Mariner 15 HP Four Stroke Issues

smallribber · 31 March 2017, 06:54

On my 3.4 m rib. I have a nice 15 hp 4 stroke Mariner outboard that performed flawlessly last year. This year it has now let me down on 2 occasions.

First occasion was all started well but after about 15 mins running it would only run at tickover. Took it home stripped the carb and it went fine. So I took it out today for a long blast up the river and it went a dream for about 2 hrs then I throttled back and this time it would not run a low speed. Got a tow back so all was ok.

I am thinking I have shite in my fuel so I will clean out the whole system and clean the carb again.

I was wondering if anyone else has had similar

Dennis

Fenlander · 31 March 2017, 08:53

Dirt in the fuel system is the simplest to resolve so I hope it's that, did you find any dirt though? If you think it's the issue after cleaning everything I'd fit an additional clear canister fuel filter in the fuel line where you can see it easily.

There was discussion on here a while back that aged Mariner fuel lines can collapse internally and intermittently cause fuel starvation, this could be happening with any part or any make of fuel line or the primer bulb so that needs checking. The tank pickup needs pulling out to check for debris and that its tight with no faults. For example I've seen an OE tank on a Mariner where the pickup pipe was too long from new and as it aged it kinked massively reducing flow. Also seen Mariner tanks where the pickup comes loose from its connection at the top to the underside of the connector block, this can draw air or fall off completely. I always check these tanks and add a pipe clip to be sure.

If the fuel line is 100% and it keeps happening perhaps think about the fuel pump. Also maybe the carb needs a pro ultrasonic clean due to gunking up with modern fuel deposits.

Beyond that I've experienced ign components faulting erratically due to heat soak but that's far more rare than a "simple" fuel issue.

spartacus · 31 March 2017, 09:08

Has the outboard been serviced recently?

Sounds like fuel issue, but could be anything. Assuming you have a 25 litre fuel tank, check the contents. If you can decant into a jerry can and use fresh fuel, then you can rule out contaminants. You can use the petrol in a mower! Also consider fitting a water separating filter before fuel goes to the engine if you don't already have one fitted.

Check the fuel filter on the engine. Also check the rubber hose on the tank and primer bulb. If the primer bulb rubber feels overly hard, then replace. The diaphragm can deteriorate. Quicksilver offer good replacements. Check the actual connection to the engine too. I had my Tohatsu engine fail here as the after-market fuel connector 'o' ring was dislodged.

Did you alter any of the carb settings when you dismantled such as the fuel air screw?

Lastly, the spark plugs. Pull them and have a look. Are they wet or oiled up? Should be lightly dusted and clean. If in doubt, replace with correct specification plugs.

smallribber · 31 March 2017, 10:46

Thanks for your comments.

I have new plugs already and will clean and check all the things you suggest. I am very certain it is crud in the fuel as when I removed the filter I could feel some rough deposits in my hand but not easy to see. I have a new filter now and will set to work when the rain stops.

I notice also you can buy an ultrasonic cleaner on ebay for about £40 so might be worth a go

Dennis

smallribber · 31 March 2017, 17:32

Well this is what I have done today:

Taken out all of the petrol
Removed the tank and cleaned out (But it was actually very clean)
Dip pipe filter is clean
Petrol pumped out well via the bulb
Removed and stripped down the carb
Sprayed and cleaned inside of carb
Poked through all jets with fine wire and sprayed carb cleaner all over
Cleaned out any small bits that were about (Actually hardly any)
Filled with new 95 octane petrol
I also upped the idle speed a little

She now runs on slow very well and as much as you can do in a tub runs at fast speed.

I can only now try her out on the water.

Pity I don't seem to have space for my little 3 hp 2 stroke as a back up when I do the tests

Dennis

Fenlander · 31 March 2017, 17:42

Hope it goes OK now Dennis. As a matter of interest what is the fuel filter on that engine... a plastic canister type under the hood where you can see the contents?

beerbelly · 31 March 2017, 18:11

Quote:

Originally Posted by Bigplumbs

Thanks for your comments.

I have new plugs already and will clean and check all the things you suggest. I am very certain it is crud in the fuel as when I removed the filter I could feel some rough deposits in my hand but not easy to see. I have a new filter now and will set to work when the rain stops.

I notice also you can buy an ultrasonic cleaner on ebay for about £40 so might be worth a go

Dennis

what is this rain you speak of nothing but sunshine in the north east

hope you get it sorted sounds like a fuel issue tiny est bit of crap can cause huge problems

smallribber · 31 March 2017, 18:24

Quote:

Originally Posted by Fenlander

Hope it goes OK now Dennis. As a matter of interest what is the fuel filter on that engine... a plastic canister type under the hood where you can see the contents?

It is a plastic can type one under the hood but it is opaque so cant see nowt which is a pity

Dennis

Poly · 31 March 2017, 19:25

Quote:

Originally Posted by Bigplumbs

Pity I don't seem to have space for my little 3 hp 2 stroke as a back up when I do the tests

I share your pain - but my engine is bolted in place. Is there really no room to carry it up front and if needed shift the main across and squeeze the Aux beside it? Or work out a bracket arangement?

Fenlander · 31 March 2017, 20:51

>>> it is opaque so cant see nowt which is a pity

Then I really would get an inline one where you can see if there is debris buildup... they are so cheap and easy to splice in the fuel line.

smallribber · 31 March 2017, 21:41

I am going to carefully cut my old filter open to see if there is any crud in it.

A clear one would be lovely but there is very little space under the hood.

Fenlander · 31 March 2017, 21:50

I really meant cut the fuel line somewhere you can see it... or is it all hidden in the console/ducting?

smallribber · 01 April 2017, 07:47

Quote:

Originally Posted by Fenlander

I really meant cut the fuel line somewhere you can see it... or is it all hidden in the console/ducting?

A lot of it is hidden and it would be difficult to put suck a filter somewhere where it were not vulnerable

Fenlander · 01 April 2017, 09:48

Ahh OK... I was thinking of this with my SIB head on where you see the whole fuel line. Even so if I were running a RIB however small I'd have a filter like this or similar on the transom...

http://www.ebay.co.uk/itm/OUTBOARD-M...EAAMXQ1d1TIvwu

I wanted to put one on my current setup when I bought the Suzuki new last year but it was too much faff to know how to mount it with a daily inflate arrangement... still thinking of an extra small inline though.

Perhaps like this... http://www.ebay.co.uk/itm/Boat-Marin...UurVhOrnk_-axA