Have Boat Questions? Ask a Boat Repair Expert.
Do you have a tachometer on the boat? What warning light illuminates?
Is it a Yamaha gauge?
Have you checked the oil level? It sounds like the engine is in guardian mode where it cuts the rpm back if the engine runs low on oil, low oil pressure or is running hot. The Yamaha gage has diagnostic/warning lights, which I am asking which tach.
In the future you may want to have a Yamaha gage installed.
Is the oil level above the full mark at all?
OK is would appear you are what is called "making oil". Fuel is getting into the crankcase, quiet often particularly pontoon boats or boats used for alot of idling or trolling. This problem can cause low oil pressure. I'd bet if you smell the dipstick it will smell like gas.
What you need to do is drain and refill the oil and change the oil filter. This will raise the oil pressure. The gas in the oil dilutes the oil.
Yamaha recommends the use of Ring Free in the fuel to help keep deposits down and help prevent ring sticking on the pistons allowing the fuel past the piston rings.
Try this and post back your results.
Sure just post back at your leisure. I'll be in and out tomorrow but will respond as soon as I can.
Change the filter too!
Did you get the oil changed?
Does the alarm still go off? How long did you run the engine with the noise?The crankcase oil is in the crosshatch marks of the dipstick?
Do you happen to have a mechanical (car type) oil pressure gauge. If not you can borrow or rent one from an auto parts store. Put it in place of the oil sender and see what the pressure is.
You need to get an oil pressure gauge. Remove the sender and put the gauge in the port and then crank the engine. Remove the spark plugs so it will crank easier and also not start. See if you are getting oil pressure. It's possible the oil pump is faulty.