Optimax 225 running very rough

[Martin_80]

Hello,

I'm running out of ideas here. The problem changes, sometimes it's idling fine but in gear starts to struggle, mostly and right now it idles very rough and stalls. AND sometimes, 3 times now it all goes away and it runs just fine, but that change when leaving the boat over night.

I've checked fuel and air pressures and they are fine.
No gas in the air schrader valve.
Checked all coils, temp. sensors and all injectors except nr6 direct injector (lower cowling is in the way) and all ohm-values checks out.
I've tried a used crank position sensor but that didn't change anything. Checked the wires going to the ECM, connection seems fine and also no connection with ground.
I've put in a new low pressure pump, no change.
Both TPS have about 50hrs on them.
I took the vapor apart for a quick look and the needle valve was at least not stuck and the filter on the high pressure pump was clean.
Primer bulb stays hard.

It's from 1999 and has the simpler warning light and the check engine light comes on, pointing towards a sensor or injector. A DDT scan "Running test" showed problems with the original trigger (crank position sensor) but I think it unlikely that two sensors fails in the same way, but I don't now the status of the used one I tried, I didn't run the DDT with this sensor. My guess is since the engine rushes or jumps up and down in rpm at idle and the ECM hasn't ordered an rpm increase it believes that the CPS is returning a bad value. Also the check engine light mostly come on when giving it some throttle, but it runs like crap idling but doesn't always light up the check engine light.

Turn the volume up!



I've done one test run. At the end it completely died on me, it was hard to start again and it would only run for a couple of seconds. I let it sit for 5-10min and now it ran a little longer and I noticed that if I pumped the throttle it would stay running.



I got back to the harbor and when I was close to my dock I realized that it was running better, I tried to provoke a stall but failed. I then thought I give it another go!


It ran fine!



I returned the day after and it behaved again like in the first clip.


I'm thinking that bad coils or injectors would not cause all this roughness it should be something bigger, ignition timing or fuel supply. Since it doesn't sneeze or popp that would point to something else like fuel or air supply but pressures checks out.

Any thoughts?

[XstreamVking]

I would throw a set of plugs in it....Look closely at the old ones coming out too....If you haven't...

[Martin_80]

Friday evening. Motor ran like ****. I checked each coil with a timing light and they all fired. Dead end. Went home.
Saturday evening. First crank and it ran fine, but did stall a few times. This isn't the first...it can change like this from day to day... I put in new plugs anyway and it ran fine after. To windy today to go out and it usually runs fine when it has a good day.

I will see again tomorrow if there is any change.

[2jz]

Exhaust back pressure might be causing rough idle and stalling. In first video with motor idling the bobbling in water is exhaust gas coming through lower unit because exhaust relief is clogged. Check exhaust tube in cowling if clogged,pull lower unit off and with flash light look up through exhaust port opening you should see relief holes. My optimax had relief holes clogged and with brake cleaner,engine degreaser,long metal rod to help breakup carbon build up.

[vnemous]

what condition your battery in?

[Martin_80]

Yes back pressure can be tricky. When I had a broken reed (Boysen carbon thankfully) it would idle fine on the hose but when in water it would go up and down slowly from say 450-700rpm. It also lost some power but ran fine otherwise. A friend has also commented that my motor makes lots of bubbles, he has a 200hp... My tech looked and said it was fine. Now when you mentioned it and I have not thought of it until now, I don't think any exhaust comes out of that hose. I will take a closer look, I don't think that it will cure my current issue but it should work as intended... Thanks for pointing me to this issue!


I have a optima blue top battery that meet and exceeds the requirements from Mercury, BUT it's not new of course. I've thought about it that maybe something tricky is going on with my battery, but since they are really expensive I'm not eager to buy I new one... I've measured the battery while cranking and it appears fine.

[Martin_80]

Like most days, today was a different day It started right up and ran fine for about 10s, then you could hear that something changes, the idle goes up just a little, it starts to shake and runs rough. After a while it settled down again and idled just fine. I then gave it some throttle (foot) and it had a miss coming up to 2000rpm it suddenly drops down to about 1600-1700rpm for a split second and then back up again. I thought it was a good time to get my timing light, I shut it off and went to the car to get it... Put the light on #1 but now the sudden drop at 2000rpm was gone. I tried to provoke with the throttle but nothing. I checked all six and from what I could see there was no issues. There are no timing markings on an optimax, all I can do is have the light facing towards me and see that the timing has no dead spots, probably pretty hard to see...


How does an older V6 behave when the timing is off? Shouldn't there be some pop or other noise?

[vnemous]

Just a for instance...............today my 300x ran fine last time it was in the water. Today at the ramp it started fine but sneezed a little and the idle was lumpy, lumpier for an X. Ran down the river tach was all over the place and my water temp analog gauge stopped working. Than motor started stalling like the key was turned off. Would start right back up. Would idle and die, start right back up. Idle, get on plane than die. Start right back up. Got to some shallow water and pulled the cowl, everything ok. Disconnected the analog water temp gauge, brown wire in harness and shorted it out and the gauge didnt move so gauge is shot or main harness has a problem. So I disconnect the wire from the back of the gauge and guess what??????? Everything is fine now like a new motor. These things are so finicky to the electric current it is getting..FYI JMO for what it worth

[Martin_80]

I have a friend that used to work as a merc mechanic. He told me on one occasion he had an older merc acting strange and when he disconnected the tach the problem went away. I've tried that but next time after reading your experience I will disconnect everything!

[vnemous]

check all your engine grounds

[Martin_80]

Ground are checked! No difference! To night I disconnected temp and tach gauge but no, still the same.


This is my latest experiment



Luckily the motor had the perfect bad day, first cranks it would start and stall not immediately it wants you to take one or two steps towards the engine and the timing light, then it will die! After some tries it decided to stay running with a casual miss, PERFECT! It looks like when the roughness comes on the ignition point changes about 1-2cm and when it just is about to stall I think it's more like 2-3 (did get that on film). In my mind that does not seem right but I don't know what the ECM is doing... However on one time I could observe a gap (no light). The motor ran fine after this clip so I went home.

Should the timing be fixed at idle?

At 10s you can hear a miss and see on the tape that the timing changed. Run 1080p!

[150aintenuff]

OPTIMAX will not advance RPM unless CPS OR TPS tells it to... the throttle blade DOES NOTHING if the system DOES NOT see triggering from those 2 sensors it should not vary rpm IF IT DOES then look to reeds or other mechanical issues.

quick question.... have you changed the compressor filter lately.... they are known for causing mystery issues when plugged and NOBODY around here ever services them properly... i pulled a 1500 HR 1998 down the other day with the original air compressor (shot) and original FILTER completely clogged

[Martin_80]

I've ordered a new CPS.

Yes the filter has been changed maybe 150h ago, but I looked at it this spring and it was clean.

[W2F a V-King]

I've ordered a new CPS.

imo...not fuel, but electrical the way that tach jumps around. Almost like your switching the key on and off super fast.
And you did have codes for the crank sensor...

So it's got to be one of three things, or a combination of any of these...CPS, Wiring from CPS to Computer, or the Computer.

And yes, do verify all your power and ground circuits.

I use a home made test light with a fog lamp in it to pull several amps through what ever circuit I am testing. You do have to be careful with it though, you can poke the wrong wire and smoke the circuit or fuse.
A volt meter can read 12 volts on any given circuit, even with a loose corroded connection, but give no indication if that circuit can carry any current.

If you know how to do a voltage drop test on your power and ground circuits, this will do as well. Power and ground circuits run through the ignition key too. I had to paddle out of the 1000 islands of Flamingo Fl. One night with a friend over a dead ignition switch...didn't know it at the time though or I'd of bypassed (unplugged) the main harness and jumped the starter solenoid....

HTH

James

[Martin_80]

I hear you James! Resistance measuring does not tell you if as you say the circuit can carry any current. I understand the principle but this is not something I've done, ever...


I got my new CPS today, sadly the problem is still there. Next I will try and borrow an ECM.