2000 Tohatsu 115 two stroke problem

This is a new boat and motor to me. I took this boat on its first trip and everything seemed to run fine. Only when I would go to accelerate the tach buzzer alarm would go off for a second or two and then the boat would accelerate. I was able to get up to 3700 r.p.m.'s. I tried using it today and could only get the boat to go up to 2500 r.p.m's. At that point the alarm would come on and some kind of limiter would prevent me from going any higher in the rpm's. As soon as I dropped the rpm's to 2400 the boat was fine. Any idea's what this is?

I'm not sure whether you have an A or A2 model, but if you have an M115A2 model, see the description of alarms on page 39 of your owner's manual. You can download a copy of your owner's manual at http://www.tohatsu.com/tech_info/own_man_pdfs/Toh115A2.pdf

You are probably not pumping cooling water adequately. Is the telltale flowing? When was the water pump last serviced? Are you getting any indicator light warnings on the tach?

Ideally, you should be able to hit approximately 5500 RPM, give or take about 200 RPM. Once you resolve the alarm condition, if you still can only go about 3700, you may need a tune-up or a different prop.

The tell tale is flowing great. I did not see any warning lights on the tach, but i will check tomorrow when I use the boat.

I had a Yamaha that did the same thing when the oil got below a certain level. Could that be the issue?

As far as the owners manual I did see where they listed 2800 as the max. rpm if there was a blockage. This is close to the rpm I am stuck at. It said there was a water flow sensor that monitors the flow of water and holds the engine at this rpm's if there is a flow problem.

Where is the sensor located? In the lower unit or up top in the block?


(The hull is a displacement hull, so I am not sure about max rpm, but 3700 does seem low, where it should be around the rpm you mentioned.)

Yes, there is a low oil sensor as well. See that same page of the manual. The water pressure sensor is on the powerhead. If you want full details, grab a Factory service manual, available from any dealer, including me.