MickMercury
New member
2001 Mercury 90 ELPTO two stroke.
I have a problem of many years intermittently, where the motor runs fine for 5-10 minutes then drops speed then kicks back in and runs fine all day, going out to islands (15-20 km) and snorkelling in different locations. Originally the problem could sometimes be driven through, then you had to stop and idle or shut down completely, start again and off we’d go.
3 mechanics have checked it out, it’s been serviced more than once with the issue in mind.
Fuel has been drained and replaced, hoses from filter to engine replaced, new plugs new filters, alternate fuel source used, carbies striped and cleaned more than once. New coils, trigger changed.
Rimfire plugs have been changed to normal plugs but there has been no difference.
The problem is more regular now since a concerted effort to solve it. You can take off do over 5000rpm flat out (normally I run at 4100) and it will drop back to 4000 rpm (reduces by 1000rpm). It farts like it’s missing but it’s actually firing and trying to go. Then it will free itself after 5-10 mins and fire fully on all 3 cylinders. It seems like a blockage has cleared then you are all set to go for the day.
Mercury service person who has serviced it said as its an older in age motor and it would cost a lot to pull apart it’s probably not worth it. He seems to think it’s a problem inside the motor like a corrosion or a blown crankcase gasket.
Compression test was apparently OK.
The motor has 475 hours. It has not been run on ethanol fuel.
Thanks for any suggestions as to what to look for.
I have a problem of many years intermittently, where the motor runs fine for 5-10 minutes then drops speed then kicks back in and runs fine all day, going out to islands (15-20 km) and snorkelling in different locations. Originally the problem could sometimes be driven through, then you had to stop and idle or shut down completely, start again and off we’d go.
3 mechanics have checked it out, it’s been serviced more than once with the issue in mind.
Fuel has been drained and replaced, hoses from filter to engine replaced, new plugs new filters, alternate fuel source used, carbies striped and cleaned more than once. New coils, trigger changed.
Rimfire plugs have been changed to normal plugs but there has been no difference.
The problem is more regular now since a concerted effort to solve it. You can take off do over 5000rpm flat out (normally I run at 4100) and it will drop back to 4000 rpm (reduces by 1000rpm). It farts like it’s missing but it’s actually firing and trying to go. Then it will free itself after 5-10 mins and fire fully on all 3 cylinders. It seems like a blockage has cleared then you are all set to go for the day.
Mercury service person who has serviced it said as its an older in age motor and it would cost a lot to pull apart it’s probably not worth it. He seems to think it’s a problem inside the motor like a corrosion or a blown crankcase gasket.
Compression test was apparently OK.
The motor has 475 hours. It has not been run on ethanol fuel.
Thanks for any suggestions as to what to look for.