90 H.P Mercury 4 stroke 2006 NEED HELP

Motor started cutting out on last trip of last year. Took the boat out yesterday for 1st time this season. When I first got up on plane it began to cut out (fully expected) it would come and go like a fuel supply issue. Fished with trolling motor most of the day. When getting ready to leave the lake the motor wouldn’t take off at all. Runs fine at idle. Sounds good if I rev it up in neutral, but when the motor is placed under a load it has very little power. Fuel line was replaced a year or two ago.

Any ideas for me to try?

Holdem

Fuel filter

Fuel line

Check the fuel line connection at the motor

I have a 75 hp 2007 that did that. ended up being the fuel supply module. the float gets gummed up from old gas .needs replacing.

Robb McMahon wrote:

Motor started cutting out on last trip of last year. Took the boat out yesterday for 1st time this season. When I first got up on plane it began to cut out (fully expected) it would come and go like a fuel supply issue. Fished with trolling motor most of the day. When getting ready to leave the lake the motor wouldn’t take off at all. Runs fine at idle. Sounds good if I rev it up in neutral, but when the motor is placed under a load it has very little power. Fuel line was replaced a year or two ago.

Any ideas for me to try?

Holdem

I have a 2007 Merc 60hp (basic same engine) It showed the same symptoms. Mine was still under warranty. Took it in, dealer hooked it up and discovered a bad ignition coil. (each cylinder has it’s own coil on this motor) Replaced the coil and everything was fine.

Had the gaskets in the fuel pump go bad on me once. But was slightly older motor

Huntindave wrote:

<div class=”d4p-bbt-quote-title”>Robb McMahon wrote:</div>
Motor started cutting out on last trip of last year. Took the boat out yesterday for 1st time this season. When I first got up on plane it began to cut out (fully expected) it would come and go like a fuel supply issue. Fished with trolling motor most of the day. When getting ready to leave the lake the motor wouldn’t take off at all. Runs fine at idle. Sounds good if I rev it up in neutral, but when the motor is placed under a load it has very little power. Fuel line was replaced a year or two ago.

Any ideas for me to try?

Holdem

I have a 2007 Merc 60hp (basic same engine) It showed the same symptoms. Mine was still under warranty. Took it in, dealer hooked it up and discovered a bad ignition coil. (each cylinder has it’s own coil on this motor) Replaced the coil and everything was fine.

I had the same issue last summer, replaced fuel line, it was collapsing internally and had to replace a coil. Coils tested fine with the recommended tests- but one plug not getting spark every time. Weak coil.

Change the spark plugs. A bad plug will sometimes fire until you put a load on it. Easy fix if thats the problem. If not you got new plugs anyway.

When it does that try choking the motor; if it comes back, I’d bet on dirty carbs / plugged high speed jet.

Huntindave wrote:

<div class=”d4p-bbt-quote-title”>Robb McMahon wrote:</div>
Motor started cutting out on last trip of last year. Took the boat out yesterday for 1st time this season. When I first got up on plane it began to cut out (fully expected) it would come and go like a fuel supply issue. Fished with trolling motor most of the day. When getting ready to leave the lake the motor wouldn’t take off at all. Runs fine at idle. Sounds good if I rev it up in neutral, but when the motor is placed under a load it has very little power. Fuel line was replaced a year or two ago.

Any ideas for me to try?

Holdem

I have a 2007 Merc 60hp (basic same engine) It showed the same symptoms. Mine was still under warranty. Took it in, dealer hooked it up and discovered a bad ignition coil. (each cylinder has it’s own coil on this motor) Replaced the coil and everything was fine.

Not the same motor, but the same symptom was the same problem (bad coil) on a motor I owned. It was explained to me that when they are failing the heat from a warm engine can cause them to fail intermittently. I believe it can be difficult to diagnose which coil is bad if this is the case because it is intermittent. I replaced all three coils on my engine at the time and it was good to go.

I do wonder if you have the same problem here if it wouldn’t take off at all at the end of the day. Maybe try it again with a cold engine. Or, if the coil failed completely and you’re down a cylinder, if I recall correctly you can use an ohm meter to check the coils as an initial matter.

If you’re not careful you can end up throwing a lot of parts at an engine in this situation. I’ve learned the hard way that a good mechanic can be cheaper.

Fuel, spark, or air leak.

I had a similar issue with a Johnson/Evinrude. Mine was air-related.

I replaced plugs, plug wires, checked coils, replaced fuel line, cleaned fuel filter, replaced ball, and replaced tank pick-up. There’s a plastic housing which the carburetors mount into. It attaches to an aluminum section of the engine block. In between is a rubber gasket, which was leaking. The plastic bracket was also warped and needed to be replaced. Fixed the issue, but wasn’t cheap.

Thank you all for taking the time and throwing out some possible causes to my issue. I’ll see what I can find…

Robb