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115 Optimax misfring - STOMPED !!!

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White Lake Dan

New member
So. My 2007 115 Optimax is misfiring.

It does not stall or shut down. It just misfires erratically at idle (and at speed). Just every 15-30 seconds or so and just for a second or two maybe.

It has been at the shop for 2 months now and still no cure. The serviceman has pretty much changed and checked it all. Mercury, too, is stomped and has little to offer but they are sending in a trial replacement "computer" to see if that works.

One thing for which I have a question for you guys is this:

The injectors should read between 1000 to 2400 ohms to ground as per specs. 2 are fine as one is 1500 and the other around 2000. The other, though, shows 800 ohms. That is 20% under spec. I'd have to shell out over $500 for a new one and that is non refundable and it may fix nothing.

Question: Can that 200 ohms shortfall cause misfiring you figure???

Thanks

Dan at the lake with no boat!
 
You need to do a cylinder drop test to narrow the problem down. Run the engine on the muffs and with the cowling off. With a pair of spark plug puller wires (or any other pair of pliers with good electrical insulation,) pull each plug wire off the spark plug for a few seconds and push it back on, one at a time. If you hear a change when you pull a plug wire off, that's good. That means the cylinder is firing. When you pull the plug wire off and there is no change, then you have found the cylinder that isn't firing or is misfiring. Then, you can focus on that cylinder and go from there. Do a spark & compression check on the misfiring cylinder. If those check out, you can swap fuel/air injectors with those on a good cylinder and see if the problem follows it. If it's still misfiring, you need to check your reed valves. Let us know how the progress goes.
 
LSXG8GT said:
.... Let us know how the progress goes.
Click to expand...

Well, thanks for the great tips, which I passed on to my mechanic, but he had done all these tests (and changed the reed block) but still no-go. He's waiting on a replacement trial computer from Mercury to see what that does. I'll keep you posted on what turns up.
Thanks again.
 
Ask your mechanic if he has disconnected the MAP sensor and run the motor with it disconnected. If it's "not there" the ECM will "pretend" that it's and will read what it would expect to see from it.

Your symptoms do sound similar to other issues I have seen where the MAP was the culprit - and of course it always showed good because it was intermittent enough that it never threw a code....

Something else to check out...
 
Well, everything suggested here has been tried! Still no go! The misfiring, if anything, is now worse. A Mercury Service Advisor was even over at the marina with no positive results. The mechanic is at the end of his rope, Mercury can`t figure it out. it is just weird that such a seemingly simple problem can`t be found. I have asked the Marina owner to contact Mercury to see what the heck to do next. I`ll find out next week. Most frustrating!
 
Send the fuel injectors out for professional cleaning and testing. Buy 1 new CDM and replace 1 at a time to see if it stops the miss. Did the mechanic pull the flywheel and visually inspect the trigger coil?
 
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White Lake Dan said:
Well, everything suggested here has been tried! Still no go! The misfiring, if anything, is now worse. A Mercury Service Advisor was even over at the marina with no positive results. The mechanic is at the end of his rope, Mercury can`t figure it out. it is just weird that such a seemingly simple problem can`t be found. I have asked the Marina owner to contact Mercury to see what the heck to do next. I`ll find out next week. Most frustrating!
Click to expand...

Did they look at the reed valves? Has the misfire been narrowed down to any particular cylinder(s) yet?
 
It's an Optimax - the only thing that goes through the reeds is the air and the oil for the cylinder - the gas is "direct injected"..
 
Indeed, the reed valves were changed and as far as I know the mechanic was not able to narrow the misfiring to any particular cylinder (why, I am not sure).
 
I know the mechanic was not able to narrow the misfiring to any particular cylinder (why, I am not sure).
Click to expand...
A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :) per galamb
 
Well. Mercury's "top tech" is on his way to my boat as the thing is still down and out. I was also presented with a (running) $4,097 bill for the work done so far!!! This ain't over by a long shot and the whole ordeal has been frustrating beyond belief. I'll keep you posted.
 
Try to negotiate the bill since they failed to fix it. Either they are incompetent and just threw parts at it or the problem is unique even to Merc. I would try to get Merc to eat some of the repair cost. They don't want their engine problem to get out to future buyers and the repair shop doesn't want their name on the WWW as an incompetent shop. Speak calmly and use terms as "I would rather see this event as a win win issue and not a you win and I lose event". Good luck.
 
if that repair shop is a member of the BBB then you can arbitrate the bill...they are bound to the arbitration decision..you are not.
 
Well... Problem solved (?)

Just got a call from the Merc Tech who was with the boat this morning. The boat is now "perfectly fine" according to him. The very last thing that he suggested changing was the Poppet Valve. I'll be out later today to test the boat but it sure appears that that might have been the problem all along?

As for the nasty bill, the Marina owner is willing to wave a good bit of it so we'll see !

Does this Poppet Valve explanation make sense to you, the more tech-savvy folks?

Thanks again all for the good tips.
 
Poppet valve allows more cooling water through the block under high pressure...valve pops open under pressure.
 
It will be new to me if the poppet caused a misfire.

A poppet might cause an overheat alarm over 1500rpm due to not opening.
A poppet will cause the motor not to warm up to operating temp due to being stuck open.

Maybe the misfire is due to it stuck open and cold fouling the plugs.

Hopefully your problem will be solved. :)
 
Well, it's like this. The boat is fine now.

The last thing changed was the poppet valve. The Technician says that the motor was still misfiring immediately after doing so. The boat then sat for a few days until the Merc Rep showed up and actually did nothing to the boat but fire it up. Then, mysteriously, the motor works perfectly well for him!

After some 4 months in the shop and (almost) everything changed, the motor is now like new. As for the final bill, the owner slashed it by nearly 60%! I was not expecting that much but it is most welcome. They'll write it off as a good learning/training experience, I guess. I live on the lake, the Marina is on the lake. We're a tight, small community and this showed in the end where reasonable compromise was made. We're both ok with this now.
 
Good to hear the motor is running well.

The marina didnt by chance have your battery on charge for the few days it sat?
Weak batteries cause havic with Optis.
 
Optis need a lot of amps to run correctly. The wrong CCA battery or a slightly run down battery will cause misfire, error codes and other problems. The alternator charges the battery but the battery needs to have full power and be of minimum requirements to fire the coils etc. There is a lot of information regarding tis on the BBCBOARDS http://www.bbcboards.net/motor-forums/
 
magnum19 said:
Optis need a lot of amps to run correctly. The wrong CCA battery or a slightly run down battery will cause misfire, error codes and other problems. The alternator charges the battery but the battery needs to have full power and be of minimum requirements to fire the coils etc. There is a lot of information regarding tis on the BBCBOARDS http://www.bbcboards.net/motor-forums/
Click to expand...
I relocated my battery to the bow and have had misfire issues since. Wonder if adding cable could be the issue? Nothing showing on ECM .no codes or alarms
 
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