2014 Merc 115 WOT problems

[CJ2etc2]

I have a 2014 Harris 220 pontoon w a Mercury 115 outboard I bought a couple of years ago from a lake neighbor when they sold their home. Since I've had it it cuts out and sputters and starts beeping whenever I run it a WOT which considering it's a pontoon I don't do very often. When it does it I cut back on the throttle and it will sometimes again sputter and then run fine as long as I don't run at full throttle. When I reached out to the previous owner to see if he knew what the problem was he said it did happen w him too and they and his shop never figured out what the actual problem was. Ie replaced the plugs and fuel filter before putting it in the water this year and just replaced the fuel line today because it was soft starting to dry rot and I was positive that was the cause but of course it wasn't - did the same thing after running at full throttle for about 45 seconds.

Does anyone have any idea what could be causing this problem?

Thanks for any help!!

Craig

 

[QBhoy]

Hi. One of two things.
If it’s happening at close to or full throttle, there is a good chance it’s the rpm limiter. This will beep at a certain rpm and cut the ignition like a miss firing effect.
This would be caused (common on a set up like yours) by the engine rpm limiter being easily reached, as a result of the prop venting due to a poor engine height set up (common on pontoons and from what I gather. Almost unavoidable occasionally)…or the prop pitch being too little, meaning it easily over revs. Quite common when a less than adequately powered engine, for the boat, is propped to try and compensate such a thing.

Other possibility that would be favourite for such a thing…is that the engine has lost water pick up and overheating. This too caused by a poor engine height set up. Again..a common thing on these type of boats.
I’m not a man familiar with such boats, but I’m very aware of the symptoms perhaps. Someone with more experience on these things, will undoubtedly be able to advise, agree or disagree perhaps.
All the best.

 

[CJ2etc2]

Hi. One of two things.
If it’s happening at close to or full throttle, there is a good chance it’s the rpm limiter. This will beep at a certain rpm and cut the ignition like a miss firing effect.
This would be caused (common on a set up like yours) by the engine rpm limiter being easily reached, as a result of the prop venting due to a poor engine height set up (common on pontoons and from what I gather. Almost unavoidable occasionally)…or the prop pitch being too little, meaning it easily over revs. Quite common when a less than adequately powered engine, for the boat, is propped to try and compensate such a thing.

Other possibility that would be favourite for such a thing…is that the engine has lost water pick up and overheating. This too caused by a poor engine height set up. Again..a common thing on these type of boats.
I’m not a man familiar with such boats, but I’m very aware of the symptoms perhaps. Someone with more experience on these things, will undoubtedly be able to advise, agree or disagree perhaps.
All the best.

Unfortunately that makes a lot of sense. This engine sits lower in the water than any other I’ve ever seen - water is to just below the water tube. Is that what you mean or that the boat is too big for the 115hp? What is a/the solution? Thx

 

[QBhoy]

Unfortunately that makes a lot of sense. This engine sits lower in the water than any other I’ve ever seen - water is to just below the water tube. Is that what you mean or that the boat is too big for the 115hp? What is a/the solution? Thx

I was more meaning that the engine may be too high and gulping air into the water intakes on the side of the gearbox.
Given what you’ve said..it’s now quite likely that you may be hitting the rpm limiter perhaps. What rpm are you seeing at full throttle ? Is this one of the newer 2.1l merc 115 or the older 1.8l merc 115 ? Just to we get the proper rpm range you should be in. Not sure what the 1.8l engine runs to…but for example, I know that the 2015 onwards 2.1 litre engine had a rpm range of 5000-6000 rpm and will electronically limit the rpms at about 6100ish rpm and cut the ignition.
What rpms and speed does this happen at with you ?

 

[CJ2etc2]

I was more meaning that the engine may be too high and gulping air into the water intakes on the side of the gearbox.
Given what you’ve said..it’s now quite likely that you may be hitting the rpm limiter perhaps. What rpm are you seeing at full throttle ? Is this one of the newer 2.1l merc 115 or the older 1.8l merc 115 ? Just to we get the proper rpm range you should be in. Not sure what the 1.8l engine runs to…but for example, I know that the 2015 onwards 2.1 litre engine had a rpm range of 5000-6000 rpm and will electronically limit the rpms at about 6100ish rpm and cut the ignition.
What rpms and speed does this happen at with you ?

Not sure on 1.8 vs 2.1 but the problem happens around 4500 rpm

 

[QBhoy]

Not sure on 1.8 vs 2.1 but the problem happens around 4500 rpm

Ok. That’s certainly below the limiter then.
I’d now be inclined to check a few other things. Start with the oil level in the engine.
Then go to look at the sensors associated or that can be affected by the throttle movement, when things go wrong. These would be things like the neutral safety switch getting nudged inside the remote control box. Or the shift switch under the cover of the engine, near the throttle and gear cables, as they enter. If yours has one. That is.
If you are at all unsure…please go and see a marine engineer who can plug the diagnostics in.
Final thing from me…are you on plane when this happens ? If so, are you sure that the water intakes on the lower unit aren’t taking air in, when on plane ?