Alarm and Limp Mode

[skram]

Out on the St Lawrence river Friday (about 2 hours running at 3500 - 4000 RPM )and just about back at marina running about 4500 RPM and suddenly beeping from motor (2017 Merc 4 Stroke 115hp about 30 hours on it) and then limp mode. Slowed, moved towards bank and placed in idle. After a few minutes motor running smooth and started out. No problems, took it up to 4500 RPM again, no problem, continued back to marina and smooth running same as before alarm. Assumed picked up some weeds ( had moved across a weedy area shortly before the alarm) Yesterday went to the marina and ran hose to engine flush tube and let run through for 10 minutes or so. Haven't been out since so no update. Called where we bought the boat (new in 2017) and mechanic said probably picked up weeds and not to worry unless it happens again, then need to look at motor, maybe code generated that would indicate. Should I worry, anything else I should do. Thanks in advance for any info.

[Moser]

30 hours is not a lot of hours, but 3 years is a reasonably long time for oan impeller to be in, especially if it has not been run much. If it does not alarm next time out, I'd leave it alone , but schedule an impeller change in the off season.

Impellers that sit, take the shape of the inside of the pump, which is offset, so they are conpressed further on one side than the other. When you use them then, the compressed fins do not spring back far enough to effectively seal the wide side of the pump housing and the flow is diminished. It could be fine for 3 more years, but I would change theat impeller in the off season.

I did not use my Sea Nymph at all last yar, but I am going to, at the end of August, I will change the 4 year old impeller before I use it, it is 2 hours and 30 dollars, cheap insurance to me.

[skram]

Thanks Moser, thought that with lower hours would be ahead on maintenance like this. Will see how we do next outing and take it from there, definately on the end of season list now.

[skram]

Went out today, no alarms smooth run. Manual confirms impellar 3yrs or 300 hrs. Anyone gone further either hours or years with no change? I plan to change it this fall with wnterization.

[Moser]

I'm glad she ran good for you today, you wshould be good until fall.

In typical mechanic fashion, I will confess to having gone way over the recommendations, but no more. I have destroyed a nice V4 OMC by getting it hot. I have a 9.9 Johnny here now that got hot and will need rings. Make sure your alarms work and don't run with the alarm sounding.

My new rule for impellers is every 3 years, and on new used engines, if you don't KNOW when iit was changed last, it is time to change it now.

[FogHorn]

I had mystery overheats on my previous boat which I suspect on one occasion was a plastic bag someone had trashed into the river (found as it floated-up when I halted and shut-down to investigate.).

On another event, found a “ball” of clay loosely bobbing around at the inlet to the sea-water strainer. (Volvo heat-exchanger used sea-water to cool a closed-system. The heat-exchanger is equipped with a strainer-cup.)

Those two events were lucky finds but it causes me to recollect them when I read about “mystery” overheats.