Mariner 135hp two stroke issue

[smallribber]

Not so long ago we tested my friends new to him boat and used it for about 1 hour plus. He forgot to undo the vent on the plastic fuel tank. On return we noticed that the tank was crushed beyond recognition. We opened the vent and it slowly regained its shape.

While using the boat there was no noticeable effect on the engines performance. We were very surprised at this.

Yes check the vent but most likely the issue will not be that

[Yardstick]

Originally Posted by paintman

I wonder if the residual heat is vapourising the fuel at the engine - possibly in the pump or in the line - & the pump is unable to pull fuel from the tank until it's cooled down.
Something that used to happen on some Triumph cars which wouldn't restart after a fast run & then stop - much the same as your issue.
Some were Police cars which I would think would have been embarassing to say the least.

If it works on the Easy Start then it's fuel.
If it doesn't it might be something electrical again not liking the heat. Some Rover V8s had an issue with the ignition amplifier which saw Land Rover come up with a remote mounting.

Be interesting to know what happens!

ETA +1 for CDI's troubleshooting & another +1 for their speedy service when I needed a trigger & stator for my own 135hp.

I reckon you could be on to something here Paintman as the common denominator seems to be engine temperature. I don't get the issue on short runs only longer ones. Thinking about it, I've never actually tested the temperature sensor to see if it activates the buzzer.

[Yardstick]

Originally Posted by A1an

im not familiar with the 135, does it have an auto choke/enricher for cold starting?

Hi Alan, it's just manual choke.

[Yardstick]

Originally Posted by User name

While on the subject of checking the simple things, Is the tank vent functioning ok?

Originally Posted by smallribber

Not so long ago we tested my friends new to him boat and used it for about 1 hour plus. He forgot to undo the vent on the plastic fuel tank. On return we noticed that the tank was crushed beyond recognition. We opened the vent and it slowly regained its shape.

While using the boat there was no noticeable effect on the engines performance. We were very surprised at this.

Yes check the vent but most likely the issue will not be that

Cheers lads, the boat has an internal 90l tank and the vent hose looks to be in good order. The volume of fuel this thing drinks at wot is staggering so the vent is probably clear.

[paddlers]

I had one that gave every indication of a fuel issue , Clyde Outboards sorted it for me. Turned out to be electrical related to the coils as I recall . Ran like a sewing machine after their efforts.

[User name]

Originally Posted by Peter_C

I would imagine a tank vent not being open would cause the engine to stall while driving it and not restart. Speaking from experience...and it was an easy fix 30 seconds later after stalling as the tank was kinda shrunken.

Unless you get into modern emission standards and freezing conditions older boats with built in tanks do not have sealed fuel tanks.

My bad, I seem to have missed that the OP had an internal tank when I posted my previous comment.

Just for info sake re vented tanks though, it is actually possible to have these symptoms with a restriction in the vent.

A completely closed/blocked vent will eventually vacuum the tank and cut the engine like you describe, but a partial blockage or restriction can allow the engine to keep running while it's generating fuel pressure, but once cut out, the vacuumed tank draws fuel backwards until enough air gets through the restriction and/or back-fed through the carb itself. The primer will prevent backflow in equalised pressure situations, but a vacuum in the tank will get past it. That could take a while, depending on the restriction.

[Peter_C]

Originally Posted by Peter_C

Did you try setting the throttle to full throttle while cranking the engine? This causes a lean condition to help start a flooded engine, by removing the vacuum that would otherwise be pulling more fuel thru the jets. It can take 20+ seconds sometimes to clear a severe flood.

Yardstick can you answer this one question please? (I am still thinking flooded engine as ten minutes later it fires up, which is typical of a flood.)

[paintman]

Originally Posted by A1an

im not familiar with the 135, does it have an auto choke/enricher for cold starting?

On my own - which is an earlier one than the OP's - it's a manual enrichener & it requires the ignition key to be turned to the run position & pushed in to operate it.
You can hear a faint 'click' from it & extra fuel is allowed to go to the carbs.
Allowing the key to return to its out position closes it.

I normally only need it on the first start of the day & pumping the fuel line bulb until its hard & then a count to 12 after the opening click before closing it & cranking usually means first go starting

[Voodoo]

I was thinking about the coil packs getting overheated when the engine stopped due to heat soak and then being fine once cooled down a bit.

[Yardstick]

Originally Posted by Peter_C

Yardstick can you answer this one question please? (I am still thinking flooded engine as ten minutes later it fires up, which is typical of a flood.)

Hi Peter, sorry for the late reply. Spent yesterday servicing the trailer amongst a multitude of other stuff and today is just as manic.
Thinking back I probably didn't give it 20+ seconds of fast idle, probably closer to 15 max before firing up the back up engine.

[Yardstick]

Originally Posted by paddlers

I had one that gave every indication of a fuel issue , Clyde Outboards sorted it for me. Turned out to be electrical related to the coils as I recall . Ran like a sewing machine after their efforts.

Originally Posted by Voodoo

I was thinking about the coil packs getting overheated when the engine stopped due to heat soak and then being fine once cooled down a bit.

Cheers lads, that's another strong contender then. Seems to be a bit of a dark art this outboard stuff.

[Peter_C]

To keep the OP headed in the direction of fixing his issue, I am going to offer some insight. Keep the ideas coming though folks

Originally Posted by User name

~but a partial blockage or restriction can allow the engine to keep running while it's generating fuel pressure, but once cut out, the vacuumed tank draws fuel backwards until enough air gets through the restriction and/or back-fed through the carb itself. The primer will prevent backflow in equalised pressure situations, but a vacuum in the tank will get past it. That could take a while, depending on the restriction.

The fuel can not be sucked back out of the carbs once there is fuel in them. The fuel in the carbs is usually enough to run an engine for multiple minutes. Never say never, but this issue is most likely not related to fuel venting issues, unless there is a positive pressure causing the carbs to flood, which I highly doubt too.

Originally Posted by Voodoo

I was thinking about the coil packs getting overheated when the engine stopped due to heat soak and then being fine once cooled down a bit.

If there is more than one coil pack the chances of both failing at the exact same time would be extremely rare. If one coil works the engine will try to start and possibly start even running on half the cylinders. Outboards tend to run cooler then car engines externally, meaning you can touch an outboard vs a car engine that will straight up burn you. Coils fail often, but usually intermittently and randomly or just a straight up failure that never works again.

Another thing to try would be to run the engine flat out putting it into the possible failure condition, then let it idle for a minute and shut it down. If no failure it is one more piece of information to garner.

OP when you hold the throttle open do at least two burst of around 15 seconds of cranking with a short break between. If flooded it should start. Also use your nose to smell for fuel. Maybe even lift the leg out of the water while performing tests so you can smell for fuel, then if it starts shut it down immediately or lower the leg so as to not damage the impeller. As the impeller has a little water for lube you have a few seconds without causing damage.

[User name]

Originally Posted by Peter_C

To keep the OP headed in the direction of fixing his issue, I am going to offer some insight. Keep the ideas coming though folks

The fuel can not be sucked back out of the carbs once there is fuel in them. The fuel in the carbs is usually enough to run an engine for multiple minutes. Never say never, but this issue is most likely not related to fuel venting issues, unless there is a positive pressure causing the carbs to flood, which I highly doubt too.

It can be sucked out of the lines, and the fuel pump will struggle to match the vacuum of the tank.

I agree it's probably not due to the vent, hence why I suggested EasyStart first, but all basic checks should be done.

[Yardstick]

So, as an update we're a week into our holiday just outside Oban and the boat has been in daily use running for several hours each day. So far the engine has been fine and has restarted every time, that said we've another week to go so I hope I'm not tempting fate by saying it's ok. The fuel bill is not ok though

[Pikey Dave]

Enjoy the water, forget about the fuel bill. Make sure you visit the Green Shed in Oban for the best crab sandwich ever.

[willk]

Originally Posted by Yardstick

The fuel bill is not ok though

Yeah, but the more fuel you burn, the lower your annual cost per hour operating.

Gerrup!

[Pikey Dave]

Originally Posted by willk

Yeah, but the more fuel you burn, the lower your annual cost per hour operating.

Gerrup!

impeccable man-maths

[Yardstick]

Cheers lads. We're on first name terms with the petrol station attendant now🤣

[A1an]

Originally Posted by Yardstick

So, as an update we're a week into our holiday just outside Oban and the boat has been in daily use running for several hours each day. So far the engine has been fine and has restarted every time, that said we've another week to go so I hope I'm not tempting fate by saying it's ok. The fuel bill is not ok though

I hope your problem has sorted itself.

I’d hate to think of the money I’ve spent on fuel over the years.

[paintman]

Originally Posted by Yardstick

The fuel bill is not ok though

They're not the most frugal of engines!
But on the plus side it shows that the weather was good enough to get maximum use