Mercury Optimax 115 - vibration

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    Posted: 07 Feb 2021 at 10:41pm
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Bad day today......2 kms from the ramp, slowed to checkout a workup and noticed outboard vibrating. Stopped and turned motor off to do a visual check.......nothing obvious, so attempted to restart to return to ramp. Motor started but cut out if I dropped revs to idle to engage forward gear. Managed to get it to run in gear and gently cruised home at 5 knots but definite gentle surging noticed and no response if I opened the throttle (thinking dirty fuel at this point!!). At ramp, checked everything incl. filters ( all clear) and started motor. Ran perfectly in neutral, nice and smooth at higher revs (water tell-tale fine at every point). 

BUT.....put in forward gear at idle.......vibration (couldn't tell from where). So I'm presuming a gearbox issue?? Will drop oil out tomorrow then remove leg .........but am I on the right track? 

Thoughts please ladies and gents. Any assistance greatly appreciated!!

Murphy's law.......we are heading north for our 10 day summer break at Whangarei Heads next weekend so really need this to be solved this week Unhappy
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Post Options Post Options   Likes (0) Likes(0)   Quote bigred1 Quote  Post ReplyReply Direct Link To This Post Posted: 07 Feb 2021 at 10:52pm
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Does it still happen if the prop is removed? (Just thinking of easiest things first).
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Post Options Post Options   Likes (0) Likes(0)   Quote bricker Quote  Post ReplyReply Direct Link To This Post Posted: 07 Feb 2021 at 10:58pm
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That will be first on the list tomorrow.....then process of elimination from there. At least I can replace the waterpump impellor whilst I have the gearcase off!!!!
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Post Options Post Options   Likes (0) Likes(0)   Quote bricker Quote  Post ReplyReply Direct Link To This Post Posted: 08 Feb 2021 at 8:49am
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So....update....pulled out spark plugs - 2 blackened but with white tip & 1 blackened with no white tip, just coked up. Put plugs back in, turned key, motor tries to start ....pops and almost fires when rev lever moved but doesn't really want to pay ball. Last time out we went to see Prada Cup......lots of traipsing about at 5 knots as launched from Bayswater and whole of inner harbour was a 5 knot zone!!!

So maybe only firing on 2 cylinders therefore vibration, reduced revs/power??? New plugs then we will see if situation alters??

Flying blind here, so any insight welcome.
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Post Options Post Options   Likes (0) Likes(0)   Quote bricker Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb 2021 at 9:59am
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Concluding update........it transpires faulty oil reservoir float sensor intermittently sending random messages to engine management system!!! Hence this triggered engine to shut down into "limp home' mode.

Good to see this type of technology working as it should.....in spite of the cause being a faulty sensor!!!
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Post Options Post Options   Likes (0) Likes(0)   Quote smudge Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb 2021 at 2:06pm
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Wow, last thing I would have thought. My guess was a fouled plug Big smile. Did you get away for your holiday?
Best gurnard fisherman in my street
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 01 Mar 2021 at 9:45am
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it transpires faulty oil reservoir float sensor intermittently sending random messages to engine management

 Not uncommon, usually if there is a little water in the tank... rather than faulty sensor.. chances are all that was needed is the tank cleaned out.. there is not much that can go wrong with the sensors

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