Dolphin Engine Overheating

MarkCX

MarkCX

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My 16hp Dolphin 2 stroke petrol inboard has started misbehaving. The last couple of times I’ve tried to go out, the engine temperature alarm has started sounding. I’ve no idea what temperature it’s meant to go off, or what’s causing it to overheat. I’ve replaced the pump belt - it seemed a little worn, checked the impeller which seems fine, and made sure none of the pipes are blocked as much as I can. There’s definitely water coming in through the seacock and definitely water coming out of the wet exhaust. Any suggestions? (Other than get rid of it and stick an outboard on the back ?)
 
How hot is the water coming out of the exhaust?

If it's the same volume as usual and the same temp as usual, it's more likely to be something wrong with the temp sensor although without further knowledge of the cooling system on the Dolphin one can't be sure.

Richard
 
I would get one of the covid temperature tester to measure the actual temperature of the engine.

As its raw water cooled if its somewhere 70 degrees C that would be OK but if its getting to 90 + C you need to look further
 
Had a go with an infrared temperature thingy. Just idling the cylinder head settles at about 40°C when warmed up, but when running in gear with a reasonable amount of throttle it is reaching about 95°C, so I reckon the sensor is ok. It’s the first time the alarm has sounded in the dozen years I’ve had the boat! Difficult to tell if there’s significantly less water from the exhaust. It seems to be a similar amount as before, but it’s been a while what with lockdown etc.
 
I'm not familiar with the engine at all, but maybe a failed thermostat?

You can test them by heating in a saucepan of water on the stove - at the specified temperature you should see the valve part visibly move.

(To be clear, it doesn't move in one sudden jerk when the temperature is reached. It'll move fairly slowly, but the difference between "open" and "closed" should be easily visible.)

Pete
 
+1 to what Pete says about a thermostat.

They are usually marked with the temperature at which it should just start to open and maybe also with the temperature at which it should be fully open.
 
I know Op said pipes are clear BUT-does the raw water pump into the hotest part of the exhaust system at some point in the same way as a Volvo? If so this can cause carbon build up & blockage. So although one might think it is clear it creates back pressure on the water release.
 
Well. That wasn't very difficult Dolphin Engines - British made marine auxiliary two stroke engine for leisure and racing yachts

Ask the makers.

Have you checked your anodes? https://www.dolphinengines.co.uk/docs/PBO_ARTICLE.pdf


Screenshot-2021-04-03-at-09-42-45.png
 
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Just checked anode, seems ok.

Read the PDF already, but nothing to really help.

Asking here because Dolphin Engines (the company) seem to be only ticking over and I haven’t got replies to other queries. Things were very different a few years ago and there was always someone on hand who could help.
 
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From Caraway's link you may need to check the water passages.
1617440257928.png
Even for a non mechanic it should be easy to take the cylinder head off and check the passages. Vintage motorcycle enthusiasts used to do this by the roadside.
 
Where is the temp alarm, what is it attached to? If there's no thermostat on these things and there's water coming out of the exhaust it's likely giving you a false alarm.
 
MarkCX said:
The engine was rebuilt last year so I suspect not much has changed .
Click to expand...
Possible excess of Hermetite or dislodged rust/ calcium/ muck forming a blockage?
I always think it's best to check the last improvemrnt or repair, so often this results in further problems.
 
The sensor is attached to the cylinder head. The IR reading I took when it was sounding was about 95°C - tricky to do in a narrow channel trying to get back to my mooring. A bit higher than the 80°C quoted in docs above.
 
andsarkit said:
From Caraway's link you may need to check the water passages.
View attachment 112736
Even for a non mechanic it should be easy to take the cylinder head off and check the passages. Vintage motorcycle enthusiasts used to do this by the roadside.
Click to expand...
Could you help, I live in Sydney and need to buy a Dolphin 2 cylinder marine motor head gasket any ideas where to get one As the motor ceased production years ago and I can't find anyone with spares or a diagrAm to make a new one
 
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