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Old 27 June 2012, 09:02   #1
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OK probably a stupid question but I think worth asking just in case..

I was using my new go pro yesterday and filming from different positions on the boat. One position was filming the engine during a blast. During playback today I noticed that the engine during throttling up moved forwards - not a huge amount but definitely moved forwards, then during throttling down to a stop it moved back again. Its not the transom - thats solid - just the engine.

I will try to upload the video to youtube and post a link back in a min so you can see what I'm talking about. Cheers





OK think thats the link. Thanks
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Old 27 June 2012, 11:19   #2
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I don't see the engine moving relative to the transom; I suspect you're seeing the entire transom moving forward (a bit of tube deformation) under power. I'd say its pretty normal.

jky

Edit: Or is it a RIB?
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Old 27 June 2012, 12:03   #3
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I wasn't sure it was the transom moving as its well braced etc being a searider. the video does not do it justice in std def. its more noticeable at the end when the motor stalls ( out of petrol). You can see it move forward then.

If you say thats normal then great news as I was not sure and thought it better to ask and look silly on here than out at sea when the motor drops off ;-)

Come to think of it now you mention tube deformation, the tubes were not up to full pressure. Would that make a difference?

Thanks
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Old 27 June 2012, 12:50   #4
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All looks pretty normal to me!

Don't forget the outboard is held in place by rubber shock absorber mounts, that might account for a little movement, but what I think you're looking at is the leg loading up under thrust and then relaxing when wave hopping or throttling down, this will have the effect of having a tilting action on the outboard.
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Old 27 June 2012, 12:52   #5
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Quote:
Originally Posted by Hightower
All looks pretty normal to me!

Don't forget the outboard is held in place by rubber shock absorber mounts, that might account for a little movement, but what I think you're looking at is the leg loading up under thrust and then relaxing when wave hopping or throttling down, this will have the effect of having a tilting action on the outboard.
Nice one put my mind at ease now. I blame the go pro! Would never had seen it moving if it wasn't for that :-)

Thanks guys
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Old 27 June 2012, 12:57   #6
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I would agree with Hightower ,possibly just a bit of flywheel and prop torque too acting on the rubber engine mounts when powering up . i had a Johnson that seemed to do that from new,
some do occasionally wear out .
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Old 27 June 2012, 13:00   #7
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Before watching video I thought it would be mounts on a merc 3 pot. Very common. Looking at the video I see the Yam do very unlikely mounts.

I suspect it's the power trim, either low fluid or leaky ram. Try giving it a good yank on the cab plate, trying to tilt it up, see how much movement you have and where from
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Old 27 June 2012, 15:24   #8
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Quote:
Originally Posted by Boats&Outboards
Before watching video I thought it would be mounts on a merc 3 pot. Very common. Looking at the video I see the Yam do very unlikely mounts.

I suspect it's the power trim, either low fluid or leaky ram. Try giving it a good yank on the cab plate, trying to tilt it up, see how much movement you have and where from
I checked the trim fluid level before this trip and it was low. I topped it up before going out.

I will see if I can move the motor as you say by grabbing the cav plate etc. Do you think this amount of movement is not normal then?

Cheers
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Old 27 June 2012, 16:34   #9
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Originally Posted by CornishAvon View Post
Come to think of it now you mention tube deformation, the tubes were not up to full pressure. Would that make a difference?
Yup.

Though even at the correct pressure, you can expect a bit of flex when the motor comes up on power.

jky
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Old 27 June 2012, 16:39   #10
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It's important that tubes are at optimum pressure, especially if they are in contact with the water under way. Low pressure can cause a rippling effect that damages seams and strakes. Don't ask me how I know
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