Fuel Mix

[sunnycoast62]

I have a Mariner 30hp on a NOMAD 4.29 Stacer which I purchased Nov 2007 and has about 15hrs......... I have just had it's first service and have been told that the fuel mix is to rich, yet I have added the 50:1 ratio since the initial two 1/2 tanks (Underfloor 50ltr tank) of 40:1 as per spec's and instructions. My question is, going by the specifications of the fuel mix of 50:1 how does the mix end up rich...... Confused!!

[Outsider1]

I have a Mariner 30hp on a NOMAD 4.29 Stacer which I purchased Nov 2007 and has about 15hrs......... I have just had it's first service and have been told that the fuel mix is to rich, yet I have added the 50:1 ratio since the initial two 1/2 tanks (Underfloor 50ltr tank) of 40:1 as per spec's and instructions. My question is, going by the specifications of the fuel mix of 50:1 how does the mix end up rich...... Confused!!

Just a hunch, but what is your mix to achieve 50:1? ie ml of oil to litres of fuel?

Dave

[sunnycoast62]

Thanks for the reply,
If I put 25 lts in the tank then I would add 500ml of oil.

[cormorant]

G'day.

Too Rich usually refers to too much petrol oil mix going through the carby and resulting in a motor that smells a little petrolly (sic) and is blowing a bit of smoke. Too rich means too much fuel going in to be combusted and will mean the mechanic needs to adjust the mixture screws. Too rich a mix will "wet " plugs and cause carbon deposits in cylinders on the plugs and will gum up rings. all these will shorten the life and reliability of your motor. It may have been run rich with too much oil in the run in period.

Motors can seem to be too rich if the plugs fitted are the wrong temperature and the motor spends extended time at idle or low speed and doesn't get a good high spped run for about 20 minutes every day out. Don't spend forever flushing small outboards on idle a few minutes is enough.

Stale - old fuel can leave deposits that look like a rich motor as it has more oil components than volatile components - only use fresh non ethanol fuel.

First thing I would do- ask your mechanic to explain what was wrong and what he did about it and what he wants you to do about it.

Second I would make sure you mix Fresh fuel exactly and accurately as per the manufacturer says into a clean tank.

I would change to a full or semisynthetic quality oil as it will smell less , leave less ash and be better for your motor long term and won't add much to your boating cost.

If it was really rich I would ask the mechanic to use a product like power tuner and clean the combustion chamber with it and put new plugs in. This product sprayed down the carby throats with the motor running cleans out all the crap. Best done just before you are going out on a days boating so your motor gets a good run afterwards.

Let us know what you find out as lots of people like mechanics use the words "rich" in a number of contexts to describe a number of situations. Ask him what he meant and the people here will tell you whether he is full of it or just dumbing it down for you or whatever.

Happy boating.

Corm

PS do you premix some oil and fuel in a jerry or just stick the oil in the tank and fill up?

PSS- I don't know mariners - your motor isn't oil injected is it ?

[Outsider1]

Thanks for the reply,
If I put 25 lts in the tank then I would add 500ml of oil.

Good, surprising how many think it is 50 ml to the litre.

Read cormorant's post, I think he has hit the nail on the head.

Cheers

Dave

[sunnycoast62]

Hey thanks guys!!! your info confirmed my thoughts of probably stale fuel as being the culprut in this case...... you just never know!! that is why I asked the question..................... Just so you know it's a Mariner and they have just added a 3 + 2 year extened warranty on the motor from Mercury so I don't want to do anything wrong that might void it. As I have had almost a full tank of fuel just after Xmas I assumed that stale fuel might have caused this. All of your comments are much appreciated and gladly taken on board.

Warren