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Old 07-26-2009, 10:53 PM   #1
Lt. JG
 
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Default Intermitant Fault with mag 350 MPI

Hi & Help, bought 1st boat couple of months ago, Maxum 2700SCR (2003) only 60 hrs on engine, been fun up to a few weeks ago, now 74 hrs on engine

Problems-
1) Notice leaving marina at idle engine missed a beat every now and again, put on plane @ 3500 revs and seemed fine, out for a hour or so returning on plane felt it miss again, came into marina and ticked over fine
2) Went out from marina and the odd miss again, just onto plane @ 4000 revs when dies, heavy smell of fuel, tried to start would occasionally fire but then splutter to a halt, towed home, back at marina fired up and ran for 15 mins at idle no problem
3) Replaced fuel/water separator filter, on draining fuel from old filter it was very dirty – no water, changed inline fuel filter as well and again really dirty from inlet side, took boat out and tested for an hour ok at all revs, thought problem fixed
3) Went out for weekend, no issues at 1000-2000 revs to destination, stayed the night, next day headed for supplies, all well for 30 mins while waiting to dock spluttered to a halt again, wouldn’t start, 1 hour later got started, running really rough, using high revs to keep running sounded like missing on a few cylinders starting and stopping then all ok, limped back to destination between 700-1000 revs never missed a beat, fired up a couple of time during the night all well, fired up in morning for 30 mins before heading home again all well, loaded up kicked in reverse and spluttered to a halt, tried over an hour to start, would occasionally start but splutter and die, towed home again
4) After being towed back tried to start at marina and wouldn’t so hey hopefully find the problem now, an engineer looked at it and she still would not start, he checked fuel pressure - ok, removed plugs pretty dirty so cleaned and re-gapped - engine now fires up but would shut down after anything from 30 seconds to 2-3 minutes, purring away then just shut off as if you switched the key off, then he phoned back to say engine now running for last 15 mins and not shutting off- arghhh
5) Decided to get Mercruiser dealer to run diagnostic test, he did with no fault codes or issues, he checked the fuel pick up wasn’t blocked says engine running away with no faults and seems to be fine, thinks sea trials required to find fault or breakdown again etc
6) Was down last night, ran engine myself for 20 mins revving etc and purring away nicely – so frustrating

Sorry for the long story but I have lost all faith in her and had the embarrassment to be towed in twice now from the same park rangers, there is clearly something not right and I guess the more information the better so any ideas guys??
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Old 07-26-2009, 11:55 PM   #2
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Default Re: Intermitant Fault with mag 350 MPI

well..more data would help....what sized engine and is it carbed or mpi??....might be either a filthy carb from the statement on filters....or an intermittent bad coil.........but that's only a guess since I'm not there to hear it miss or die..........


welcome to the zoo by the way..

SP :hello:
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Old 07-27-2009, 08:42 PM   #3
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Default Re: Intermitant Fault with mag 350 MPI

Quote:
Originally Posted by seapuppy
well..more data would help....what sized engine and is it carbed or mpi??....might be either a filthy carb from the statement on filters....or an intermittent bad coil.........but that's only a guess since I'm not there to hear it miss or die..........


welcome to the zoo by the way..

SP :hello:
Hi i was thinking there was a clue in the subject header "Re: Intermitant Fault with mag 350 MPI" lol
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Old 07-27-2009, 09:55 PM   #4
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Default Re: Intermitant Fault with mag 350 MPI

DOH!!...i should try and get some caffiene in the morning before I answer these things....dang......



SP
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Old 07-28-2009, 12:56 PM   #5
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Default Re: Intermitant Fault with mag 350 MPI

man..that just sounds strange.....so...places to check in my mind..since no codes showed up.....check the huge plug that connects the engine to the harness....check all connections to the module and computer....make sure they are tight...check the connections to the interrupter switch....then check the connector to the throttle assembly....then there's the switches that your lanyard connects too to shut the engine off..this is an electrical problem and about the only way to find it is to trace everything down.....sorry can't point a finger at it..but these are a real pain..
someone else hopefully will toss a few ideas in here...


SP :hello:
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Don't compare your life to others. You have no idea what their journey is all about.
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------------------------------
2008 Bayliner 340 - "Wild Whim"
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I live in my own little world....but it's okay-they know me here!!!

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Tap-Rack-Bang

Anyone that sez "Size doesn't matter" has never owned a boat!
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Old 07-28-2009, 01:16 PM   #6
Lt. JG
 
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Default Re: Intermitant Fault with mag 350 MPI

Quote:
Originally Posted by seapuppy
man..that just sounds strange.....so...places to check in my mind..since no codes showed up.....check the huge plug that connects the engine to the harness....check all connections to the module and computer....make sure they are tight...check the connections to the interrupter switch....then check the connector to the throttle assembly....then there's the switches that your lanyard connects too to shut the engine off..this is an electrical problem and about the only way to find it is to trace everything down.....sorry can't point a finger at it..but these are a real pain..
someone else hopefully will toss a few ideas in here...


SP :hello:
Hi SP, yes going to have to go over them all with a fine tooth comb, i had a guy on the boat doing a tonage meaurement to do with registering with the shipping act etc, anyway i never met him, his wife phoned asking for access to the boat, she mentioned without keys as long as he could get access to the engine which of course he could, funny problems started after his visit, thinking did he accidently knock a cable or something while he was down there in the engine bay - possible i guess, will keep you posted
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Old 08-11-2009, 09:30 PM   #7
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Default Re: Intermitant Fault with mag 350 MPI

Update - Had the boat out all weekend on the plane giving it plenty, would appear the gremlins have disappeared for now anyway
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Old 08-11-2009, 09:52 PM   #8
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Default Re: Intermitant Fault with mag 350 MPI

well..that's great news....any idea what changed??...


SP irate:
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------------------------
SSN683 Association member
Par Excellence
------------------------------
2008 Bayliner 340 - "Wild Whim"
--------------------------------------
I live in my own little world....but it's okay-they know me here!!!

Avid practitioner of the martial art: KLIK-PAO.
Tap-Rack-Bang

Anyone that sez "Size doesn't matter" has never owned a boat!
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Old 08-17-2009, 08:12 PM   #9
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Default Re: Intermitant Fault with mag 350 MPI

Hi

I have had a similar problem with one of mine 350 MAG MPIs - It was the fuel pressure regulator - wich regulates the fuel pressure and also increases it when vaccum in carb. increases.

Sometimes the engine ran great... but sometimes it smelled a lot of fuel and black smoke, when idleing for a while it died... and was very hard to start. I had to clean the spark plugs... and held the cable from the ignition coil ~aprox. 1 cm above distributor(use gloves and keep your hand high up on the cable fram the dist.

You should also check the vaccum cable when engine running for leaking fuel...

I changed the pressure regulator.. and it ran great - you should also be able to identify this fault by using a fuel pressure meter.. on the rail.

As the fuel pressure regulator is fully passive it won´t show up any fault codes.

Good luck!
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Old 08-17-2009, 08:57 PM   #10
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Default Re: Intermitant Fault with mag 350 MPI

Quote:
Originally Posted by seapuppy
well..that's great news....any idea what changed??...


SP irate:
Still convinced it was dirt in the fuel lines, think maybe its finally been fired through, in reality the only two things that were done were inline fuel filter & water seperator/fuel filter were replaced and the plugs were removed, cleaned and re-gapped
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