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Old 30 August 2015, 12:35   #1
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Yamaha F30 overheated :-(

Feck sake, finally got out on a calm day and engine overheated on the way home , wasn't on full throttle either, only 4000 revs when she started smoking out the top exhaust, couldn't Rev it over 1800, turned it off when the pee stream started to become spluttery,

Flushed it out since getting back and it started on the muffs first turn, pee stream strong as always

What do you think happened? Water pump? Or thermostat ?

Help :-(
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Old 30 August 2015, 12:47   #2
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Impeller key
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Old 30 August 2015, 12:58   #3
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Kelp or bag blocking the intake?

jky
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Old 30 August 2015, 14:47   #4
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I took the intake guards off and found nothing, there was a little bit of debris in the pee hole exit, but the pressure is good , if the thermostat doesn't open would that cause the overheating?
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Old 30 August 2015, 15:02   #5
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If the thermostat doesn't open yes it would overheat. I'd want the stat out and checked.
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Old 30 August 2015, 15:07   #6
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Ok, when it was getting serviced and a new timing belt the mechanic said he checked the thermostat !
Worse case how will I know if there's damage done?
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Old 30 August 2015, 15:16   #7
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Davie is a man of few words built on many years experience. I'd follow his pointer first.

As for long term damage compression testing and possibly a boroscope would help, but personally I'd want an expert to look at it.
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Old 30 August 2015, 15:39   #8
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Sorry just though - you tested on Muffs. I've never used muffs. Would there be water flow even if the impeller failed? If so then water flow means nothing.

Testing in a bucket would confirm that as if the paddles on the impeller are missing or the key has failed and the paddles are just spinning freely. BUT testing in a bucket with failure would result in potentially more damage...

Your mechanic who checked the thermostat presumably also checked the impeller?
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Old 30 August 2015, 16:01   #9
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I'll take off the lower unit tomorrow and see what the story is...

No confidence in the mechanic or the guy running the dealership

Looks like it's not my year , off the water for awhile :-(
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Old 30 August 2015, 16:43   #10
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Sorry just though - you tested on Muffs. I've never used muffs. Would there be water flow even if the impeller failed? If so then water flow means nothing.

Testing in a bucket would confirm that as if the paddles on the impeller are missing or the key has failed and the paddles are just spinning freely. BUT testing in a bucket with failure would result in potentially more damage...

Your mechanic who checked the thermostat presumably also checked the impeller?
My Mercury doesn't put water out of the tell-tale with just a hosepipe connected to the muffs unless the engine's running. Turn the engine off & the telltale stops.
Check the stat.
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Old 30 August 2015, 17:04   #11
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My Mercury doesn't put water out of the tell-tale with just a hosepipe connected to the muffs unless the engine's running. Turn the engine off & the telltale stops.
Check the stat.
Yeh - but your impeller would stop the flow as its not turning. But if the impeller is damaged water can flow past, or if the key is damaged it can spin on its spindle.
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Old 30 August 2015, 17:54   #12
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The impeller would act as a plug.
If the key is damaged/missing the pump drive shaft will be turned by the engine but not pump water as the impeller isn't turning & blocking the water supply so I doubt if you'd get any water from the telltale.
If there was no impeller in place or a number of its blades are badly damaged or broken then I expect it could be possible for water to reach the top of the engine on muffs when not running.

Be interesting to see what would happen with the OPs if run in a bucket. Or what he finds when he drops the gearbox to check the impeller & key.
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Old 31 August 2015, 02:58   #13
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If the key is missing /broke ... Why would putting water in the intake at pressure (I.e muffs) not just spin the impeller on the shaft and allow water past?
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Old 31 August 2015, 03:13   #14
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Dont know why but I have had 3x F30/40 keys shear this year I have never seen a key snap for years. They seem to wedge in at idle but lose drive anything over 1500 rpm.
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Old 31 August 2015, 03:17   #15
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Going on my own engine & its impeller I'd be very surprised if domestic water pressure could turn the impeller. The blades are very curved when in position.
Plus the muff cups are flexible to allow them to conform as well as possible to the water intake & consequently don't form a waterproof seal in the way that a screw in adapter would, water can escape round the edges. I use the muffs for flushing only as per the instructions in the manual. If I want to run for extended periods or at higher revs then I use a cut-in-half plastic 55 gallon drum.
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Old 31 August 2015, 03:18   #16
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Dont know why but I have had 3x F30/40 keys shear this year I have never seen a key snap for years. They seem to wedge in at idle but lose drive anything over 1500 rpm.
Bad batch?
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Old 31 August 2015, 05:26   #17
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Bad batch?
All on pre fuel injection
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Old 31 August 2015, 06:55   #18
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The impeller is larger than the pump housing that's why you have to rotate in the direction of the shaft so the vanes lean back hence the resistance caused will prevent tap pressure spinning the impeller unless it's completely shot then the bits of rubber go up the waterways had it happen to one at work resulting in overheating if the engine has stood a while with an old impeller it could have work hardened and broke up best to strip the leg off have a look. Look on you-tube for D-Rays shop impeller service.
Cheers.
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Old 31 August 2015, 15:32   #19
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Mechanic said he checked the thermostat and it was fine, don't know wtf he checked but it certainly wasn't fine!
Don't have a kicker engine yet but because the engine was freshly serviced by my local Yamaha dealer and had a new timing belt, I felt I'd be safe enough to take the kids for a quick spin, after it overheated it took me over an hour rowing to get back, fairly pissed off now... :-(
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Old 31 August 2015, 16:39   #20
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Send him the picture asking what he actually checked
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