Hi all.
A friend just bought a new to him boat with a mariner magnum 150 v6. Same as the merc 150 v6 2 stroke. Will likely be an early 90’s thing.
At idle it has higher rpm than it should. First thing I noticed, so it’s quite violent going into gear. At a guess it will be doing about 1200 rpm or close to each side of that. So thought no big deal..just needs an adjustment. But then after warming it up at the slipway. We head up the river. At its idle speed when in gear and even a little higher than idle...it almost sounds as if it’s missing or dropping its ignition on a cylinder or two. Very smokey (much more than it should be and mix is correct). Take it out of gear and the rpm shoots up again. Into gear it’s very low and almost cutting out and missing or rough sounding.
I’m now thinking that the previous owner has adjusted the idle speed to try and counter another issue that causes the low rpm in gear at idle.
The owner has changed the plugs but no difference. If it was a different engine with an alpha, I’d almost swear the shift interrupter switch was being activated when it’s in gear. If you get what I mean.
Sounds lovely at higher rpm and plenty of power when throttle opened.
Compression all good and around 115-120 on them all.
Any pointers ? Thanks.
A friend just bought a new to him boat with a mariner magnum 150 v6. Same as the merc 150 v6 2 stroke. Will likely be an early 90’s thing.
At idle it has higher rpm than it should. First thing I noticed, so it’s quite violent going into gear. At a guess it will be doing about 1200 rpm or close to each side of that. So thought no big deal..just needs an adjustment. But then after warming it up at the slipway. We head up the river. At its idle speed when in gear and even a little higher than idle...it almost sounds as if it’s missing or dropping its ignition on a cylinder or two. Very smokey (much more than it should be and mix is correct). Take it out of gear and the rpm shoots up again. Into gear it’s very low and almost cutting out and missing or rough sounding.
I’m now thinking that the previous owner has adjusted the idle speed to try and counter another issue that causes the low rpm in gear at idle.
The owner has changed the plugs but no difference. If it was a different engine with an alpha, I’d almost swear the shift interrupter switch was being activated when it’s in gear. If you get what I mean.
Sounds lovely at higher rpm and plenty of power when throttle opened.
Compression all good and around 115-120 on them all.
Any pointers ? Thanks.
