I have never had a problem with my 60 4 stroke fuel injected motor untill recently. Someone may be able to confirm this, but don't run premium unleaded unless you have the right plugs (accidental fill up at servo). Runs way to hot. left plugs cooked and cost me 10% loss in compresion on no. 1 cylinder. At least that is what I dignosed a massive de-rate in power to be.

Dazza I've heard that too. A mate showed me an article saying to only run them on 91 octane fuel and defo no ethanol fuels.

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George, thank you for the extra info; I find it's always handy (even though I am obviously not a mechanic) to understand how & why different 'things' work - it's amazing how often you can apply it to totally different situations or circumstances.

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Ash
No worries mate, always happy to pass on info.

On the 91 fuel, the premium would not have caused your plugs to burn out. If anything it should have run smoother, more power, and clean as it runs. Burning plugs is from running lean. This would be due to the ECU. Depends if you have a closed loop or open loop ECU. Closed loop ECU's are a set program map and will not learn unless there is influence from an external source. An open loop will process data like knock sensors, lambar sensors, air temp, cylinder temp ect. and will deliver fuel accordingly. If one of your sensors isn't sending the correct signal then this can cause the computer to lean the mixture. Check if your motor has a sensor in the exhaust and one in the intake. Ensure these are clean.
Most motor manufactures say not to use PULP because it goes off much quicker than regular ULP. Couple this with the fact that most boats don't get used regularly they would be swamped with warrenty claims costing them a fortune to rectify.
And yes definatly don't use 10 %Eth fuel. The Eth absorbs water easily, but it will also seperate from fuel after a short period and then you have massive water contamination problems. And it also dosn't agree with most standard fuel lines. Eth fuel is a very well documented problem in the USA, due to their winterizing of boats through winter. Have a google and you will get more info.

Cheers

Gerorge, how can you tell if you have the open loop or closed loop program ECU?

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I've put ethanol in my boat twice before because of dodgy servos not listing it on the pump. A both times it ran like a bitch, up, down, and turning it self off. I went back to the servo the next day on my way to work and they blamed it on kids peeling off the stickers.

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Thanks for the info george i was worried there for a while when I read from one of the posts you should not use premium. That is all I ever use for 2 reasons.

Doesn't go off in the tank like all the other stuff (always leave tank full helps stop water build up)

More bang for your bucks

so if you always leave your tank full, is stale fuel ever a problem grumpy . If you do not use your boat a lot, or are you always topping it up after trips ??

Maxpower
generaly if you have a closed loop system your engine will be lacking sensors, as the injaction map is a set program so it dose not need the information. And open loop needs to monitor things to make sure that it's delivering the correct fuel/air ratio. these include an exhaust lamber sensor, a knock sensor (in the block) and air temp sensor (in the MAF or manifold). Generaly these three things will assist a computer in judging how much fuel to inject.
PULP starts to go bad after two weeks ( measurable in a lab) but you will really notice it at the three month mark when it's seized your high pressure fuel pump (this happened to me ) where normal ULP will still be ok at that time mark. If you do use it regularly an suspect it will sit for some time then invest in a decent fuel stabiliser. One that advertises stabeling fuel for storage or something like that (they are out there). The important thing is to put it in your tank before you fill, as the fuel you add will mix it for you, and fill to the brim. the less available air space the less water to condense or be absorbed.
Simply adding a shot of fresh fuel after every trip helps as well.
Don't be discouraged, I use PULP in my motors. The benifits far out weigh the negatives, just don't leave it sitting around with half a tank if you are going to leave it for sometime.

Ben I feel your pain mate, my wife filled the car with diesel at a palmerston servo, for nearly a month after her car was randomly stopping on the side of the road, the culprate was paper hand towel, the type at the servo. All we can think is that some little turd had rolled up some into the bouser spout of the diesel, and we were unlucky enough to get it.

I know there are a few people out there in the fuel industry, so if you read this and I have some facts wrong then please correct me. I don't know everything, contray to what I tell my wife.........

Know what you mean George..copped a bunch of cotton buds the same way..palmo servo as well. fuel up at c/linga now. No strainer sock on fuel pump inlet, s'pose it was a blessing in some ways...got to clean out the tank and replace fuel pump 350,000 plus kays on the origional, still tip a bottle of metho in the tank couple of times a year.

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Easy way to tell if you have a closed loop system it to check for a Lambda sensor in the exhaust system. The Lambda sensor gives the computer information on the oxygen in the exhaust and therefore how rich or lean the mixture is. This information is then used to dynamically adjust the map. The problem with the bulk of Lambda sensors is their operational range is quite narrow so if a mixture is radically rich or lean they won't be able to compensate dynamically but only incrementally, a common mod for some cars with the better more intuitive ECUs (Falcon EF and later) is to install a broad range lambda sensor typically lifted from a Porsche.
There closeth the loop.

I'd like to challenge the theory put forward by George on PULP as well but that is another story.