Motor Problem Update

[locodave]

So i managed to look into the motor today with my mate and we did the following.

• Check fuel lines
  
• Check spark plugs
  
• Check compression
  
• Open up carbys and clean them out.
  

Everything was in working order. I cleaned the spark plugs, they were dirty but no biggie.

Compression test came out really good. All cylinders hold close readings.

Carbys were like new on the inside, everything in working order.

So what could be next? I'm thinking fuel pump and fuel filter though I doubt it's any of that.

For those who don't know what happened, the boat was underway say at 40km/h @ 5k rpm when it suddenly dropped to 20kp/h @ 3k rpm. Then on its own it went back up to speed.

It happened twice and at first I thought maybe I hit the throttle by accident, but I didn't. Then I thought I was running out of fuel, but there was plenty in the tank. Could be a bad batch of fuel maybe?

Today the motor was running great, might just have to try it out again!

Any other ideas?

[johnno]

Have you changed your in line filter ?

Have you changed Fuel filter?

[BWV]

I would be checking the leads and the coil packs, they can give you problems if the have moisture in them or if the leads are slighty damaged. You can can the lead by having a look at the condition of them and feel them for damage of check them for resistance with a multimeter.

May have had some water in the fuel, when you pulled the carbies apart did you catch the fuel that was still in the carbie and check to see if that was water in the bowls?

[oz_brett]

Do you have a water seperator / fuel filter?

it could be water getting in to your fuel system.

DO NOT run ethanol fuels in your boat, ethenol is BAD

[bisso]

Dont know what type of motor you have but i thought it could be an overheat situation.. for example, my motor will drop to 3500rpm when the engine gets to an overheat situation. it is supposedly to reduce the risk of the engine cooking due to the heat soak sustained at high RPM to stop the motor cooking and ultimately seizing. This might not apply in your case but it seems strangley like that is the case. i.e motor now runs fine after that occurred. check your owners manual to see if your motor has a overheat safety situation.

Might save you lots of time and expense changing items that werent required.

Regards

[locodave]

What is an inline filter?

I am going to purchase a fuel filter today and replace it.

With the coils and ignition leads, we visually inspected them yesterday, they all loog good. If there was a problem with them though, I am sure the spark plugs wouldn't be working?

I didn't catch the fuel in the carby bowls.

Now I do remember just before I went on this trip I actually washed out the fuel tank with water. But I also left it out for days to dry. I'm sure there would of been maybe a few drops of water left inside, but I doubt that will be the problem. I am not running a water seperator. It's a 2 stroke 40hp Mariner oil injected. I was told I don't need one for this motor.

I also do remember putting in a tank of ethanol two previous trips ago. I didn't realise I was putting Ethanol in. What are the concerns of running ethanol in the motor? Is it just the seals that wear out easier?

THanks for everyones replies

[tuffy]

What is an inline filter?

I am going to purchase a fuel filter today and replace it.

With the coils and ignition leads, we visually inspected them yesterday, they all loog good. If there was a problem with them though, I am sure the spark plugs wouldn't be working?

I didn't catch the fuel in the carby bowls.

Now I do remember just before I went on this trip I actually washed out the fuel tank with water. But I also left it out for days to dry. I'm sure there would of been maybe a few drops of water left inside, but I doubt that will be the problem. I am not running a water seperator. It's a 2 stroke 40hp Mariner oil injected. I was told I don't need one for this motor.

I also do remember putting in a tank of ethanol two previous trips ago. I didn't realise I was putting Ethanol in. What are the concerns of running ethanol in the motor? Is it just the seals that wear out easier?

THanks for everyones replies

Uh-oh, ethanol - slow death for outboard motors. Also, check your breather on the fuel tank.If it's a portable tank the breather screw on the cap sometimes has a habit of vibrating closed which will cause intermittent fuel starvation - revs will drop until the pressure is reduced and then it will fire up again. Alternatively, if your tank is an underfloor unit also check your breather hoses for any blockages.

Cheers, Tuffy

[bluebottle18]

In regards to fuel I suggest you avoid using Optimax as it only lasts six weeks before it begins to deteriate.

Dont let it sit idle in tank for more than 4 weeks.

Nothing wrong with fuel if you reguarly use it. It just doe`s not like sitting around in your tank for too long.

[rickb]

I have 3 40ltr tanks,a couple of times I have forgot to change

around tanks,one time my end tank sat for 4mths,when I hooked it up went like a dream for two trips.

If you used Ethanol your lucky your motor still goes.

That is a big NO NO.

Its not like the old days when oil was mixed,if you did not use it for a month

It would look like a sheila's hair net.

Cheers Rick.

Edited August 22, 2010 by rickb

[Jewdreamer]

One other thing you could check is the fuel connector to the motor.

If the thing is not on tight and/or the seals are crook your motor can suck air.. looks a bit like fuel starvation.

Happened to us once..

Worth a look!

Cheers

Chris

Thought I'd stick up a post or two since I cant go fishing!!!!!

[Day's Fishin]

My 2cent's worth would be fuel starvation. Filter partially blocked either in line or main. Sucking air somewhere. Ethanol is a death toll for outboards. If you have to clean out the fuel tank then make sure you put some metho in the tank when you fill it up, the metho helps to evaporate any moisture left and a small amount of metho will not hinder the motor.

Regards Jeff

[spaners]

When it plays up does it run rough or just lose power?

If it runs rough its droped the spark in one or more cylinders ie plugs,leads,coil pack etc.

If it is not running rough,but has no power I would look at fuel supply.

Or option 3 you might of broken the sheer pin on the prop...I got caught once with that,went fine till it was under load then started to slip.

Just my thoughts,good luck.

[locodave]

Hey guys,

Thanks for all your replies. I went up to buy a fuel filter the other day and ran into a marine mechanic, so these are the options.

Next time it happens, take off the cowling and pull the plugs, see which spark plugs are hot and which ones are cold. That will indicate which ones are firing or not.

From there we can see if it's just one, can be the coil. So grab that coil and put it on another cyclinder, see if it happens again. If it happens just to that cyclinder then it's the coil. If it happens to the other cyclinder and doesn't look coil related, it can be the stator.

When the engine dropped revs, it was running rough. By the time it happened again I couldn't tell though.

[spaners]

Hey guys,

Thanks for all your replies. I went up to buy a fuel filter the other day and ran into a marine mechanic, so these are the options.

Next time it happens, take off the cowling and pull the plugs, see which spark plugs are hot and which ones are cold. That will indicate which ones are firing or not.

From there we can see if it's just one, can be the coil. So grab that coil and put it on another cyclinder, see if it happens again. If it happens just to that cyclinder then it's the coil. If it happens to the other cyclinder and doesn't look coil related, it can be the stator.

When the engine dropped revs, it was running rough. By the time it happened again I couldn't tell though.

When its running rough,grab a pair of insulated pliers and pull a plug lead off,If the engine runs worse or stalls you know that cylinder is good,now if there is no change that is the faulty cylinder.Then do the same test all cylinders.Once the faulty cylinder is found then you start to swap swap plugs,leads,coils in that order.

Regards Stu.