All,
Picked up a tinnie fitted with a Yamaha 25HP a couple of weeks ago and took it for its maiden voyage yesterday. Ended up having a problem, however firstly by the look of the plate on the engine, I "thinK" the model number is a 61_2? The guy who sold it to me, said it was only a few years old with less than 50 hours use. Its looks in tip top condition and is clean as a whistle.
Anyways the problem:
Left Berowra Waters ramp, motored down the channel at 4 knots which took about 10 or so minutes:
Once clearing the 4 Knot zone, opened the throttle and it took off without missing a beat. Throttle was about 1/4. doing about 20 knots+. Engine was very responsive.
After about 4-5mins the engine "suddenly" without warning came back to idle speed. No splutter splutter, nothing just cut back like I had set the throttle to idle.
Checked all the obvious, fuel flow ok, water pump tell-tail good and strong flow and fuel tank ventilation ok!
At idle speed we motored to a beach and had a look at the engine(still at operating temprature), nothing obvious.
Sat down had a smoke and after 10 mins fired engine up and off we went again, went all ok for another 5 mins then the same again, back to idle speed only, with throttle wide open? Let engine cool for 10 mins and once again fired it up and off we went for 5 mins and about 20 knots and then it died back to idle again. To get some knots out of it, so we could get back to the ramp, I held throttle wide open, although it was only giving just above idle revs and we motored back at about 4 knots(long bloody way I tell you). After about 10 mins, without warning with throttle still at max setting, away it roared without warning and then once again, 5 mins later, same old story, idle only.
My question is, is it at all possible this model motor is fitted with a high water temp cut out/safety switch that could be possible faulty ie: shorting out etc? I dont believe from my observations that the water pump is faulty, as the there is a good water flow showing. Im not a guru on outboards of the size so any advice would be greatly appreciated.
Macca