. The pieces of impeller and shells were all removed. The size of the shells however, were noticed to be larger than would fit through the openings into the saildrive leg and indicated that creatures had probably got in during the early part of their life and had grown before eventually being sucked through. This suggested to me that it was likely that other such creatures may also exist within the saildrive leg, so back in the marina I connected a fresh water hose to the pipe from the saildrive sea water inlet and back flushed the system to sea for about half an hour. This made sufficient difference to allow the engine to be properly cooled, but I also bought a long but small diameter bottle brush off eBay, and next time the boat was out of the water this was used to good effect to clean the intake on the leg. In addition I used a pressure washer pointed through every opening on the sail drive leg in order to remove some pretty stubborn creatures that didn't want to leave voluntarily, and so far this season have noticed that the flow of water through the system has been much more than it ever was before. The design of the raw water filter, presumably fitted from new, is a poor one where there is an opening in the side the removeable part of the filter. It appears this was designed to fit around some shape within the filter housing, and mine was slightly warped such that it didn't fit too well, presumably allowing the creatures to get in in the first place. I've not yet changed that filter, but it's on my list to be done.

BillGiles · « **Reply #5 on:** June 27 2015, 10:27 »

I have found mussels in the strainer which could not have got through the mesh other than as egg. One was around 12mm long! It seems a good idea to be more thorough in clearing the water channels on the leg when the opportunity arises. We have not had the intercooler apart for a while so that might be worth a look see at some time. The other place where debris gets stuck is at the anti-syphon valve which is pretty easy to get to and should be serviced (only cleaned and inspected) annually anyway.

Salty · « **Reply #6 on:** June 27 2015, 11:12 »

BillGiles is right, and as a further observation (wonderful this hindsight business !!), if you buy a secondhand boat, it's worth pulling the end cover off the entrance to the heat exchanger to check that nothing is there that should not be there, and preferably before heading out for that long distance adventure.

abouttime · « **Reply #7 on:** June 27 2015, 22:46 »

I had the same problem(s). As the boat was in the water, I took off the hose by the intake sea cock and attached the outlet end of the dinghy pump and gave a few good pumps to see if I could hear the air escape through the leg. Partially successful, I then bought a 3m drain unblocker - a piece of wire with a corkscrew end and send that down. Obviously, you need to be a bit quick to shut the seasick to avoid a rush of too much water. In my case, quite a lot of gunk came up as I withdrew the wire, and the flow out of the sea cock was noticeably better. But I still had insufficient water exiting the exhaust. Eventually, I discovered that the raw water filter was leaking air - it needs to be a vacuum. This big black plastic piece of badly designed nonsense is easy to cross thread or mess up the neoprene gasket. I just bypassed the filter, running raw water straight to the Impellor. The result was gallons of water exiting the now nicely cooled engine exhaust. I'll get round to replacing the filter but I've met a surprising number of people since who never bother with the filter at all, preferring, if necessary to change an Impellor if any nasty stuff reaches it, rather than risk engine damage through gradual overheating due to water starvation.

Ripster · « **Reply #8 on:** June 28 2015, 15:10 »

Just serviced my engine (D130F) and included a raw water heat exchanger clean. My estimate is that I had a 20% blockage, so it needed doing. Followed dawntreaders excellent instructions including sourcing new seals. Easy job and one that is very necessary.

Moodymike · « **Reply #9 on:** June 28 2015, 16:46 »

When you removed the heat exchanger stack did you have to drain the freshwater system?

Ripster · « **Reply #10 on:** June 28 2015, 18:24 »

As it happened I was changing the coolant anyway, so it was drained, but to clean the tubes (as DT indicates) you only need to take off the front end so there is no need to drain anthing. Unhook the coolant tank and rest it out of the way. Take off the main raw water pipe, remove the allen bolts and gently ease off the plastic end cover. you'll see the O'ring seal which is prob worth replacing. Then you have access to poke a suitable probe up each tube and clear it out. I used a suitable sized zip tie. Anything you push through and out the other side will flush away through the exhaust on start up. I was very surprised at the amount of carp that was there considering there is a filter in place. All in an easy job that takes a few minutes to do.

Moodymike · « **Reply #11 on:** June 28 2015, 18:26 »

I presume the coolant that is in the expansion tank and top hose you let drain into the bilge?

Ripster · « **Reply #12 on:** June 28 2015, 18:33 »

On mine, the coolant tank is on a mounting that allows it to be lifted off and lowered out of the way without disconnecting or draining anything. The pipes are flexible enough. To just clean the tubes all you get is little raw water from the pipe and tubes - but not much.

CRYSTAL · « **Reply #13 on:** June 29 2015, 17:18 »

Has anyone attempted to flush the coolant side of the engine and heat ex for proper cleaning the engine without removing the heat ex? I had to remove my H/E as it had accumulated a layer of thick film .

How can we flush the guts of the engine?
A small pump with 10% acid solution and let it recycle or can this damage engine or aluminum or seals?
BTW very carefully as need to bypass the exhaust elbow! !!
Tnx.

BillGiles · « **Reply #14 on:** July 02 2015, 22:30 »

I have heard of people doing away with the leg intake entirely and having a through hull fitting to the inlet. This seems to me to get away from the dodgy water channels in the leg but I am not sure if it is at the expense of some cooling, although the intake is above the bottom gearbox and below the main gearbox. This does have the advantage of avoiding the 'plastic bag around the leg' scenario. Although I once had a plastic sheet across the skin intake of another boat.

Impavidus · « **Reply #15 on:** July 05 2015, 14:43 »

Simple way to clear the sail-drive;

1. Open the raw water filter.
2. Open the sail-drive valve.
3. Push the end of your dingy inflator hose into the inlet side of the raw water filter (you may or may not need the adaptor fitted to get a good seal)
4. Connect the inflator hose to the foot pump.
5. Pump vigorously. Until the compressed air exits the sail-drive from the inlets on the sides and bottom of the casting.
6. Pump some more!
7. Close the inlet valve, remove the hose and replace the raw water lid.
8. Open inlet valve and run engine.

You will find this more effective than pushing a hose down the inlet as you gain generate more pressure.
If the water flow is still week, you need to check the raw water pump impellor, the heat exchanger matrix and finally the exhaust manifold. Both at the injection point and the exhaust hose junction as these two points will close up over time with deposits from the saltwater and exhaust gas.
You should check the exhaust manifold every two or three seasons. Failure to do so will result in low water flow or worse saltwater getting back to the exhaust outlet valves in the head. The latter will cause the valves to self destruct :-)

Best regards.

Ant.

Nigel · « **Reply #16 on:** July 07 2015, 14:28 »

Quote from: Impavidus on July 05 2015, 14:43

...
3. Push the end of your dingy inflator hose into the inlet side of the raw water filter ...

Surely a hosepipe would give better pressure than a dinghy pump? Or even a dingy pump

BillGiles · « **Reply #17 on:** July 07 2015, 22:41 »

Hum, putting one bar of incompressible water into a system designed for a gentle suction makes me wonder. And them maybe I'll give it a go!

Impavidus · « **Reply #18 on:** July 07 2015, 22:54 »

Nigel, yes you would think so.
But most Marina water supply systems go through filters and pumps to give clean and dependable supply in the UK. There are also back flow valves and a myriad of other gismos that reduce flow and pressure. All part of the regulation, red tape and health and safety culture; God bless them!!!!
My good lady wife bless her, works for a supplier of these black art things :-)

This results in an adequate flow rate, but very little pressure. To check simply put your finger over the end of the supply hose; distance will give you an indication of pressure. Nominally it will be about 2.5 to 3.5 bar.

A frightened, vigorous man (or woman) can get twice this pressure jumping on a dingy pump!

Best regards.

BillGiles · « **Reply #19 on:** July 07 2015, 23:18 »

For those who have not yet encountered it there are more and more marinas which do not supply hoses. When one enquires it is made clear that it is a 'Elf and Safety issue, Mate'. It seems that water sitting in a hose in the sunlight can be invaded by dangerous bugs and the marina might be liable. Like I have been in some of the grubbiest marinas with the tattiest of hoses and never been smitten with the least noxious growth.