'93 25hp 2 stroke Spark Plug Issue??

[TownsendsFJR1300]

Congrates!!

Wish all the fixes were that easy!!

[Jason2tpa]

I agree...tho for the stress is the same big fix easy fix= No boat time!

Congrates!!

Wish all the fixes were that easy!!

[rodbolt17]

there is a reason that NO standards are listed.

how many met/cal compression testers have you seen?

how many come with certification tags and a recert date ?

therefore the standard is 10 PSI highest to lowest with the same tester on the same day.

torque and 3/4-1 turn past finger tight are WAY WAY different things.

it will torque all day long.
the 3/4-1 turn past finger tight ONLY works with new plugs on the FIRST install. try the turn method twice and you get to post about thread repair on the holes.

[Jason2tpa]

Wish i knew that lil pearl about first time plug threading!! Luckily im smart enough to have known not to overtighten. As far as your question about compression my answer is i dont know the first thing about the intricacies of compression testing. Other than its used to assess the performance of the cylinder. But help me out please. I asked what the standard or manufacture recommended compression is for my engine. Your saying this standard, or lack thereof, varies with tester?

there is a reason that NO standards are listed.

how many met/cal compression testers have you seen?

how many come with certification tags and a recert date ?

therefore the standard is 10 PSI highest to lowest with the same tester on the same day.

torque and 3/4-1 turn past finger tight are WAY WAY different things.

it will torque all day long.
the 3/4-1 turn past finger tight ONLY works with new plugs on the FIRST install. try the turn method twice and you get to post about thread repair on the holes.

[99yam40]

What he is saying is that what you use is not necessarily calibrated to anything or retested on a regular basses.
So Yamaha does not list a spec for it.
Now if there was a very expensive gauge that everyone had to use then maybe there would be one, but then there could be other variables that would come into play

[TownsendsFJR1300]

Both cylinders should be within 10% of each other in any event. If one is MUCH lower than the other, you have an issue. If the engine runs good, full power and your within 10% you should be fine. ( I wouldn't go looking for a problem that apparently isn't there)..

Best checked when warm, engine cranked over several times with the throttle held WIDE OPEN. Engine compression ratio's will make a difference as well..

IDK the ballpark # your engine should be. I have 4 stroke weed-eater that calls for 90-125 PSI(it has 115). I have a two stroke weed-eater that has 195 PSI.

*An internet search for your engine should get you a ball park #. Of course you'll get weird answers but research enough, you'll get a general idea...

[rodbolt17]

and if you test a late 80's 225 jonnyrude you will find about 80 PSI across the board.

[Jason2tpa]

Ok got it. Thanks everyone for the help. I love this forum.

[Dashunde]

You mentioned running it 100:1 and whether or not 50:1 would be better...
I dont think I'd double the oil, but I'd probably richen it up to ~70:1, especially If you spend most of your time cruising at 75% throttle or more.
It's an older engine showing around 90psi, which is ok, but a bit more oil migh seal it up tighter and slow the wear as time goes on.
Check the plugs occasionally for excess carbon.
And ignore all of that if you ***** often.

[Jason2tpa]

My friends yamaha mechanic also suggested 50:1, though he said use synthetic. Your thoughts on synthetic? I'll burn the remaining fuel in my tank and switch.

I dropped the boat in yesterday and she didn't start!!...well the first pull it started bogged down and cut off. this after it working great Saturday. So I trailered back to my storage facility. Pulled the plugs. Gap looked good (new plugs so they should). I tried to start with leaving plug #1 out and #2 in. And vice verse. Eventually it started and remained running on flush. I launched boat and it ran great. Head scratcher. Could it be the carb mix be too rich, covering plug gap with unburned oil? Then it sits a day or two. I take it out and wont fire? The the amount of time i take it out weekly it shud start with one or two pulls each time.

You mentioned running it 100:1 and whether or not 50:1 would be better...
I dont think I'd double the oil, but I'd probably richen it up to ~70:1, especially If you spend most of your time cruising at 75% throttle or more.
It's an older engine showing around 90psi, which is ok, but a bit more oil migh seal it up tighter and slow the wear as time goes on.
Check the plugs occasionally for excess carbon.
And ignore all of that if you ***** often.

[Dashunde]

I've never really used synthetic.. probably a question for the guys who have worked on these things for a number of years.
Unless a motor spends most of its life idling around I'd be hard pressed to stick to that 100:1

You mentioned pulling the plugs, pulling the cord with one in & one out, etc.
You may have simply cleared out a flooded condition?

Do not trust that your new plugs are properly gapped right out of the box.. they usually are not and you need to do that yourself.
This is not outboard specific, it applies to every single gas engine out there.


A couple of thoughts about storage and starting in general...

Disconnect your fuel tank from the motor before storing to prevent fuel being forced into the motor due to ambient temp changes.
(Tank sits in sun, gets hot, builds pressure that forces fuel into the carb and maybe past the floats needle.)
Open the tanks vent before re-connecting to the motor.

Develop a consistent storage, starting and choke procedure.
Its usually: Open vent, connect hose, pump bulb till just firm and no more close choke, open throttle and pull till it fires, then fiddle with the choke a bit too keep it running...
All motors are a little different in what they need after they fire off. Some you close the choke right away, some go half closed, others need in/out a few times.
And each will vary depending on how hot/cold it is outside.

If it doesn't fire off after just a few pulls, remove a plug and see if its wet... this will tell you something about future starts and how effective your choke is at drawing fuel in.

If its soaking wet... now, this is what I do, and it always works, but some may cry unsafe foul, so be it...
I put a match in a pair of needle nose pliers, light it then stick it into the spark plug hole, if its very flooded I'm instantly greeted by a "Woot", lightly flooded will just blow out the match.
At that point the cylinder should be fairly un-flooded and ready for another try.

If the plug is dry... put the plug back in, close the choke, pull a few more times and check the plugs again if it doesn't fire off.
If the plug is still dry check that choke does, in fact, actually close and if it does then you've got a carb problem - float stuck closed, clogged needle/port, etc..

[Jason2tpa]

This is all really good advice buddy thanks. If the plugs are indeed fowling because of the flooding, is it because the mix is too rich? I regularly flush at idle after running boat. So i cant see how this would flood. Why would there be gas leftover in the cylinder? But I have been completely closing choke valves when starting, then opening to half then full open. Perhaps i should reverse these steps, especially since the engine rarely sits more than a few days? It might not need to be choked. Btw, i also posted a new thread about the tell tales of the plug surface. Check it out and let me know what you think.

I've never really used synthetic.. probably a question for the guys who have worked on these things for a number of years.
Unless a motor spends most of its life idling around I'd be hard pressed to stick to that 100:1

You mentioned pulling the plugs, pulling the cord with one in & one out, etc.
You may have simply cleared out a flooded condition?

Do not trust that your new plugs are properly gapped right out of the box.. they usually are not and you need to do that yourself.
This is not outboard specific, it applies to every single gas engine out there.


A couple of thoughts about storage and starting in general...

Disconnect your fuel tank from the motor before storing to prevent fuel being forced into the motor due to ambient temp changes.
(Tank sits in sun, gets hot, builds pressure that forces fuel into the carb and maybe past the floats needle.)
Open the tanks vent before re-connecting to the motor.

Develop a consistent storage, starting and choke procedure.
Its usually: Open vent, connect hose, pump bulb till just firm and no more close choke, open throttle and pull till it fires, then fiddle with the choke a bit too keep it running...
All motors are a little different in what they need after they fire off. Some you close the choke right away, some go half closed, others need in/out a few times.
And each will vary depending on how hot/cold it is outside.

If it doesn't fire off after just a few pulls, remove a plug and see if its wet... this will tell you something about future starts and how effective your choke is at drawing fuel in.

If its soaking wet... now, this is what I do, and it always works, but some may cry unsafe foul, so be it...
I put a match in a pair of needle nose pliers, light it then stick it into the spark plug hole, if its very flooded I'm instantly greeted by a "Woot", lightly flooded will just blow out the match.
At that point the cylinder should be fairly un-flooded and ready for another try.

If the plug is dry... put the plug back in, close the choke, pull a few more times and check the plugs again if it doesn't fire off.
If the plug is still dry check that choke does, in fact, actually close and if it does then you've got a carb problem - float stuck closed, clogged needle/port, etc..

[Jason2tpa]

Fantastic info, thanks!

the issue with the plug threads is simple too.
its called a fire ring crush gasket that technically can only seal correctly once.

once crushed its simply crushed and is now simply a washer.

means there is no 3/4-1 turn past finger tight.

back in the day you could actually buy them at the parts store.
may go back two days.

[TownsendsFJR1300]

How "much choke you need" also depends on the ambient temps...

If its 40F outside, you likely need full choke. If its 85F, you probably might need 1/2-1/4 choke.

As noted above, each engine has its own idiosyncrasy's.

One day, try little to no choke when cold and its warm outside.

If your flooding it a good part of the time, lighten up on the choke, its plain too much fuel..

[Dashunde]

Does it smoke a bunch when it finally starts?
If so, its a sign of flooding.

If your letting it idle for awhile during flushing it could be loading up slowly during that long idle, especially if its a bit rich... even at 100:1?? I dunno...
IF it is loading up, and its not cleared out before its shut off it could make it hard to start next time around.
(We have one particular SeaDoo with twin carbs that'll get very pissy on its next start if its not blown out on the hoist after the long no-wake idle down to our dock. Big blast of blue smoke every time, been that way since new ~2001)

Disconnect your fuel line while flushing/idling... that should empty it out, carb and cylinders both.
When its time to start again, pump your bulb till it firms and hold a wee little bit of pressure on it for a couple of seconds, you may feel it collapse some as the float bowl fills up again, if so squeeze it gently once more to firm back up.

The plugs could be fouling because of flooding combined with a too small gap.

When cold, it should be started with the choke fully closed and as much throttle as it will allow in neutral.
IF it fires, but does not start, THEN open the choke for a few pulls, if it doesn't fire again then close the choke once more to draw in more fuel.
The objective is to get enough fuel in there to start, but not so much it floods. Sometimes, being quick to open or half-position the choke when they sputter to life will save you a few more pulls.

I have never come across a 2-stroke that will cold start without choking, even after sitting for just 10-20 minutes most needed that additional sip to get going again easily.