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Outboard motor won’t accelerate past 1800 rpm

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Curtis D Petersen

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I have a 2018 Bennington 23 R with a 2018 115 HP Yamaha SHO and I’m having trouble figuring out why it won’t accelerate past 1800 RPM. I was pulling my granddaughter tubing at full speed and all of a sudden the speed dropped to 1800 RPM. The throttle was still wide open. It allowed us to limp home but still won’t go past 1800 RMP. I put new plugs in it, didn’t help. I took it to a marina and they put inline fuel filter, spin on fuel filter and new bulb and fuel lines. They said they were corroded and had “rust” in them. They thought that fixed the problem but when I put it back in yesterday the problem still exist. Has anyone else had a similar situation and might know what to look for?

Curt Petersen
 
So no motor beeps, alarms or codes?
 
That may help narrow a bit of the options out, especially for our more mechanically knowledgeable members. With it being sudden, in my mind, that seems to make some options also less likely: say leaking pontoon with water in it, something of that nature. If you had hit something with pontoons or prop, you’d probably know. I am assuming the prop looks good, doesn’t spin, etc, etc…

I wonder if maybe something went sideways with the impeller? Do you know how old that is? Our neighbors pontoon recently all of a sudden dogged out. Elderly gentleman. Come to find out they had never had their impeller changed. It was original from 2019, and we have a more sandy but shallow lake. He went in thinking prop or hub, or bad gas…ended up being the impeller.

That said, impeller/lower unit repairs are pricey, so not something to just do to see if it works in case it’s something else, and something easier or more cost effective.
 
Plus 1 on the impeller
 
Have you checked your fuel injectors ? If you have rust in your lines it could be clogging your injectors.
 
I got the marina to send a couple service technicians to the lake today and they think now it might be the ECM (electronic control module) or the wiring to the ECM. They said it is not allowing the throat body to open all the way. ‍♂️ It’s not the prop and they had checked the compression in all four cylinders earlier and those were all good. Does this sound like it could be a reasonable explanation? Maybe the ECM is Engine Control Module not Electronic Control Module
 
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Seems to be in Limp mode for a possible couple of reasons. Low oil flow, overheat, or maybe a bad sensor. Does the motor shake when you hit the 1800rpms? Could be a dead cylinder because of a coil, bad stator. I know you changed fuel filters, but what about a clogged VST or anti siphon valve? Could be starving the motor of fuel?

Keep us updated on what your techs find.
 
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