2016 Mercury 115HP 4 stroke

by Todd Kennedy
(Lexington, NC)

After 30 or so minutes running around 3000 - 4000 RMP I get a miss in the engine. This miss only starts after 2600 RPM so if I stay under that there is no issue. I have replaced the entire fuel system and replaced the ignition coils and still have the same issue.

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Aug 09, 2021
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by: Wayne M. Breeden

Our problems will almost always be at 1.1 hours of running at about 3550 RPM. At that point we get a sudden reduction in power with some surging. My wife has on many occasions refused to get back on board due to the problem. This has ruined our boating pleasure!
I replaced the crankshaft position sensor twice at a $100 each. I have unplugged all of the sensors and computer, cleaned the connections with CRC contact cleaner, run with the cowling off to air-cool the electronics, sucked all of the fuel out of the tank and checked the filter. We spend most of the time on a major waterway with heavy line boat cargo barges. I do not want to get run over or swim out of the way while watching my boat being crushed!

We left the boat with the dealer/service center for ten months while under warranty. They could never duplicate the problem because it was tested on a cooling hose in the lot with the cowling off running with no load. (I told them this would not work) Mercury just wants the service centers to deal with the problems of these motors and will not communicate with the owner. Most shops have told me three to eight months before they get a look at it in the shop and will not run it in the river. I have a Vessel View system but it indicates no faults with the failure incidents.

In short, Mercury service centers are independent and the manufacturer seems not to hold them to a standard of accountability.
Based on my experience, and reading of other similar problems. Mercury warranty is worth nothing and support is pathetic. So much to be said about my patriotic attempt to "buy USA goods".

My layman, owner analysis, is at this point, the computer and sensor package under the cowling is probably heat or time sensitive and puts the motor into "Guardian/Protect mode" based on a phantom problem. I have considered adding a cooling air fan to blow cool, fresh air through the cowling. By design, the only airflow the electronics get under the cowling is sucked into the induction for combustion.

I suspect these issues are predominantly manifested in the warmer climates in the southern USA, not the northern location of the manufacturing and testing facility.

I just want Mercury to acknowledge the problem and come up with a fix that I can comply with.

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