Mariner 60 Hp Bigfoot problem

[jonjonC]

I was 6 miles from port recently when the engine, which has always worked perfectly before, decided to play up. However much throttle I applied, the revs would not go above 2,500 and the boat would only manage 6 knots. Turned for home and did 20 minutes of limping when the engine sprang to life again and we got up onto the plane. Just outside the marina the problem occured again and is now present. When not in gear the engine will rev to 4,500+ as normal.
Any ideas as to what might be wrong or what to check first?

[jyasaki]

4-stroke? Sounds like it's going into guardian mode, which cuts the revs back to prevent the motor from eating itself.

Make sure the tell-tale is telling. Overheat can do that. Check oil level and, if possible, pressure (if you have gauges, there should be an oil pressure idiot light.)

Worst case is to take it to a mechanic and let them figure out what's triggering it.

jky

[TUFTY]

Had very similar experience with 2 stroke 3 cylinder 60hp Yamaha.

Problem was dirty / old fuel causing blocked jets in Carbs.

Removed and cleaned all 3 carbs, Fresh Fuel used, Problem solved.


Hope this helps?


Paul

[al40]

If it's not the ECU cutting the engine power (assuming it has an ECU) then could be one of several other things:

- Dirt in carbs as per tufty's suggestion
- Blocked fuel filter
- Fouled plugs
- other Electrical fault (dodgy plug, spark plug lead or coil).


At rest it will rev happily with most faults as there is no load (and would probably happily run on one cylinder).

Most times I've seen this issue it's been either fouled plugs or dirt in carbs. Would be worth pulling the plugs to have a look or if they are old, replace them.

[Turbodiesel]

2 stroke or 4 stroke?,

If its a 2 stroke it sounds like a carb playing up.

[9D280]

As Al says, pul lthe plugs. If it;s a 2- stroke the dirty one will tell you which cylinder to look at more closely.

[jonjonC]

What a response!!!
Many thanks for all the ideas.
I've ordered new plugs and fuel filter and will fit them as soon as possible. And if I can find the carbs I'll flush them out and get new petrol before going for a test run.
I've only just found this site but you can bet I'll be a regular visitor from now on.
(By the way, the engine's a 2-stroke --- can't afford a 4.)
Thanks again and I'll post a reply when I've done the test.

[andy9466]

i had a similar problem with my 75hp it turned out to one of my cdm modules (ignition coil to look at) hope this helps
andy

[jonjonC]

Many thanks to everyone who replied to this query.
Yesterday pm replaced the plugs, drained the carbs and replaced the in-line fuel filter. Took her out for a spin in a much-too-big sea but, whilst scaring myself sh*tless, managed to accelerate smoothly and onto the plane, achieving 14 knots before yellow-striping it back home.
Job done.
I really appreciate the advice - it worked like a charm. Now looking forward to the next trip.