Another engine advice post

[Geoffs]

More advice please from those with more practical experience than myself. Those that know me know that I have a Mercruiser 30.L, that’s been giving me bother for the past year or so. 5 years old and done about 600 hours.

The latest thing, on returning to Rockley with Duncan a couple of weeks back. Horrible noise from water pump, and engine overheating. Had a look at thermostat, all bunged up with rust and crud. So removed ‘stat for run back to Poole, engine, of course, ran stone cold.

Fitted new thermostat, engine over heated without any load, squealing noises from water pump again. So, had new water pump fitted (engine circulating), impeller lose on shaft. Run up engine on no load, temperature holding fine. Took boat out and ran up power in Studland Bay, temperature rocketed up hard over on stop. So throttled back to let things cool down. When I checked the ‘stat, all blocked with rust and crud again, so removed it. Gave boat a good blast without ‘stat in, in the hope of flushing any rubbish out of everywhere.

So now have cleaned up ‘stat and checked opening temp., about 145 deg F (rated 140), and will refit on next visit. But, got a nasty feeling the thing will block up and overheat again.

Hope I’m wrong, but if not any thoughts from those in the know. Rust in ‘stat is quite large bluish flakes that wedge between seat and spring, thus preventing opening. Not what I’d expect from cast iron block & head. Only solution I can think of is to run without ‘stat, not ideal.


<hr width=100% size=1>Old Chinese proverb 'Man who sail boat into rice field, soon get into paddy'

 

[Wiggo]

possible to run the engine (to get the pump running) with an 'open' system? i.e. pump chucking rusty crud out of the top hose while mates pour in gallons of fresh from a bucket into the inlet side.

<hr width=100% size=1><A target="_blank" HREF=http://homepage.ntlworld.com/graham.wignall/boats/eulimene600x800.jpg>The old and the new</A>

 

[longjohnsilver]

Is it possible to back flush the whole engine by putting a hose on the outlet and hopefully then watching the rust flakes pouring out of the inlet.

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[David2452]

Sounds like a case for a muriatic acid soak to me, you will need to remove and block the inlet hose from the drive to prevent it draining out. Carefully introduce through thermostat opening, leave for about 3 hours then unblock the drive inlet hose and reconnect flush out with loads of fresh water. EXTREME care is needed so follow all usual precautions for working with acids. Muriatic acid is available from good plumbing shops and is sold as cast iron boiler descaler.

Hazards
· Muriatic or hydrochloric acid causes severe irritation or burns to skin and eyes. Vapours may irritate respiratory tract.
Handling
· Wear clothing that covers exposed skin areas. Use gauntlet-style acid-resistant gloves and eye protection when working with acid.
· Use only in well ventilated areas.
· Always add acid to water…never add water to acid.
· Do not mix muriatic acid with any other chemical


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[mercman]

This is a common problem on 3.0L. You will find it around the water pump housing. I would suggest you remove the drive and and split the upper and lower casing. Remove the impeller housing and the black plastic pipe that goes to the drive shaft housing and clean out. It is normally rust that builds up in the exhaust riser and is then blown out.The lumps either exit the transom side of the exhaust or fall into the drive housing in the drive. In the water pump is a by-pass hole that the crud can be drawn in to the water system and back into the thermostat housing. And hey presto stuck thermostat or buggered waterpump. Had 4 problems identical on brand new engines and numerous older models. Reworked cooling systems are now out on later models which seems to of eliminated probs. Hope this helps

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[Geoffs]

Thanks for the responses. Not sure about the acid treatment, though, sounds a bit agressive. Not sure how HCl will react with other materials in the cooling system, eg gaskets and bronze core plugs.

<hr width=100% size=1>Old Chinese proverb 'Man who sail boat into rice field, soon get into paddy'

 

[Geoffs]

Hmm, most interesting and useful, thanks for that.

Do you know if the reworked cooling system is available as a retro fit?

<hr width=100% size=1>Old Chinese proverb 'Man who sail boat into rice field, soon get into paddy'

 

[[2068]]

...or anything aluminium that might be in the block.

Tale of woe on the boatdiesel.com of someone who dipped their Volvo Penta heat exchanger (aluminium) in the acid for 30 mins.

Turns out, it should have been 30 seconds followed by a rinse in cold water. He now has a heat exchanger end piece with tubes from "Alien".

dv.

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[oldgit]

Re:Raw water disaster zone ....on old Mercruiser.

Frequently found the problem of scale caused my old mercruisers to overheat.Lost count of the number of times risers came off to dig out yet another load of rust and scale.Raw water cooling is complete and absolute rubbish.Fine for manufacturer and first user but warranty will be long gone afore subsequent owners get stiffed with an engine block rotting from the inside from day one.IMHO.

<hr width=100% size=1>If it aint broke fix it till it is.

 

[BarryH]

Re:Raw water disaster zone ....on old Mercruiser.

And the raw water pump in the leg, bugger all use if you need to change it while your out.

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[oldgit]

Re:Mercruisers aka Black Anchors.

Having had enough of the poxy thing decided to sell my Regal with the most unreliable ever raw water cooled mercruiser petrols.While out on demo with prospective buyers,riser clagged up again and pressure blew great big hole in rubber pipe.Steam and s***t everywhere......but they still bought the boat........good riddance to old...........etc etc.

<hr width=100% size=1>If it aint broke fix it till it is.

 

[mercman]

The cooling system would fit.It is a new style manifold and thermostat housing and various pipes to be honest its not worth it time you brought the parts you not far of a new engine.

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[Geoffs]

Re:Mercruisers aka Black Anchors.

Blimey, that's amazing that someone would buy under such circumstances.

With talk of 'red dreads', green 'Vilevo's' and now 'Black Anchors' on here, Hmmmm makes me wonder (in the words of Led Zepplin), if there is such a thing as a half decent marine engine. At least mine ran trouble free for the first 5 years/forums/images/icons/smile.gif

<hr width=100% size=1>Old Chinese proverb 'Man who sail boat into rice field, soon get into paddy'

 

[tico]

Re:Mercruisers aka Black Anchors.

Ah, but you havnt seen my two 'blue babies' unless you look at the gallery.

<hr width=100% size=1>Been there, done that, got the oily T shirt

 

[oldgit]

Re:Mercruisers aka Black Anchors.

Mine were nearly 20 years old and were really beyond saving,the entire thing I suspect was clogged solid.The horrid things would either
a.not start at all.
b.or not tick over
c. cut out for no good reason
d.die if any light rain within 100 miles
e or overheat at slightest provocation.
f all of the above at once
g the rams corroded like no tommorow
h.ohh and the thing liked to eat UJs for lunch.


<hr width=100% size=1>If it aint broke fix it till it is.

 

[Geoffs]

Re:Mercruisers aka Black Anchors.

Were they L4,s, V6's or V8's? Suppose 20 years ain't too bad for petrols, and have to agree raw water cooling ain't good news.

Mine is dry berthed (ie kept out of the water for 90% of the time) and flushed out with fresh water after every use (as per Mercruiser manual), only just had to replace anodes after 5 years. It starts well, runs well, ticks over fine, minimum clonk on engaging gear, pulls revs OK, just leaks oil and overheats.

I'm having to accept that I'm at the end of the trouble free period. Will be down in Poole this weekend to see if I can sort things out.

<hr width=100% size=1>Old Chinese proverb 'Man who sail boat into rice field, soon get into paddy'