2002 Mariner 60hp 4st running very rough at 2500rpm

[McFish]

Guys, I have a 2002 Mariner 60hp 4 stroke which is running very rough on load at about 2500rpm, it will sometimes jump through this and everything then seems ok but yesterday it will not go past about 2000rpm and is very erratic/drops rpm very quickly if you try to push past 2000 rpm. It has had new plugs, filters, oil, has a water seperator fitted to fuel line. I ran engine dry of fuel and drained carbs as much as i could in the hope that it may have been drop of water in card but no different. It seems like the engine is limiting itself for a reason but plenty of water cooling as i had a cooling issue last year and had a rubber grommit replaced in the cooling systems which was suppressing water flow, i now have great water pressure, engine doesnt feel overl;y hot but i have no temp gauge. Any ideas?

 

[McFish]

Re: 2002 Mariner 60hp 4st running very rough at 2500rpm

Hi Guys, i have just got this engine back from the garage. They diagnosed carb problem on no 4 carb so stripped it and cleaned it. They also did a compression test and found poor compression on 3 of the 4 cylinders (<100 psi). There was also water in the gear oil which is a new one on me as i have never seen any water in oil when changing it. I was told that all the ignition electrics were tested, plug leads, stator, coils at idle but no faults detected. Finally they did a synch on the carbs and were happy they had addressed the rough idle and the poblems at 2500 rpm on lift off. I water tested it myself yesterday and unfortunately the problems have not been solved at all. The engine is still running very rough at 2500 RPM but will push through it most times and runs fine above this to 5000 rpm and 30 knots. On the odd occasion that it didnt push through 2500rpm it was erratic and cut out completelty a few times. Any help would be much appreciated as i cant afford to get too much more time spent on this without an improvement in performance.

 

[McFish]

Re: Rough Mid Range on2002 Mariner 60hp 4st

Re: Rough Mid Range on2002 Mariner 60hp 4st

Anyone with similar experiences on any make of engine please send reply, could this be stator, coil problems. I will test the primer bulb when under load at 2500 rpm next day just to make double sure this is not a fuel issue, as i said in previous post the carbs have been cleaned and synched and i dont see where the fuel issue could be coming into it after all the work done so far. She is bogging down from about 2300-3200rpm and picks up only if forces through on throttle.