yamaha 115hp alarm

[kevthommo]

G'day,

I have a 115hp yammy on a Southwind SF17 - last full service a year ago and the boat regularly used (at least every 3 weeks). Starts first turn of the key no probs and telltale throwing water. Yesterday went for a fish - few locations and clicked over about 13 km. Return run from final location was about 20 mins and I nudged it up from about 30kph - but not full stick - when an alarm went off. Not sure of revs. Stopped for about 2 mins. restarted no probs and no alarm but speedo no longer working correctly. Mate reckons the alarm was a bell type sound and not a buzzer, as we had previously heard before last major service when we first bought the boat.

Ran it "normally", did a few more clicks and tried a return run at speed, faster than previously. Was pulling 5100 rpm for 5 mins and no alarm. (speedo still erratic). Would appreciate any clues.

Also not entirely happy with previous service place - took 4 or 5 on water tests to sort persistent probs - so any advice on reputable techie in south western syd area also welcome.

tight lines - Kev

[FNQCairns]

Might be the thermostat not fully opening, I am not familiar with yamaha alarms, not enough water pressure to open the popets at intermediate speeds so it can overheat, then at the higher speeds the popets get forced open which saves it from overheat often only just.

Regardless it sounds like a full service is in order

[ozscott]

Mate - they can salt up under the head covers...mine did and caused alarm above 4000rpm...easily fixed with a clean up, but it could be poppit or thermostats sticking...but my bet is salting up in the galleys.

Cheers

[PinHead]

I had a Yamaha 115hp V4 a few years back..the same thing happened but very intermittently..took me back to the low revs bit...sometimes it only lasted 5 minutes and then all was good..other times longer.
After a lot of looking into it by the mechanic it turned out to be the pcb..some corrosion on it causing intermittent problems.

[trueblue]

an alarm can be as simple as running over a plastic bag - pull up, cool the motor and off you go again as long as the bag is gone.

speedo is normally from the pitot tubes, little inlet holes that measure water pressure from the speed you are doing, and pressure is converted to speed.

check those holes

Mick

[bennyboy]

Your speedo inlet tube is in front of the water intakes, if your speedo was playing up and your engine was getting hot it would point to somthing there.

Did you trim the motor up and check the leg when the alarm sounded?