Mariner 90hp Issue

[Jersey Sean]

Hello all, I'm new here and looking for some engine advice if possible please.
I have an old 3 cylinder 90hp Mariner 2 stroke, unsure of age as serial number is missing and has the wrong casing and cowling on it.
Two weeks ago after being laid up for a couple of years but recently serviced and run up for several hours on a hose we used it for a 34 mile round trip including about 12 mins at full throttle. Throughout the entire journey it ran very well, didn't miss a beat and started first time every time. While waiting on a mooring in the harbour for the trailer to arrive after our trip, the fuel ran out and the engine cut out. I topped it up with 5 litres of fuel (from the same batch it had run on all day - and tank was clean), primed the bulb and tried to start it again.
It wouldn't start without the idle lever up fully, misfiring badly, and refused to run below 1000 rpm on the idle lever without cutting out so was unable to put it in gear. When running normally it was ticking over at 750rpm with no idle.
Since then it's behaving slightly different, it smokes badly, misfires, it's very difficult to start, will occasionally run on tick over albeit with a misfire and requires idle to run continuously. The whole engine now seems covered in oil residue, although there's no obvious signs of leaks, with spark plugs removed it can be seen that the pistons have a build up of oily residue.
Oddly it seems to run better with the engine cover off and will cut out when it's replaced, and the sound deadening foam inside the engine cover is saturated in oil residue.

Before it ran out of fuel there was no obvious change in how it ran, certainly no sound or dip in performance to suggest a problem.

I've attached a few photos and a video of it running (just) yesterday.

Many thanks, Sean

 

[Bigplumbs]

I have had similar issues with a mariner 60 of the same design

My issue was a hole in the float of one of the carbs so the float filled so it was flooding and running like a dog to spot this you will see petrol coming out of the overflow on the card

These carbs are quite easy to remove and strip down

Also the gasket between the carb bowl and body can fail and let out petrol and let air in check this also

Hope this helps

Dennis

 

[Jersey Sean]

I have had similar issues with a mariner 60 of the same design

My issue was a hole in the float of one of the carbs so the float filled so it was flooding and running like a dog to spot this you will see petrol coming out of the overflow on the card

These carbs are quite easy to remove and strip down

Also the gasket between the carb bowl and body can fail and let out petrol and let air in check this also

Hope this helps

Dennis

Appreciate that Dennis, thank you. Will check k that out

 

[Fishtigua]

Yep, would go for 3 carb gasket kits, a fuel pump service kit and, as extra insurance, do the thermostat as well. The top cylinder can overheat if the stat isn't working correctly.

 

[Bigplumbs]

Yep, would go for 3 carb gasket kits, a fuel pump service kit and, as extra insurance, do the thermostat as well. The top cylinder can overheat if the stat isn't working correctly.

Find the problem first don’t do work just for the sake of it especially if you are on a budget

 

[julians]

If it was running perfectly and If it started to happen after you ran out of fuel i doubt it would be a failed float/leaky seal on the carb, its far too much of a coincidence that you ran out of fuel at exactly the same time as the carb seals/float failed.

Id be looking more closely at the fuel supply, possibly a blocked idle jet based on what you say about it not idling, it may be blocked with some debris sucked up from the dregs in the tank. start with just cleaning the carb jets fully and ensuring fuel tank is spotless clean.

 

[spannerman]

If it was running perfectly and If it started to happen after you ran out of fuel i doubt it would be a failed float/leaky seal on the carb, its far too much of a coincidence that you ran out of fuel at exactly the same time as the carb seals/float failed.

Id be looking more closely at the fuel supply, possibly a blocked idle jet based on what you say about it not idling, it may be blocked with some debris sucked up from the dregs in the tank. start with just cleaning the carb jets fully and ensuring fuel tank is spotless clean.

+++111

 

[Jersey Sean]

So this appears to have been part of the problem, along with a loose hose on the oil tank. New parts ordered, hoping this solves the issue.

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