Suzuki DF20AES - prop size

[seadogdave]

Hi Guys (& Gals?),

Been a reader of the forum for some years and got some good ideas from it. I've had 2 hard boats - a 19' with a 175 Merc and a 16' with a 75 Mariner, a few SIBS with a 4 Mariner but now own a Racing Dinghy (RS400 for those in the know) and more recently a Ribeye TS 370 with a Suzuki DF20AES on it. This latest edition has led to my joining and wanting to post.
I used to run the Mariner 9.9 on the RIB but it was underpowered for the load we often carried and it struggled to plane. I decided upon the DF20 upgrade as it was the largest motor allowed on the transom, and it was lightest in it's class (or it was until I decided to add the Electric start). Very happy with the rig until recently as we got to the end of the running in period. With just two in the boat it over revs as the second crew slides back in the boat. With just one aboard it is constant. Tried trimming it in one but still the same. This is particularly annoying as I had informed the supplying dealer what boat it was going on with a view to prop selection and he advised I stick with the standard 9 1/4" x 10".
On a US forum for "Tinboats" I have since read lots of comments about the DF20 over revving with the stock prop. Looks to me like I ought to have gone 11" or maybe even 12" - the largest Suzuki make for it. It's a costly experiment, so I'm hoping someone on Ribnet may have had some
experience with this motor or similar size outfit and could advise. The hull is Alunimium and the whole rig is really light until I get in! The manufacturer keeps referring me to the supplying dealer and he is ignoring me despite having told Suzuki that they acknowledge receipt of my query and will get back to me. Eight weeks later - nothing.

Sorry for the long post, hope to get some words of wisdom back.

Thanks

Dave

[willk]

Welcome to RIBnet (at last )

You'll have read this I'm sure?
http://www.rib.net/forum/f36/suzuki-...iew-71464.html

Sounds like you got a really fine pitch "as standard"

[seadogdave]

Wow that was a quick reply. Must admit I hadn't seen that post. It is pretty recent and started after I began my quest to get help from the dealer.
As chance would have it, immediately after posting my message I checked my email the dealer had finally replied. Unbelievable coincidence. He has recommended a 12" on the basis that with 1 on board it is always over revving and offered me a 10% discount on same.. Having read Fenlanders findings however I am wondering if that may be a step too far?

Timing is everything and had I known before Fenlander bought his 10" I'd have swapped mine for his 12 and tried that. Got a feeling that I'm going to end up with an 11" though.

I don't really understand why two new engines can be shipped with different sized props off the shelf. I wish I'd had his.

Thanks for the link.

Decisions decisions! I'll wait a while and see what if anything others say and let you all know the outcome.

Thank

Dave

[willk]

Hi Dave

Yeah - we aim to please

Your situation is not entirely the same as Fenlander's - he has a soft bottom and that can slow a man down something terrible. What I mean is that if you use the same prop as him, you might get an extra few revs out of it. He'll be along shortly to keep you right!

[Fenlander]

Hi Seadogdave... another David here.. welcome to the forum.

My initial judgement on pitch was largely based on the excellent Russian Youtubes of a DF15 fitted with the different pitch props and revs/speeds recorded (see post #24 of the thread linked below).

Mine isn't run in yet so it wasn't appropriate to do speed trials but I will give my own comparison between 10" and 11" as soon as I can.

However I'm sure you would need at least an 11" if not a 12" with a light load and such an efficient hull profile. There's a guy on here who also has an Aerotec plus a Suzuki DF20 he's owned for about 3yrs. He also briefly had an Frib which has a similarly efficient hull as yours and he suffered over revving on a 10" prop with that or when lightly loaded using the Aerotec.

See his post #21 on this thread where I was asking for opinions on the Suzuki before ordering... http://www.rib.net/forum/f36/suzuki-...ons-71122.html

For our part the V hull of our SIB plus the fact we are usually two sturdy adults + teen + dog + lots of fuel + too much kit means a standard 10" is more likely to be our ideal prop.

Where are you based and where do you launch? How do you like the Ribeye?

Oh and just to be sure when you say... <<< With just two in the boat it over revs as the second crew slides back in the boat. With just one aboard it is constant.>>> do you mean it hits the rev limiter? It's not prop slip/ventilation is it?

[seadogdave]

Hi Fenlander. WillK wasn't joking when he said you'd be along soon was he! Cant fault this response time.

OK so clarity first. I think with the crew sliding forward that little extra weight up front buries the bow a touch and it slows the boat just enough to prevent over revving. If it was ventilating I don't think this would make much difference. I did try trimming it in a bit to be sure but made little difference save for how far back my crew moved before it starts over revving. It is actually uncanny how specific the point is. They reach a certain point on the tube and bang on - first misfire from the over rev protection.

I am erring toward the 12" but there will be occasions when there'll be 4 in it and as much as I don't mind it taking a bit longer to start planing I do want it to be able to achieve it so I'm wondering if 11" is the way to go? Do you still have your original 12"? How would you feel about swapping your 12 for my 10? If it's too high I then only need to buy one more prop - the 11" and I could keep your 12 as an emergency one plus you get a spare of your ideal size. Don't feel obliged. Just a suggestion. Mine is still unmarked. You're a bit far away for a road trip to just experiment.

As for usage, I mentioned that I am a sailor and as much as I sail mostly on inland waters we do like to take the boat to the Seaside occasionally. When we do we try to bring the RIB for safety cover. It has come in handy more than once after the wind abandoned us. Outside of sailing we also use it for exploring the coastline a bit. Find a secluded beach and swim etc etc. Just love being on the water. We used to Scuba dive in our younger years but I now keep a marine reef aquarium instead. In hindsight I'm not sure which was less effort :-)

[Fenlander]

>>>we also use it for exploring the coastline a bit. Find a secluded beach and swim etc etc. Just love being on the water.


Yep that's our use too.

Pretty well every other Suzuki DF20 I've heard of has come with a 10" so it was odd that my dealer told me I had to wait until the outboard arrived before knowing which pitch it would have... but I did notice this in some small print when looking at a Suzuki brochure. Like your dealer my guy's understanding of pitch requirement on a SIB/RIB was lacking and I had to push him to agree if I wasn't happy with the supplied prop he'd swap it out FOC. During the order process he found mine was already fitted with a 12" and pressured me to accept an 11" rather than the 10" I'd have ideally preferred. I accepted the situation though as I thought it would add flexibility if I bought a 10" as well because we always carry a spare on holiday.

So the dealer took off the 12" and replaced it with the 11" he'd ordered in. He muttered something about either returning the 12" through Suzuki or selling it at a discount. As he's located on an inland river I don't think he'll have much call for a 12" on a 20hp. So he could just have it left in stock and be willing to deal.

However I doubt he'd sell it cheaper than you could buy a 12" Solas anyway (£76) as the OE Suzuki 12" ones are around £117...

Propeller Shop :: Suzuki :: Suzuki DF15A / DF20A 2012 -Newer :: ALUMINIUM PROPELLER 3 BLADE 9.25 x 12

Do you have a GPS to know the speeds when this over-rev is happening?

[Chris Caton]

give castle marine in Caernarfon a call, they had a pallet of 2nd hand props which they could rebuild, worked out around half the price of a new prop, they done a couple for me now and I've been very pleased with the results, they also do stainless prop repairs with excellent service too, nowt to lose for a phone call

Home Page

[seadogdave]

Fenlander: she's cutting out at about 22.5 kts. Plenty fast enough for this little boat on flat water, but I don't want to rely upon other's mechanical sympathy not to leave it bouncing on the limiter. I'd rather the load do that. Think I'm erring toward an 11" despite the dealer advice of 12. I think he's just guessing like the rest of us but it's at my expense.

Chris: when I first got into this I did call Castle and they quoted £50 to repitch my existing. The DF15 and 20 use a 10 spline hub unlike the older strokers which used 11 spline. As a result old damaged props in this diameter are harder to come by and I tried several repairers. Given that I need a spare it made no sense to re pitch so Best Buy another and keep the 10 as an emergency spare.
Brings up on other question though. If I saved a £few and put a solas 11 on it, can I be sure it will give me the same step change as an 11" oem prop would?. Though both 11", one may have more or less cup than the other for example and it may muddy the waters if I don't stick with genuine Suzuki to make the comparison. Just adds another variable.

What I really need is someone closer willing to do a swap/ trial.

Cheers for the replies.

Dave

[Chris Caton]

sounds like the waters are already well and truly muddy, good luck with the search, guess you need to find someone with some spare props knocking around

[Fenlander]

>>>If I saved a £few and put a solas 11 on it, can I be sure it will give me the same step change as an 11" oem prop would?. Though both 11", one may have more or less cup than the other for example and it may muddy the waters if I don't stick with genuine Suzuki to make the comparison.


It's a valid thought. A few years back I wanted a same pitch spare for a Mariner 15 2-stroke and bought a Solas. When delivered it was obvious the blade profile was very different to the OE one but I expected it to be fine... until I got it on the water when the 3.6m SIB didn't plane so easily and was very prone to ventilation and over-revving due to slip.

The prop specialist after a little hassle swapped it for a new OE one which was perfect.

In the image below of two props you can see that the Mariner OE one on the left has a far more raked blade design particularly at the leading root. Also the webs the exhaust has to flow past were far finer on the OE one. The Solas is the right of the two and quite different.

The image of the single prop is of my Suzuki 11" which already has that upright leading root so perhaps the differences between that and the Solas would be less than my Mariner to Solas comparison.

But my experience does show changing brands might throw in an added factor.

[chipko]

Hi Dave, welcome to Ribnet.
I think you will know best whether to go for 11" or 12" pitch but we also have a DF20A running on the stock 10" pitch prop.
We run ours on both an Aerotec 380 and Zodiac 3.5 sibs and can easily hit the rev limiter at wot at about 24mph / 21 knots with two up. We usually tow kneeboard/wakeboard so being slightly underpropped solo isn't a problem as we prefer more grunt for hole shot and acceleration.
We briefly had a F-Rib 375 which is probably more similar to your TS370 (even the same weight at 62kg) and running solo with two up hit the limiter at around 26mph / 22 knots. It did feel slightly more underpropped than the sibs, and if we'd kept the boat, I would have tried an 11" prop, which at the same speeds would have reduced revs by around 200rpm.
Although no actual experience, my gut feel is the 12" may be a step too far, as it's an effective reduction of around 400rpm.
Personally I don't mind having the ability to hit the limiter on occasion, and with these motors at least we have the luxury of one!


Nice boats the Ribeye. We looked at the TS400 earlier this year but wanted the ability to upgrade to a 25 or preferably 30hp motor - and even though Ribeye rate the transom for a max 92kg motor, anything over 20hp would void the warranty.
Hope you get prop sorted.

[SlideAway]

Hi,
I'm also new to this site, although I've read and enjoyed much of the advice and content over the last few years.
(After much deliberating) I bought a Suzuki DF20efi last year, and reading this thread, would like to ask a couple of questions:
1/ Is there a difference between the prop slipping and over-revving - I think I may have been incorrectly assuming the former was causing the latter ?!
2/ Do users find the tiller vibrates uncomfortably ? I'd say it's ok but noticeable, whereas on the Suzuki 6 I had before, I don't recall noticing any vibration.
Thanks,
Tim

[chipko]

Hi Tim,
Prop slippage can be caused by either ventilation or more rarely cavitation and the result will be a rapid increase of engine revs coupled with a loss of power;

Propeller Ventilation

Propeller ventilation is caused by air from the surface or exhaust gases being drawn into the rotating propeller blades. This results in the propeller slipping more than usual due to the reduced water load on the blades. The obvious symptoms of this are a sudden increase in engine RPM as well as a possible loss of speed. This commonly occurs when trying to turn the boat at high planing speeds or if the outboard is mounted or trimmed out too high.

In racing conditions this can also occur when following another boat too closely. The small bubbles in the water created by the leading boat can cause ventilation of the propeller of the following boat, with a subsequent loss of speed. This is why you rarely see high speed race boats following directly in the line of the leading boats, even if they are far enough back to be out of the spray and wake.

Propeller Cavitation

Propeller cavitation is less obvious than ventilation, but can be far more damaging. When the propeller blade passes through the water at an increasing speed, the pressure that holds the water to the sides of the blades is lowered. If the water is sufficiently warm, and depending on the speed of the boat, formation of water vapour (boiling) can occur. These bubbles that are produced then immediately collapse, releasing energy that can cause a cavitation burn on the propeller blades. This is one of the great advantages of stainless steel propellers. Due to their superior strength they can withstand cavitation damage better than aluminium and can also be produced with thinner blades to reduce the occurrence of cavitation.

Funny you should mention vibration. The one criticism I have of my DF20 is slightly excessive vibration at low to medium revs. Not felt it excessively uncomfortable through the tiller though.

[Fenlander]

Chipko's explained it well. You should be able to tell if you are suffering ventilation slip as it feels like dipping the clutch on a car while still holding the throttle down then the rev limiter cutting in. If it is because you really need a higher pitch prop and it's just you are maxing out then it will be more progressive until the point the rev limiter cuts in.

If you run with one or two folks and you have a 10" pitch then the opinion is forming that you will likely be able to get to the rev limiter.

I noticed the vibration straight away as this is my first 4-stroke outboard and I'm used to the frantic buzzy revving of 2-srokes. On my DF20 the idle is slow (correctly so), smooth and very quiet and I'd not expected that offbeat vibration that starts just off idle and seems to continue to medium revs when it smoothes out.

It is mentioned in quite a few reviews and by other owners on the net so quite normal. If you look at the tiller twistgrip there is a bit at the end where the diameter reduces and seems to extend it for no purpose as there is no grip on it. There is a damping weight in there to try and minimise how the vibration feels.

I note the DF25 which is a 3cyl doesn't need or have this "weight".

[jeffstevens763@g]

Originally Posted by Fenlander

Chipko's explained it well. You should be able to tell if you are suffering ventilation slip as it feels like dipping the clutch on a car while still holding the throttle down then the rev limiter cutting in. If it is because you really need a higher pitch prop and it's just you are maxing out then it will be more progressive until the point the rev limiter cuts in.

If you run with one or two folks and you have a 10" pitch then the opinion is forming that you will likely be able to get to the rev limiter.

I noticed the vibration straight away as this is my first 4-stroke outboard and I'm used to the frantic buzzy revving of 2-srokes. On my DF20 the idle is slow (correctly so), smooth and very quiet and I'd not expected that offbeat vibration that starts just off idle and seems to continue to medium revs when it smoothes out.

It is mentioned in quite a few reviews and by other owners on the net so quite normal. If you look at the tiller twistgrip there is a bit at the end where the diameter reduces and seems to extend it for no purpose as there is no grip on it. There is a damping weight in there to try and minimise how the vibration feels.

I note the DF25 which is a 3cyl doesn't need or have this "weight".

df 25 true same dia reducing no weight has an offset crank too for smoother running.

[willk]

I've renamed and moved this thread so future readers can find it.

[seadogdave]

Consensus seems to point toward an OEM 11" then. That's what I'll do and I'll let you know what happens. As Chipco Says at least we have limiters on these engines so should it over rev on the occasional one up trip it wont destroy itself. Don't forget though that the ECU on these engines records the number of times the limiter is deployed as well as % of time at various throttle openings. The dealer may frown come service time

Chipko, you're correct my boat has a 20HP limit but the newer TS370 has a redesigned transom allowing it to take a 30. Ribeye documentation is conflicting regarding this but I called them for clarification some months ago. As I need my engine to be portable, the 20 with the electric start is heavy enough and to be fair, fast enough for what I want it for. Listen to me all grown up.

Vibration - yes at lower rpm it's there but not that bad. My Honda Fireblade motorcycle used to give me vibration white finger on the throttle hand. This is nowhere near as severe and is unnoticeable at higher revs.

Can I digress a little. My engine has about 18 hrs on it and is 13 monthis old. The dealer who gave me poor advise at point of sale has quoted me £69 +Vat for an 11" prop and has offered to fit it "Free of charge" if I take it there for it's annual service. he's quoted me £186 +Vat and in a bid to justify it explained it includes plugs and new impeller. Neither of these are listed on the service schedule. OK it lists a valve clearance check (which I doubt he would actually do) but it seems a lot of money for engine oil and filer and lower leg oil change.

Normally I would service it myself but until I gain confidence in it I think a dealer stamp is a necessary evil. This "Main Stealer" price seems a bit excessive though. Anyone got any service bills to compare?

Cheers guys

Dave

[jeffstevens763@g]

Just had my 25 done £65 + vat first service oil filter oil & gear oil
And acording to the manual it's 20hrs or 1 month which ever sooner
Cheers

[Fenlander]

Service costs seem to be all over the place.On this thread post #26 Jeff had been quoted as much as £257 but an alternative place was £65+vat. My local dealer said "about £100" for a yearly but of course it'll be a while before I test him on that.

Edit: oops Jeff beat me to it.

http://www.rib.net/forum/f36/suzuki-...iew-71464.html

Daft to replace the spark plugs at 18hrs when they are just an inspect at 100hrs. Similarly why would he change the impeller at 1yr/18hrs when it's a 3yr/300hrs item!

If I'm reading it right I think the valve clearances are checked at 20hrs then every other year. That check is quite "invasive" by modern standards... if old hat to those of us brought up on older vehicles... so I hope the dealers take care doing this.

Yes the variety of data they can collect from the ECU is staggering and like you I'd prefer not to see it logged I'd been bouncing off the rev limiter time and time again.

The dealer stamp is needed for warranty and I think the killer service cost will be the 4yr with a timing belt change. If my outboard has been reliable up to 3yrs and 11mths I think I'll do that service and the belt myself foregoing the last warranty year.