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Old 01 April 2016, 19:21   #41
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Weight... hmm not sure as it's 8-10kg more which is about the difference between a Tohatsu 9.8 and my Mercury 15 and they felt the same... light on the tiller.

Perhaps it's the blooming great anti-ventilation plate holding all that splash down!

I'll observe (or feel) more carefully next time out.
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Old 02 April 2016, 13:52   #42
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Just back after a week on hols (no internet) and this forum is more anally-Aerotec than ever! My anti splash plate for the BAT-Mariner/Mercury splashing ended up falling off so I'll be making a simpler one this year. No amount of height adjustment cured it for me, some sort of plate or deflector is essential.
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Old 02 April 2016, 14:30   #43
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I had a yam 15hp on my aerotec and the splashing was really bad, put a 25hp yam on it and the splashing was pretty much gone.
Plus it was a lot more fun with the 25hp ...
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Old 09 April 2016, 12:51   #44
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I am still trying to work out why I had zero splash on my Aerotec 380 at full or any speed and then on the next trip, had lots of splash at full speed only. I did change the prop but it was identical. I wonder, if the floor was done up a little differently on the straps on the non splash trip. I am going to monitor this closely. 25HP
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Old 09 April 2016, 13:10   #45
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I think any small change can alter the splash... as you say perhaps floor pressure and also how your kit & tank weight is spread about.
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Old 10 April 2016, 08:57   #46
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Hi Fenlander, there cannot be a more forensic discussion on splash than this! Having thought about your comment about tanks, YES this was a change. When I had two 22L tanks end to end and two up, I had no splash. When I had the 22L tanks side by side under the seat and two up, I had splash at full speed (only). I think this might have changed the shape and weight of the floor, so will put end to end again this time and report back.






I can't wait to get my outboard back from Chas Newens!
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Old 10 April 2016, 11:09   #47
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Shame Locozodiac has gone off the radar - he was the master of SIB/engine height set-up and splashy OB techy do-dah...
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Old 27 June 2016, 11:19   #48
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Aerotec transom splash issue.

Started this response on another thread but thought more relevant here.
Always suffered the dreaded 'splash' to a degree although never into the boat so more of an annoyance than the real problem many suffer. To try and bottom this out I knocked up a couple of temporary transom raisers at 50mm and 65mm.
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Only tested solo this weekend so findings not fully conclusive yet, though I fear the underlying cause is not just engine height. Splash is worse on a lightly loaded boat and on mine only at near max speed.
Have been running 25mm riser as stock, now tried 50 and 65mm. No top speed gain (21knots) with any, splash is getting less with more height but not yet fully eliminated. Not suffering any significant ventilation even at 65mm so may be room to go higher though reluctant to do this. Also trimming either side of optimum makes little difference to splash, but significant to performance.

In my opinion it's the disturbed water exiting off the concave transom/v-floor edge curling up and inward hitting the lower leg. The AV plate sits nicely at the surface of the main water flow with 50mm raiser, but the intermittent secondary flow hits the leg randomly and above the splash plate. This is what causes the splashing. Photo below indicates this soft corner between the transom and floor. Note: 25mm riser in pic.
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Below are a couple of crude sketches to try and indicate water flow off the Aerotec and a typical SIB.
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Have tried a splash plate in the past, which helps, but would rather eliminate splash at source rather than mask the problem. However, now I know the splashing is not significantly affecting performance, then a combination of raising the engine to optimum and then a splash plate to deflect the pesky secondary intermittent water flow, may be the way to go.
The quest continues.
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Old 27 June 2016, 11:24   #49
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That is a very well argued diagram - I'd always thought it was somehow the deep V specifically at the transom (unique to Aerotec) that caused it but maybe the edge curve as you say?

My anti splash guard stops it coming in 100% - just directs it out back. Sadly no added water jet type velocity is gained....

[EDIT[ Just been out to look at mine sitting on it's side and you have to be right - the shape is almost perfectly designed to direct water off that curve as it meets the V and straight up in the air.
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Old 27 June 2016, 11:41   #50
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Aerotec transom splash issue.

Thanks Max. Would love to know the thinking Bombard had behind the concave transom. Surely if it had a straight V to match the floor it would give a nice 90 deg. hard edge to the joint. Hope it's not just to save material when cutting transoms from a standard sheet!
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