Momentary loss of RPMs

[dhylander]

Hello everyone,
Was out on the lake yesterday for about 90 minutes with no issues, then as I was heading back to the marina I had a few instances where the RMPs dropped monetarily on the port engine to about 5500. Once when I was running at 6500 RPMs and another time while running at about 7200 RPMs. There was a difference in the engine sound when the RPMs dropped. Then when I got into the marina area and engaged the no-wake mode the engine overheat light came on for the port engine as well. I shutdown the port engine and when I restarted it the overheat warning light went away. I am getting water through the pitot tubes. Any ideas of what is going on? Thanks.

 

[anmut]

Check your pump and water pickup screen for debris.

 

[WREKS]

@dhylander Water from the rear pilot tubes indicate that the thermostats are open. As for overheating, I try to keep three feet of water under the keel. Boating in shallow water can lead to overheating problems.

 

[haknslash]

I assume he is talking about the pissers on the side of the hull and not the tstat hole above the jet pump.

As mentioned check for any debris that may be inside the jet pump. There is a small white screen that can sometimes have debris cover it up and cause issues. That screen is the inlet for the boats cooling system.

 

[David Martin]

I agree checking for debris, also I just installed temp gauges on my engines and noticed, as I was returning to dock in rough water, with wind to stern , tide running out, I kept sucking air into port engine when I dropped to no wake mode the port engine went up 20 degrees over starboard, both temps went up for a few min.

 

[tdonoughue]

I just installed temp gauges on my engines and ....

Not to get too off topic here (and maybe you can post to a new thread), but I would be very interested in what kind of temp gauge you installed and how you did it. Thanks.

 

[dhylander]

Thanks everyone, I'll try checking the screens and let y'all know how it goes.

 

[212s]

Thanks everyone, I'll try checking the screens and let y'all know how it goes.

I concur with the others...sounds like a blockage. If you see some gunk on the screens just remember they're plastic so don't get crazy poking at it or using too harsh of a cleaner.

 

[Scottintexas]

the quirkiness of a Yamaha,

my guess would be you sucked something up, a twig, bottle cap, weeds, but it didn't go through the impellers,

when you went to no-wake it was enough disturbance to effect cooling water flow,

when you turned the engine off whatever floated/was pushed out the the intake and when you started back up, no issues,

many times we see this when people take the boat out of the water, the problem magically goes away as the debris falls out when the boat is loaded on the trailer,

personally I wouldn't even give it a second thought unless the problem happened again,

it's a good idea to always do a walk around and know where to look for stuff so I'd tell you to do it at this point just to be familiar with your boat, also
there is a video in our FAQ about "how the cooling water flows in MR1" it's not your engine but the concept is the same and it's a great way to understand your boat/cooling water/engines


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