North Australian FISH FINDER TM forums

Hi all,

After investing quite some money in rebuilding my engines swivel bracket and steering arm with all available bushes .... the engine is having some other issues.

It has happened twice now that I can launch the boat, start the engine and get out and about in the harbour without issues.
The engine operates without issues at all rpm's.

One time I drove to Bottlewasher and noticed on the way there, that the revs would go up and down slightly. On the way back it got that bad that I was hardly able to get along.
The last few km through the harbour was Throttle full open and maybe 2000 rpm .... or throttle half open and 2000 rpm and suddenly the engine would rev right up nearly chucking me out the boat.
To me it felt like it was starving for fuel.
I still had a new fuel pump diaphagm kit at home which I held as a spare. As it felt like the the engine wasn't getting enough fuel, I put the new kit in.

Hoping that it was all good now, I launched the boat again yesterday. Driving around in the harbour again was fine. Trolling up to six mile was good too, but as I accelerated to get over to Lee Point, the same thing started again.

I have a 1994 - 96; 115 HP; 2 stroke Mercury.

Has anyone got an idea what this could be, or know a mechanic who doesn't charge an arm and leg for having a look and assessing ?
Keeping in mind that the issue doesn't occur within a few minutes of driving around with the boat.

Funny is that it works fine for quite a while until it suddenly has these issues.

No, I haven't replaced the fuel filters yet. I have one big one above the tank and the in line one in the fuel lines.

Cheers

Tim

Could be starving of fuel, does it seem to run badly and miss when your at full throttle.and only doing 2000rpm? If so lean towards ignition, might be breaking down under load or when a certain component heats up and expands after running for a while. Hard to find intermittant faults at times just start with the basics.
They should also run some form of mechanical advance for timing, so id be checking that too.
Give me a call.if you get stuck

It actually runs fine without missing a beat over the whole range of rpm .... until suddenly it has enough and can't accelerate .... can't go over 2000 - 3000 rpm with sudden bursts of power nearly flicking me off the boat.

Have you tried changing the spark plugs, hot spark plugs can cause changes in rpm.

Spark plugs are new .... maybe 10 to 20 hours old.

Try the ignition coils, had something similar happen to my merc. I have a 150 opti which had 6 coils on it and apparently when one goes you lose a bit of speed at the top end

Try the ignition coils, had something similar happen to my merc. I have a 150 opti which had 6 coils on it and apparently when one goes you lose a bit of speed at the top end. I think the ignition coils connect to the spark plugs.

Try taking the fuel tank out and cleaning it. There could be some cr.p floating around in it that partly blocks off the outlet now and again. I have a similar problem with one of my under floor tanks that I need to attend to next time I have the floor up.

I have a couple of extra primer bulbs in my lines before the filters so I just pump one of them and it clears it until the next time it blocks up.

mike davis wrote:Try the ignition coils, had something similar happen to my merc. I have a 150 opti which had 6 coils on it and apparently when one goes you lose a bit of speed at the top end. I think the ignition coils connect to the spark plugs.

My bro in law had a similar problem. his brand new merc failed 3 times at sea. every time it was a failed coil.
Brand new and he is too scared to use it anymore.

they dont call em black anchors for nothing.

Grumpy ..... Fuel tank is clean. has just been repaired and cleaned out. The issue occurred before the tank repair and after.

Ignition coils sounds like an idea but still need to figure out how to test them.

One thing these engines are supposed to do, is run on two carburetors when under 2000 rpm and then have the other two kick in at a later stage.
That's what a Mercury dealer told me before and I think I've read it too.

The funny thing is that when the controls are at WOT and it just about reaches 2000 or slightly more revs, ..... it suddenly revs up from nothing like suddenly getting enough fuel and thenfailing again.

Might be an idea to have a look at the carburetors too and overhaul them ....

nomad wrote:they dont call em black anchors for nothing.

Nomad, I know where you are coming from, but this engine has hummed away without issues for 5 years that I have owned it and is from 1996 or so.
So far it was far more productive than an anchor .....

Ive heard of more people having dramas with their new poozukis than i have with either of the mercs ive had.

They love 'em down South. Just a Territory beat up that's been around for years.

Like ETECs scottmac. they don't have too many dramas down south in cool water but struggle up here.

I was only taking the p155

Look at the race engines, lots of mercs there.
That might very well be the answer cuddles ! only use them during the dry