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Old 09 May 2016, 03:03   #71
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>>>bow twitches side to side not a problem but never noticed that before on any sib might be weight related?

If you mean the boat sort of steering itself at the bow I'd say you have a little too much weight up forward.
do you think so might have 50 kg tops and its only at WOT i thought it might be me sat on one side [port] and the prop rotation trying to push on my point of axis like being on your heal on an ice skate.
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Old 09 May 2016, 03:31   #72
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Suzuki DF20AES - prop size

Jeff,
Good turn of speed you're getting. Gut feeling I wouldn't go below 10" prop personally, even though you are well below 6000rpm max.
If loaded ok and bow steering you could try trimming out a notch to lift bows, which may also give you a bit more speed. More likely prop torq as you say twisting port side down. I also get this marginally at terminal velocity and I sit starboard which helps counteract.
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Old 09 May 2016, 04:54   #73
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I'm with Fenlander on the pitch selection. You can divide rpm by the gearbox reduction, multiply that by pitch inches and divide that into a mile of inches but it won't really tell you anything. Each prop make is different and as soon as you take slip into account, which you will always get when screwing into a fluid, be that air or water all the sums go out the window. Slip varies with drag / load too and it must change a little dependant on whether you're in salt or fresh water too as their densities differ. The pitch is given purely as a theoretical distance the prop would advance in one full turn on paper. That's it.

I can't say I ever noticed any bow steer on my sibs, even the ones with the inflatable keel and air deck floor. They all just slid around corners. The ts370 though is like its on rails if you get the bow trimmed down just the right amount. It'll turn on a sixpence and try to eject anything higher than the tubes. It just grips like crazy and I need to be super careful carrying speed into turns.

Dave
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Old 09 May 2016, 05:27   #74
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Quote:
Originally Posted by chipko View Post
Jeff,
Good turn of speed you're getting. Gut feeling I wouldn't go below 10" prop personally, even though you are well below 6000rpm max.
If loaded ok and bow steering you could try trimming out a notch to lift bows, which may also give you a bit more speed. More likely prop torq as you say twisting port side down. I also get this marginally at terminal velocity and I sit starboard which helps counteract.
should have tried sitting on the other side just i dont handle well with the left-hand but it would have given an indication. re; trim i am on second hole out so will give third a try. as it is i wont buy another prop until i get this bow steer sorted.
thanks for input cheers
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Old 09 May 2016, 19:25   #75
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As mentioned in the DF20A impressions thread I had the first day out with our 10" pitch prop we've substituted for the 11" the outboard came with.

Given that we carry a hefty load and the Aerotec needs a little more power to move its deep V through the water the 10" prop has transformed the feel of the outfit. Odd that such a small change on paper can have such a great real life effect.

By the time the engine was run in enough to try some speed runs the sea state had fallen off so I could only snatch some brief results before there were grumbles from the crew and there was no chance to swap back to the 11" for its results.

I didn't take any figures for the 11" pitch last time out either but I could feel it was too high geared.

The 10" repeatedly climbed to 5750rpm and 19Kts and on one brief occasion I saw 20.5Kts without the rev limiter cutting in but it was far too rough to take my eye off the sea and look at the revs... I'd guess around 6000-6100rpm.

Given our load today was about the norm I reckon this (usually standard supplied) 10" pitch prop is perfect for us. The DF20 with this prop has given the boat the ability to jump on the plane in a moment and power up to 19Kts in quite short sections of sea between the rough bits. For me that's more important than outright speed which could just be possible with the 11" pitch, smoother water and dumping some weight (crew!).
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Old 10 May 2016, 03:01   #76
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reading both reports david i see some similarities getting the bow up as chipko mentioned and going down a pitch, you are getting an average of say 20 knots in those conditions so you could quite easily get to 22 knots on the flat.i think that my extra 5 hp is taken up by the boat weight and extra kit [console/flare box frame]so based on that the 11" is an inch too far i think i will play some more before buying but thanks for the info.

cheers
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Old 12 May 2016, 07:59   #77
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So after asking my supplying dealer for a breakdown of the service cost into parts and labour and asking why he was doing things from the 2nd and third year service in the first year he stopped responding. Read into that what you will.

Next dealer along was cheaper 90 plus parts but he also said he was going to change the plugs and the impellar. I questioned why he would change the impellar after 18 hours use and he said I could skip it if I wanted but he would still open it up and look at it anyway so may as well change it. I'd rather leave it undisturbed until it needed attention. Jury is out on that.

The third dealer took all the details and promissed me a call back. So far he has failed to do so, but then he failed to call me with a price on an engine when I was buying it in the first place too so I went elsewhere.

If I were Suzuki I would be monitoring the performance of their "approved dealerships". They seem pretty poor to me in my area at least.

Dave
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Old 12 May 2016, 08:14   #78
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So with my Honda warranty the service(s) can be carried out by "any competent marine engineer"... I'm not sure what construes a competent engineer... I've rebuilt a few Mini engines in my time but I bet they'd not see me as a competent engineer if push came to shove... still... With Suzuki can you do same, just get a local independent to do it?

I have no issue with my local Honda approved service centre but good to know I have options...
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Old 12 May 2016, 09:14   #79
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Had quite a few issues with posts not happening and having to re post. Anyone else see that? Got to the point where I copy all post text before submitting in case it happens again.
SDD - that can happen if you take a while to compose a post - generally when you have not selected the "remember me" box when logging in. Basically you time out and your post is toast
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Old 12 May 2016, 09:14   #80
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>>> he was going to change the plugs and the impellar. I questioned why he would change the impellar after 18 hours use and he said I could skip it if I wanted but he would still open it up and look at it anyway so may as well change it.

They drive you mad... why do they do it? The impellor is an inspect at 1yr and replace at 3yrs item... no uncertainty... that's the schedule.


>>>ith Suzuki can you do same, just get a local independent to do it?


No they state Suzuki dealer only... and without the Suzuki software a non dealer can't really see what's been going on. So unless you are willing to "self insure" from day one then it's down to finding the best value dealer.
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