what have you sucked up (your raw water intakes!!)

stefan_r

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I am a bit concerned about sucking a bag or something up my raw water intakes into the cooling system and blocking it, overheating the engines and probably providing me with the sort of bill I can frame and show my grandchildren...

At SBS I say a gizmo on the Halyard stand that was an exhaust temp sensor and was sorely tempted as it did seem like a good idea but it will probably work out to be a £500 or £600 investment.

Already got ropecutters, seen 2 knot drop in top end and not sure how much change in fuel efficiency....is this just another bit of kit for the paranoid or a worthy investment???

Spoke to my insurers and they said 'oh yeah mate if it is an accident then you're covered for engine repairs'...nothing explicit in the policy handbook and - as I work in insurance - I know that if there is a way to avoid paying, they will.

Cheers
Stefan

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claymore

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I was at Ardentrive, Kerrera this summer when someone got a jellyfish sucked in. They were just checking that the exhaust was spitting out water after starting the engine. Noticing that it wasn't the problem was soon discovered. It's doubtful whether an exhaust temperature monitor would register this kind of problem soon enough. I have a skin fitting over my cooling water intake which should stop something big, but a plastic bag sucked on whilst the boat is stationary would be hard to discover. No substitutes really for looking over the back and seeing a health splash of cycled water being spat out and if motoring, keeping an ear on things.
 

ChrisP

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Had to change an exhaust last week. After fitting the new one it seemed to run hot. Yep you guessed it. A bag partially blocking the intake. strange thing is the engine ran fine at all revs but I'm sure it helped damage the rubber hose.
I'm thinking of fitting a couple of thermo-couples or RTD's to the injection bend and hooking them up to a small mV meter. Even without calibrating them it will give an indication of a problem when the needle moves from the normal running position. Alternativly a pair of motor thermistors linked into an alarm would do the trick. Total cost in either case will be less than £20.
 
G

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Re: sucking up

I have heard this happening, but not lots. Depends if you are in cleanish sea or scummier rivers/estuaries I spose. I used to have ropeciutters but ditched them for noticeable speed improvement. I did once have an overheated engine due to brainless nit (me) checking filters and forgetting to re-open primary seacock - alarm sounded. Doesn't yr engine have an alarm at all? Obv a good idea to have temp guage and overheat alarm as minimum. Also as others have said check exhaust outlets are splooshing after startup each time.
 

jfm

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Re: measure vacuum not temparature

In practice in the Solent we never pick anything up. Only clean the filters at the annual service.

Re the exhaust heat sensors, as others have said you could lash something up from Radio Spares/Maplin. But really these aren't the best approach, they only tell you too late when the engine is pretty hot. The best kit is vacuum sensor switches on the raw water intake downstream of the filters. These trigger by sensing the pressure drop when the filter is blocked up while the pump is still spinning. Quite easy to fit, my father did it diy on his boat. Better yachts have em as standard, the lowest grade Uk boat I have seen with them is the Sealine T51 where they're standard (see MBM back issue 2 years ago). If you are doing it diy this is the way to go, not crummy heat sensors.

Matts you should specify them on Leopard though I suspect they'd be insulted as they will have thought of them already

JFM
 

hlb

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I had two engines overheat last year and felt a right prat getting a tow back by the defence Police. Engines started fine after that, Must have been a lump of carpet or whatever stuck under the inlets. But the buzzers came on so no real problem exept I was on my own and drifting up the rocks at the time. course the polic boat was doing a good 3 knots at the time comming to rescue me. Arnt our policmen wonderfull!!

Haydn
 

ArthurWood

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We have a lot of sea grass floating on the ICW in Florida, especially after a storm. I once made the mistake of ploughing through a reather dense clump and both engines immediately overheated. The alarms screeched, I stopped, gave a quick burst in reverse and both intakes cleared. I've since found this to be a good method of clearing stuff stuck over the intakes. It wouldn't help if the stuff had actually entered the hose, of course. For that I have Thoroughflush fittings on my strainers which allow me to fit a hose and back flush.
 
G

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Tel tales

Heres a cheap alternative to all that electronic stuff !!!!
A small pipe (3/8") taking raw water from just before the water injection elbow into the exhaust, to a small skin fitting on the top sides. And thus a constant indication of raw water flow. Very handy if you have exhaust boots or outdrives.
Most Yanmars have an alarm in the raw water curcuit which is instant. But are not a standard part of the wireing loom or panel in the UK.
 

jfm

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Tel tales - great but where to fit?

Jolly good idea, same technology as used on outboards last 50 years, works well.

But you have to locate the skin fitting where water spout is visible. On outboards it points down usually but racy type fit nozzles so the plume goes skywards. On a large powerboat it must be clear of the waterline (else you will never see the spout due to spray) but topsides would be antisocial for the poor people on the pontoon helping you with lines, as you come in and spray them with a 3/8 jet. Where have you fitted yours? What about on the bathing platform pointing upwards so it looks like a massive Yamy Jetbike at high speed, or point it 45degrees backwards so it looks like you have Arnesons (you might need to have 3inch dia not 3/8th to look more convincing, and in that case go easy on throttle blips when mooring stern to)

JFM
 
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Deleted User YDKXO

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The problem nobody's mentioned is fire. I believe MBY's Princess 360 caught fire (in Cowes, I believe, during a recent Powerboat Festival - bit embarassing, really) when a cooling problem caused an engine overheat on one of their Perkins Sabre engines resulting in an exhaust hose fire. After that they fitted these Halyard exhaust temp. sensors which they reckon would have given them an earlier warning
My own boat had them fitted from new; the sensors themselves are located under an exhaust rubber hose connection and I certainly believe they give a far better indication of engine overheat than the cooling water temp guages.
A good investment? I guess MBY think so but most boats dont have 'em and you dont hear about boats going up in flames that often, do you? Its a bit like a liferaft. You hope you never have to use it.
 

jfm

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Re: no!

Stefan if you want really early warning get vacuum switches as mentioned above and as fitted on Sealine T boats. This will give you warning much sooner than Halyard stuff

JFM
 
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