HELP, engine hot but not ???

[Paul Craft]

After my last trip out of around 1 hour, taking it steady, 10 knots max,
High temp alarm sounding, but temp was normal, oil pressure and battery gauges dropped,
but on opening engine hatch, expansion tank was empty and coolant fluid over engine bay, why ???

[seapuppy]

first ..welcome to the zoo....as I'm not there I can't tell you what it is...your going to have to do some detective work...if the engine was truly hot...the expansion tank might have had more coolant in it....so...if it was all over the engine bay..that means a hose or something let loose....the other things that can trigger the helm alarm is low drive fluid...and low oil pressure..since you said it was ok...check the oil to see if there is coolant in the engine oil....also look at the end caps for the heat exchanger...

SP

[shrew]

Hi Paul Craft, welcome aboard.

Seems like an odd combination of problems. If the Antifreeze resevoir was empty and coolant all over teh bilge, then that would certainly lead me to believe you were overheating. Keeping in mind that the raw water is drawn in and run through the heat exchanger and manifolds and risers. Typically blockages anywhere in teh system, could lead to overheating. However, since the heat exchanger cools the antifreeze with the raw water, AND the Antifreeze resevoir was empty, then no matter how much raw water if being drawn in, if there is no AF to cool, there is no way to cool the block. However, I would expect the high temp alarm to corrospond to the water temp guage. The first thing I'd be looking at is if you have a leak in the coolant hoses.

Oil Pressure and voltage also dropping?? The bilge wasn't filled with oil, was it?

[pascavone]

sounds like you fan belt came off.

[Paul Craft]

Well upto now, I have found the Thermostat had come loose, so the Temp reading was in the engine bay not the engine, replaced this but still the same problem, my marina is looking at it closer, will let you know when we know, thanks.

[Timski]

I have a similar issue after running about an hour - helm alarm goes off but all the gauges look ok. Have never found the issue but expect its a bad sensor I'd be interested to hear what you find.

[Paul Craft]

Just got the Invoice from my marina, it took them 8 hours to find that it was a weeping "o" ring, that caused a loss of pressure and so the expansion tank to empty,
£2 for the "o" ring £29 for Volvo antifreeze and £400 labour, they tell me they had to re-pressure the system and clean the bilge of old antifreeze, feel robbed but what can I do???

[pascavone]

i don't believe it....

sounds like they tighten a hose clamp.... and billed the rest.

[Huddo007]

I am addding my experience to this thread as I hope it might help someone else as the title is very fitting and may search the thread, I had an over heating problem alarm that i could not find nor fix for a very long time, I will add that NO mechanic ever did find the problem it was by pure chance, it was all over the place sometimes it would alarm and other times not, it always seemed to alarm during a night cruises but sometimes during the day, the temp gauge would slighly rise and the alarm would sound, It was on the 350 ci (250hp) Carb merc, I changed thermistats, risers, manifolds leg impellor the works, turned out that the NAV lights were giving the TEMP gauge some feedback and causing a false alarm, sometimes the NAV lights would get switched on during the day (by accident) and that caused the daytime fault alarm but showed why it predominantly happened at night.

[cj]

Hey there.....a temp gauge will only work if there is coolant &/or water in the system. If you blow/boil all of your coolant out of the system there will only be air left and the temp gauge will read normal, when in fact you are overheated. Check the pump impeller, thermostat, and manifold and risers, etc...etc.....and of course the hoses & clamps.....touch the top of the risers and you will know if it is a false reading or not...lol.......bottom line....if there is coolant in the bilge then u have a leak or it has overheated and blown everything out the reservoir.
Cheers
goodluck

[lifespan]

1999 maxum 2100 SC. Just replaced exhaust manifolds and riser elbows. Took to Lake this morning and in neutral and idle, engine started to cut out like starved of fuel. It shut off and I started to get a continuous alarm. Started boat again without issue and seemed fine. Alarm went away. Temp gauge, oil gauge perfect. Well oil about 50-55. Got back to dock and shutoff and restarted a few times, no idle issue, no alarm. Out drive oil full. Any ideas what alarm is?

[mmwjr]

No OP once engine died

You need to keep this to one post instead of post in multiple threads, makes it hard to follow and give help.

[lifespan]

No reply in other so searched where this topic was already posted. Apologies