Advice-outboard slowly conks out- any budding mechanics!

[mortyb]

I have a 25 mariner 2001 model 2 stroke which has been going great until the last year. It starts well, I run it nearly full for about 15 to 20 mins to my fishing spot. It idles then, stop and start for about 15 mins while I chase bait. Then run out pots for about 30 mins, some idling and some running to the next spot. Not a problem. Then anchor up for the tide eg run out or run in. After a time, start the motor to go check the pots. Usually starts fine but sometimes a bit rough idling. Go check the pots and while idling the revs start to drop over about 30 seconds until it conks out. Then takes quite a few pulls to start. When it starts it is a bit rough and appears to be very smokey. I have to go for a quick run to get it going well. Then when I start to idle again to check the pots it starts to lose revs again etc. To compensate to keep the revs high I pull the choke out a way. The next morning etc to flush the motor it starts fine and idles well. I mix 50 to one as per manual. I have taken my motor to the service man a few times but he says it runs fine for him (running in the tub). Spark plugs changed during regular service. Any suggestions?

My thoughts 1. crap oil. I use valvoline. 2. crap service man. He said I will have to take him out for a run to show him what acutally happens. 3. Since I only go out about once a month/6 weeks and the fuel evaporates. When I go out again I top it up to full and add the required oil. (I don't like being short of petrol) But the evaporated petrol leaves a concentrated oil level (?)and therefore topping it up and adding oil means there is to much oil and then oiling up the plugs after I run it hard and then idle.

[PROS]

Check/clean carburettor?
If you have a water/fuel separator/filter, check & renew, they get rusty and cause similar issues.

Few basic suggestions to start with

MAx

[JEWIENEWIE]

I would not have any real idea but when i was new to boating, I had similar issues, turned out my breather was blocked in the tank and couldn't keep up, when she stalled, it caught up and would start and run ok until it ran out of air again...........
JN

[stevebris]

Get a better marine mechanic who will do a water test.

[Willdoe]

You may have crap in your fuel tank blocking the suction filter. I drain my tanks regularly using an inline filter in the siphon line to make sure I have no crap or water in it. Drain yours, you can always put into your car if it's filtered.
Take the suction line out of the tank and check for blockages.
Also check your fuel line connections you may have one that partially disconnects with movement.

[Moonlighter]

Unlikely to be anything to do with the oil. Nothing wrong with Valvoline, in fact, Tohatsu recommended it for their direct injected 2 strokes, they had it tested in Japan and it got the tick from the factory! Ran it in mine for 5 years.

As others have said, make sure the breather on the fuel tank is open so air can get through.

Sounds like it needs a good clean out, carbs cleaned and a tune up. Set of plugs. Possibly jets are blocked with dirt, it certainly sounds like it is starving since you say it goes better when you hit the choke.

There are some good mobile mechanics around that should be able to diagnose and fix that for you. Give Glen a call at Mobile Outboard services 0402 456 738 (tel:0402 456 738). Good Guy and great prices, he might come out that way, you can ask anyway.

The Other thing is to fit a good water separating fuel filter in the fuel line between tank and engine. No engine likes dirty fuel, and it is easy to pick up a load of crappy fuel from garages these days.

[scottar]

It almost sounds like it is overfueling slightly or running rich. It isn't starving as it will run at revs ok. Have you ever pulled a plug when it's playing up to see if they are wet with excess fuel. Possible that the adjustments are out or needle/seat assembly isn't playing the game properly for whatever reason. As already suggested a good inspection/clean of the carby's and a tune up for starters. As Moonlighter has said - nothing wrong with Valvoline two stroke oil. I ran it in a 40 Horse Evinrude for over 15 years without issue and still use it in my Merc-hatsu.

[mortyb]

Thanks everyone. I am confident it is not a breather/starved of air problem as raised by some above. ie runs well for quite a while, but then plays up. The mechanic I have taken it to advised that he did do a 'clean' of the carby when I took it in one time with this problem. Although crap in the system and playing up jets does sound like a possibility. Scottar, I have taken the plugs out and they seamed oiled up/wet which is why I thought it might be too much oil in the system due to evaporation. But this was after it conked out and I was trying to start it for a while. I think I will filter my tank of fuel (to remove crap) and also take it to a new mechanic (or moonlighters suggestion) for another opinion.

[Willdoe]

Why not put the old fuel in anothet container ar borrow another tank and start with fresh fuel.

[Fed]

Sounds like a cold motor to me.

After a time, start the motor to go check the pots. Usually starts fine but sometimes a bit rough idling. Go check the pots and while idling the revs start to drop over about 30 seconds until it conks out. Then takes quite a few pulls to start. When it starts it is a bit rough and appears to be very smokey. I have to go for a quick run to get it going well. Then when I start to idle again to check the pots it starts to lose revs again etc. To compensate to keep the revs high I pull the choke out a way.
At this point are you starting it as a stone cold motor with choke & fast idle then allowing it to warm up & settle down before moving off?

[Moffy]

Fuel pump.....

[littlejim]

I'm with Willdoe. Sounds like crap sucking on to tank filter after a decent run.
look for kinks in fuel lines too. Eliminate the simple/cheap causes first.

[Spin]

Fred what you drinking where do we get some

[Fed]

Fred what you drinking where do we get some
Was that for me Spin? What do you think the problem is?

Moving right along...
Any motor that can run at near WOT for 20 Minutes doesn't have a fuel delivery problem so you can forget blocked vents, crap in tanks & faulty fuel pumps.


It starts well, I run it nearly full for about 15 to 20 mins to my fishing spot. It idles then, stop and start for about 15 mins while I chase bait. Then run out pots for about 30 mins, some idling and some running to the next spot. Not a problem.
Morty I bet if you switched off at this point for 5 Minutes and then restarted it would run perfectly but leave it off for more than 30 Minutes and it's heading into the cold start zone. Outboards cool very quickly with half their mass in the water.

[tunaticer]

If your plugs are coming out oiled cheange them for the correct heat range surface gap plugs.
I suspect you are choking again for the restart?? Your choke system is a throat butterfly or a fuel dosing syringe type?
If it is a syringe type you could be over fueling on the restart causing a domino affect with over-oiled fuel.

I was advised by the Evinrude salesman / mechanic to run my 25 rude on 75:1 not 50:1.......that was 20 yrs ago this October and it has not missed a beat in the many many thousands of hours it has run. Engine mounts and impellors and two, yes two sets of plugs in 20 yrs. I'm not complaining about his recommendation.

I run two 25 litre tanks and run it dry before switching tanks always. That way I know the mixtures are good.

[mortyb]

Thanks everyone for the comments. Took the motor in for a second opinion and hopefully to get it sorted. It turns out it is fuel related, but a mechanical problem. A primer spring in the carby is supposed to push and hold a ball bearing, to stop petrol flowing in with the ball bearing. The ball bearing was slipping inside the spring (they did not know why and had not come across it before) so not sealing, therefore letting extra fuel into the carby. It could handle to fuel at higher revs (which was the case when motoring to my fishing spot) but when lower reves/idle it would flood, hence the slowly conking out. The mechanic also said the motor was tuned for high revs at idle, which was probably to compensate for the rough running at idle with the extra fuel. The also changed the plugs. Anyway, got it back friday so hopefully I can take it for a run in the Logan before the full moon to see if it is fixed.

[Moonlighter]

Thanks for reporting back. It is always good to do that, as apart from anything else it may help other people with simlar problems.

[Fed]

If it all works your mechanic sounds like a keeper.
Is that spring inside a remote enrichment valve, I thought you had choke plates from your first post?

To compensate to keep the revs high I pull the choke out a way.
Sounds like something you could spend years trying to find, great result.

[Darren J]

I was advised by the Evinrude salesman / mechanic to run my 25 rude on 75:1 not 50:1.......

I would agree with this, after running 50:1 for some time premix with a V4 140 Evinrude I was advised the same from a very reputable mechanic that I had known 20 years earlier (he was a marine mechanic then as well).
Swears 75:1 for premix.

[ericcs]

not sure about all of the older omc 2 strokes, but my old 80's 30hp had a 100.1 sticker next to the fuel connection. this was for the USA emissons law. so it appears they can run even leaner.