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  1. Banned
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    #21
    OOOHHHHH THE GREMLINS of an 11 year old boat!! Good news, it jumped up on plane every time this outing. Bad news, 4900 RPM was all I got and 43 mph. So, what I noticed is that at idle it was rough, wanting to die and had to keep a little pressure on the hot foot and maintain 800-1000 RPM in order for it to not idle roughly. I checked the throttle cable before I went out this time and made sure idle screw was touch and WOT screw was touching. Also the seals on the screws are still intact and look like they are still set to factory. Did some browsing around on here and found that mercury optimax in this generation had some bad coils. Pretty sure someone else mentioned this earlier on in this thread as well. Since this boat is new to me, it felt better than last time but I know a 100 rpm increase with 4 pitch sizes smaller is not right. Well the symptoms I read about in the earlier thread was 10 mph loss at WOT (I wouldn't know since this boat is brand new to me), only being able to max out at 4900-5000 RPM, slower holeshot (again wouldn't know because the holeshot this time was a helluva lot better than last time), and rough idle. SO I am definitely experiencing 2/4 and thinking now that I need to check coils and plugs asap. I did read about a service bulletin 2009-026, which is I'm guessing something like a recall? Anyone have any information on this? If not, I will buy the new coils and new plugs and replace and hope that helps. I read that it is impossible to detect on the ECU a misfire on 2 strokes so here we are. I will also be starting a thread on the Mercury outboard forum, probably more appropriate.

    Also, I noticed absolutely no rooster tail today despite trimming all the way up. I do realize I am still too low and will be putting a JP on soon. But that didn't help the RPM situation at all either.

  2. Member
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    #22
    I think its time to get that motor checked out for sure. On the coil thing your symptoms sound right at least how i have experienced them when its happened to me. I have also noticed if i run the boat on muffs that the motor sounds really flat at idle, normally the exhaust has some pop to it. If i remember correctly that service bulletin is about how to troubleshoot the issue, not really a recall.

    You are correct in saying the ECU wont detect it. When i had one fail under warranty the mechanic at the dealer claimed that there was nothing wrong with my motor and that i was over-propped despite the prop being the one that was delivered on the boat from Nitro( modified but the same prop). After a little back and forth with him and the service manager they went beyond just plugging in the ECU and they found the bad coil. I took the mechanic back to the lake down the street for a water test after the fixed it and im pretty sure he crapped his pants when i took him for a wide open 70mph ride. He had never been in a bass boat before prior to this...

    As far as your boat i would not just buy 6 coils and parts swap it, that will get real expensive especially if it does not fix it. The current OE merc part is like 140 bucks each. I think finding the problem is important and you should be able to find the offending coil pretty easy. Run it on muffs in the yard and listen to it, if it sounds flat like i mentioned before you probably have a bad coil. You can find it by pulling the plugs post run. If you find one that is wet you have found the bad coil. The other way is with a timing light, use an old school timing light on each coil and the offender will be easy to find, the light wont pulse. I would just replace the bad one and be done. On my boat i have had one fail 3 times in the first two years i owned the boat, every time it has been the bottom one on the starbord side. I have kept a spare coil in the boat for 10 years now and while i have never needed it i like having one since i can easily troubleshoot and change it on the water.
    Last edited by jb882; 09-14-2020 at 09:31 AM.

  3. Banned
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    #23
    Jb, I have seen videos of a timing light being used. My only issue with this is again I am not sure what I'd be looking at. I would assume that the light would flicker constantly and in a normal pattern. If the pattern was messed up, then it obviously isn't sparking correctly. I get the concept of these but I have never used one. Now, this could be plug related or coil related so I would move the coil to a new cylinder and see if the problem follows the move of the coil. I plan on doing all of the plugs anyways. With all used motors that I acquire, I usually do full maintenance on them. Unfortunately, with this motor, I trusted the 9 page report from the computer that said "no faults" and since this optimax is completely new to me, I didn't realize some problems could arise without detection. So here I am but from the multiple threads and forums I read, it sounds like a spark or misfire issue somewhere in the motor. My girlfriend works at a Mercury dealer just up the street. I will probably have their guys go through the motor top to bottom as well, I just hate having to take it to people for simple jobs that take a little time. I have always done my own maintenance stuff on motors, from cars to lawnmowers, etc. So, in some ways I don't want to and want to be able to diagnose and correct issues on my own but I think this wouldn't be a bad idea to do at this point since the motor is 12 years old, wasn't ran very much in its life, and who knows how long it had been sitting before I purchased. Guys, thank you for everything so far. An absolute wealth of knowledge here.

  4. Banned
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    #24
    Old post but finally changed all 6 plugs. Going to order a few more to have on hand and wasn't thrilled that one of the new ones I pulled out of the box was gapped at 0.42 so I bent it back down to 0.32-.033 as recommended, but not a good feeling to have to bend back a plug to specs and hope it keeps working. All others ordered were gapped correctly out of the box. JB, when I put it on the muffs, it sounded mean as hell, growled and sounded much more different like you had stated. Completely new animal compared to what I had heard the first two times out on the lake. Granted it was out of water but I think I understand what you were talking about in regards to sounding flat because when I picked up the boat, I turned the key and made sure it would run before running to the lake and let it run for 3-4 seconds and it sounded flat then. The plugs I pulled were fouled and looked to be very old. 3/6 had gaps of 0.38-0.4 and the other 3 were within normal range, but again black and fouled. New plugs and new fuel filter done and gas inspection in filter looked really good still so not too concerned with visual of fuel, going to change the livewell pump to a 1000 Gph pump since it died last time out as well. Don't look forward to pulling batteries and oil resevoir to get to it but it needs to be done.

  5. Moderator Fishysam's Avatar
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    #25
    Quote Originally Posted by flashman252 View Post
    Old post but finally changed all 6 plugs. Going to order a few more to have on hand and wasn't thrilled that one of the new ones I pulled out of the box was gapped at 0.42 so I bent it back down to 0.32-.033 as recommended, but not a good feeling to have to bend back a plug to specs and hope it keeps working. All others ordered were gapped correctly out of the box. JB, when I put it on the muffs, it sounded mean as hell, growled and sounded much more different like you had stated. Completely new animal compared to what I had heard the first two times out on the lake. Granted it was out of water but I think I understand what you were talking about in regards to sounding flat because when I picked up the boat, I turned the key and made sure it would run before running to the lake and let it run for 3-4 seconds and it sounded flat then. The plugs I pulled were fouled and looked to be very old. 3/6 had gaps of 0.38-0.4 and the other 3 were within normal range, but again black and fouled. New plugs and new fuel filter done and gas inspection in filter looked really good still so not too concerned with visual of fuel, going to change the livewell pump to a 1000 Gph pump since it died last time out as well. Don't look forward to pulling batteries and oil resevoir to get to it but it needs to be done.
    So my plugs are supposed to be 042, yours being the closer o32? Is probably set up for a multi spark firing where as my 2015 is a single. Just one of them neat things I have learned from this site
    Mercury 250 proxs 2B115089

  6. Banned
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    #26
    fishy, all I know is when searching the 2.5L mercury FAQ area, my serial number calls for a certain set of NGK and the gap is listed at 0.32-0.33. Interesting that half of my plugs were at the 0.32-0.33 and some were around the 0.4-0.45 range. All were the correct plug part number that I pulled out. Again, they looked real old, and I bought the boat from an old timer that never touched a thing on it. For the 10-11 years he owned it, the motor only had 105 hours on it. I expected some small gremlins when purchasing it and just working through them slowly. In regards to you talking about mulit-firing and single firing, that is way above my level of knowledge. I read ingredients for these motors and follow them to a T and hope the motor does it's job when I put in the correct recommendations.

  7. Banned
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    #27
    Jb882, able to get spark plugs done, fuel filter changed, and took out strainer to ensure it was clogged up. Put it on new muffs and got it to start pissing really good at 20 seconds of being fired up. I know you mentioned a flat sound. So I took video of the motor and maybe you can take a listen and see if it sounds about right or if it has that same flat sound you mentioned when your coils went out. I think it sounds better and I plan on taking it to the lake Saturday and making one more test run before I put it away for the winter. I appreciate you (and anyone else who chimes in) taking the time to listen, just a 30
    sec video.


  8. Member
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    #28
    It sounds a little flat to me, the exhaust should have more growl to it when its out of the water. How did the old plugs look when you took them out? If you have one that shows signs of not firing it would be a telltale sign that something is wrong.

  9. Banned
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    #29
    They were all junk jb. Replaced all 6, 3 of them were gapped 0.40-0.45. All were terribly fouled. Not sure they had ever been replaced. Ran it this morning, 5400 rpm at wot, idled great, ran like a champ and was on plane in 2-3 seconds. So I think it’s doing better. It’s at least running. I’m still going to maybe pull coils and test them to see if they are all still good.

  10. Member
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    #30
    Quote Originally Posted by jb882 View Post
    It sounds a little flat to me, the exhaust should have more growl to it when its out of the water. How did the old plugs look when you took them out? If you have one that shows signs of not firing it would be a telltale sign that something is wrong.
    I would just pull plugs. Would be obvious if one is wet compared to the other new ones you’d have a bad coil. If they are all the same you should be good to go, sounds like it’s running fine now.
    2020 Nitro Z20 Pro Package

  11. Banned
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    #31
    Mcjenson, I will definitely do this next spring next time I run it at the lake. Boat is getting winterized this weekend and then I will come back to it next year. I definitely need to do a water impellar, only seeing 10 PSI at 5400 rpm (and im sure that has never been serviced if the plugs were any indication) but I was seeing 2-3 PSI at idle (which is normal). Plan on adding a JP because my Prop to pad is 3.5" and it appears that 2-2.5" is the sweet spot on these z7's. I want to start plugging PVS plug holes because the hole shot is quick quick now but only saw 47-48 with me and one other person in the boat and half full livewells and half full fuel tank. It has more there and I can afford to give up a little hole shot now and gain a little top end. Hoping lifting the motor with the JP will get me closer to that 5700 RPM that is WOT on my motor. Guys thank you for the recommendations and all the help thus far.

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