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Old 15 August 2016, 02:01   #1
rnwright1969's Avatar
Country: UK - England
Town: Darlington
Boat name: Duo-diver
Make: Avon SR5.4
Length: 5m +
Engine: Mariner 90hp
Join Date: Nov 2013
Posts: 18
An odd-ball engine problem!

I was having a pootle at the weekend and had a strange problem with my old 2 stroke, 90hp mariner clam-shell.......said motor is set up with an hour meter, a trim gauge and a rev counter and, touch wood' had never missed a beat.

As usual I ran the rig up on a set of mufflers to make sure everything was hunky dory and it was, started first turn and good flow of water through the tell tale.

Out at sea about 3 miles into the cruise there was a sudden loss of power and the engine wouldn't rev, 'ahhh thinks I a carb issue, dirt or blocked nozzle', maybe two minutes later everything great and off we go, again

Blast up to Holy Island so about 15 miles, touch of lunch and off home again, about 0.5 miles out I get what sounds like a oil alarm.....'engine off, checked and its at three quarters', engine on and away we go about 2 miles further on the trim goes full scale deflection as if the engine is 'lifted' and the rev counter sticks at 3800rpm, well with the current frau wright on board I don't hammer it.

Switch off the engine/ignition and restart and she fires straight up and away we go, this happened another twice on the way back home!

My good friend the ancient diver thinks a short circuit somewhere, potentially in the throttle assembly, I had a full service with all manner of new looms etc at the start of the season by a well known NE chandlers, any ideas and/or suggestions of a good Northumberland/Borders based marine electrician as I want a second battery and changeover switch fitted anyway!

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Old 20 August 2016, 07:01   #2
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,538
Certainly sounds like a rogue short or possibly an intermittent earth failure. A bit like on old cars where an earth fault on the tail light cluster gives a nice set of disco lights as the power earths vis other bulbs.

One question. Clamshell. ... oil 3/4 full.... clamshell never got auto mixing unless you have an oil mixer on your transom?

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Old 21 August 2016, 04:05   #3
Country: UK - England
Town: Leicester
Length: 5m +
Engine: 135hp Mercury
Join Date: Sep 2013
Posts: 558
Parts list for a clamshell 90 - I've just picked it at random from several options on the site - shows oil injection components.
1989 Mariner Outboard 90 [ELPTO] [70904129C] - Parts Lookup - Crowley Marine
OIL INJECTION COMPONENTS SECTION - 1989 Mariner Outboard 90 [ELPTO] [70904129C] - Crowley Marine
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Old 21 August 2016, 05:46   #4
Country: UK - England
Town: bicester
Length: no boat
Engine: outboard only
Join Date: Feb 2009
Posts: 851
If that was me I would go and check all my earths , make sure that they are clean, bright and tight, check the plug/socket on the main wiring loom,look inside the socket to make sure there is no sea water corrosion inside I have seen that problem before ,are the pins clean and making good contact?
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