Paul J Posted September 29, 2013 Report Share Posted September 29, 2013 Hi Gents I'd like to pick your brains and would welcome suggestions on what the problem could be and where to look. The problem is on my mates 1998 mariner 4 stroke 25hp bigfoot outboard. It starts fine and runs sweet for about an hour and then fails to start, leave it for an hour and it starts up again with no problems. Last time we were out we ran for about 10 mins then went on the drift, starting up the engine several times to redo the drift- not big distances traveled and not enough to get the engine hot( imo). After an hour or so of doing these small drifts the engine turned over but would not fire! we ended up paddling the boat to the slip way which took about an hour. I tried to start it again as my mate went to get the trailer and it started after laboring a bit and ran fine at idle- we didn't want to risk going out again. It s very frustrating as it seems intermittent and it takes a lot of time and effort to recreate the problem. Anyone have any idea what this could be? All suggestions very welcome Cheers PJ Quote Link to comment Share on other sites More sharing options...
Coddy Posted September 29, 2013 Report Share Posted September 29, 2013 Hi Paul Have a look at the fuel pump diaphragm as it might have an air leak as it heats up, also that the fuel line &/or prime bulb is ok, don't forget the one way valve in the primer. if none of the above I would suggest a strip down and clean the carbs & jets as it seems to be a fuel issue. Just had another thought, check the fuel pick up pipe is not kinked in the tank Dave Paul J 1 Quote Link to comment Share on other sites More sharing options...
Coddy Posted September 29, 2013 Report Share Posted September 29, 2013 Hi Paul again Had another thought, might be worth getting a compression test done. There was a problem with some Mercury/Mariner engines where the head gasket restricted water through the engine. I had this problem on my Mariner engine on Sammy, the Warrior 165, it turns out that it was a common problem. Just maybe the head gasket is leaking between the seals under the head/gearbox faces. Just a thought Dave Paul J 1 Quote Link to comment Share on other sites More sharing options...
Brian Posted September 29, 2013 Report Share Posted September 29, 2013 Could be an ignition component overheating. Had same symptoms with my previous boat, Volvo petrol inboard. I traced it to a faulty condenser in the distributor, the ignition coil got hot and engine died, let it cool down for 10 mins and ok for another 30 to 40 mins. Paul J 1 Quote Link to comment Share on other sites More sharing options...
Jim Posted September 29, 2013 Report Share Posted September 29, 2013 I had similar on an old Mercury Blue band. Ran great for a few hours and then it would not start. Next day, it would start easy. I fixed and checked a load of stuff but in the end my feeling was the coils ( or component parts ) were breaking down and heat build up was causing my grief ! Jim Paul J 1 Quote Link to comment Share on other sites More sharing options...
ChrisE Posted September 30, 2013 Report Share Posted September 30, 2013 I'm sure that you will have checked for water in the fuel. We had a similar problem, which we thought was down to engine getting hot, but in fact was due to fuel being bounced around whilst travelling and being sucked into the fuel line. Paul J 1 Quote Link to comment Share on other sites More sharing options...
Paul J Posted September 30, 2013 Author Report Share Posted September 30, 2013 Thanks for the input guys, really usfeul stuff here, i'll let you know if we find the problem. In the meantime, If there are any other suggestions keep them coming as it could be helping someone else also Cheers PJ Quote Link to comment Share on other sites More sharing options...
Rob Posted September 30, 2013 Report Share Posted September 30, 2013 Vent hole on tank blocked? Need to check the 3 magic things on starting, spark, fuel and air. R Paul J 1 Quote Link to comment Share on other sites More sharing options...
Rob Posted September 30, 2013 Report Share Posted September 30, 2013 Vapour Lock: http://en.wikipedia.org/wiki/Vapor_lock Paul J 1 Quote Link to comment Share on other sites More sharing options...
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