Suzuki DF50 What speed do you get??

[Nautek]

I have a Suzuki DF50 on my 26X

At 5000rpm no Ballast, 2 persons on board I get 10.5 knots (12.8MPH)

I have a 12 X 9 C 3 blades prop

At 7000 rpm I get 12.7 knots

What do others get with this motor speed wise and what prop do you have??

I have searched the site and looked at all the suggestions but I would like to know what people are actually getting speed wise for the revs and exactly what size prop they are using

Allan

[puggsy]

SEAHORSE also has a DF 50. So far I have not operated without the water ballast. But the most revs I have ever got is 4,200...Its something I'll have to check out...I cannot even imagine 7,000...
. I have had a prop change but stuck with the same type as original. Puggsy

[Frank C]

!

Frank C:

Not criticizing, but you can probably fine-tune your request by searching first. There's a lot of reading in the archives, plus the benefit of many owners not currently aboard. I searched for you on Suzuki DF50 prop, and found 86 hits. I've chosen 5 threads. The first listed thread, by Mark, was his first question about props, in Oct '05. The second thread, also by Mark, is particularly good w/very comprehensive testing (May '06). This latter thread has very extensive notations on speed attained with many different prop tests. I'm unsure what else you were reading, but that thread should give you pretty precise answers. Of course, you'll get answers from current 26M readers too, but Mark's 2nd thread is a gold mine. Correct Prop for Suzuki DF50? Michigan/Piranha/Solas Props on Suzuki DF50, 26M Sukuzi DF50 Prop Prop pitch for DF50 on 26M Michigan Wheel on Suzuki DF50 As for your speed, 14 mph seems a bit slow, but lots of issues contribute to speed variations. We don't know how much gear you carry; What kind of bottom paint, and How your DF50 is mounted.

[Nautek]

Hi Frank

Thanks for the threads

I am still confused as we seem to be coming up with a lot of test figures but from them the only thing I can see is the 12x9 prop I have might be under proped but I am not sure what to go to from there.

The boat is not loaded with too much gear
The motor is mounted with the cavitation plate below the hull as it should be
The hull has new anti fouling on it

Although there are a lot of comparisons they are all over the place with different rev ranges which make it hard for a comparison

I will do further investigation with the prop people here in AU and see if they can come up with something

Thanks for your help

Allan

[Frank C]

Allan,

If you have an ablative antifoul paint, I'd think your top speed seems about right. That paint probably slows a boat by 2 mph. IIRC, reports are very rare of a Suzi-50 getting anything greater than 16.5 mph. When reading the archives, you need to look for those variations, and level your own playing field. When others are reporting their speeds into this thread ... you need to do the same.

As for the 12x9x3 ... your max rpms seem appropriate for that engine. You might find a 4-bladed prop provides a nicer (smoother, vibration-free) ride, and a better mid-range cruise. The earlier threads will give some guidelines for changing to the 4-blade ... just a guess, you'd need something like a 12x8x4.

FWIW, several owners later changed from Suzi-50 to the 70, or a bigger Evinrude. IMO, that's prolly a waste of cash, as I rarely cruise my Suzi-60 above 15 mph. One big difference though, the larger outboard can cruise 15 mph at only 3800 rpms, so it's a bit less frenetic cruising.
Welcome ab'd, Allan, & best of luck.

[Nautek]

Hi Frank

On the first post I did notify my speed and rpm
At 5000rpm no Ballast, 2 persons on board I get 10.5 knots (12.8MPH)
I have a 12 X 9 C 3 blades prop
At 7000 rpm I get 12.7 knots


The manufacturers recommendation for WOT is 5900 to 6500 rpm that is why I think I may be under proped
I may need to go to a 12 x 10

I am awaiting a call back from Piranah and see what they come up with.

Thanks for your help

Allan

[BigNige]

Hi Allan,

I have the DF50 on my 2007 26M.

The dealer offered the engine with the standard 12 pitch 3 blade prop but we immediately found this to be too much and the engine would only lug up to about 5300 rpm (manuf recommendation is 5800 to 6200 at full throttle). I ended up with a 10 inch pitch as it was available locally at the time and complied with BWY's recommendation of either the 10 or 11 inch depending on load. After 9 months experience with this prop I must say that it was for most occasions OK (I single hand and don't carry too much extra weight on board, I also have an ablative antifouling but certainly had found no noticeable effect from adding this whilst using the 10 inch prop perhaps because of its blue colour!!) but I did find that the engine wanted to over rev when I emptied the ballast tank and I could get up to 15.4 knots at 6400+ rpm but the engine began to sound rather rough at these revs.

A couple of weeks ago I got a new 11 inch prop and ran some comparison tests. They were a bit inconclusive but generally indicated a 5 - 10% increase in speed at the same revs up to 4000 revs which I suppose would be expected. Flat out speed with no ballast was identical at 14.8 knots but revs had dropped from 6250 to 5800 and the engine felt and sounded more comfortable. With a full ballast speed had dropped from 12.7 knts at 6100 rpm to 11.8 knts at 5600 revs which surprised me particularly as at 5000 revs speed had been up from 8.8 to 9.5 knots and there may have been some tidal effect that I hadn't allowed for so I'll be trying that again.

My feeling at the moment is that either 10 or 11 is OK for most situations with the Suzuki 50. 9 inch is too small and would probably damage the engine if allowed to run for too long. For me the sea has to be glass smooth to even attempt flat out running but even then I don't like hammering an engine for too long and drop back to 4500 -5000 rpm. If you want speed and comfort then probably a 70HP with a larger diameter prop is the way to go. If I knew as much when I bought the boat as I know now I would probably have gone that route.

Nigel

[Wrudd3]

Allen,

I have a 2005 26M with bottom paint and a new SDF50 on it. The prop was a 11.75" X 12 pitch. I could only get 12.7 Kts at WOT and no ballast. As mentioned by Nigel the DF50 WOT range is 5900 to 6500, anything below that is lugging the engine, anything over is not good for keeping the parts together Max HP is at 6200.
I was told the RPM limiter is set to 7200 that’s when the engine may sound rough.
I digress, so I put a 11.5 X 10 pitch (per BWY) and now I max at 6200 RPMs at WOT, no ballast and bottom paint, 16 gallons of fuel aft and 12 gallons of water under the vee berth weekend food & bedding. The best speed with that set up and just me on board is 14.7 kts.
Your 26X is about 300lbs lighter than a 26M. I think your diameter (12"?) is too much load on the motor. The 11.5 X 10 may give you max legal RPM or go with: S1100 Aluminum 3 blade 11-1/2 11 pitch zuki part number 58100-95222-019.

I have been told by a speed shop the greater the pitch the better speed. The diameter is the force that pushes the water. the 12 " is pushing too much water and the 9 pitch is not screwing you through the water very fast.
more blades only have more push. you need less diameter more pitch, a balancing act.

~Will~

[Nautek]

H Will & Nigel

Yep I agree that I need more pitch.
I didn't think of 11 inch but reducing the dia and increasing the pitch I think is the way to go.
Yes I found at 7000 rpm the motor sounded rough.
I want to run somewhere between 5 an 6000 rpm. The closer to 5 the better however I think I am lacking a bit of performance.

Allan

[DAVEWVU86]

When running my 26m with a df50 WOT I used to run about 18.5mph w/o ballast. Can't remember what size/pitch prop. It was whatever stainless prop Bill at Boats4sail sends you out the door with.

[Wrudd3]

Dave, That is about the right speed for a boat without bottom paint and no alge slime.
I'm presuming you trailored the boat when you had it.
~Will~

[DAVEWVU86]

It was bottom painted and trailer kept most of the time. Occasionally kept it on a lift or in the water but generally not for more than 5 days to a week at a time.

[Dimitri-2000X-Tampa]

I don't agree that a 12 inch prop pushes too much water. My Merc bigfoot 50HP (and HP is HP is constant) turns a 14X10 just fine. I can hit 19mph by myself and close to 17mph with the whole crew of 7 aboard (and that is WITH ablative bottom paint). Seems like you wouldnt want to turn anything with any less pitch than 12X11, and maybe even consider 12X12 if you are lightly loaded most of the time.

[Wrudd3]

The Merc 50 Big foot is pretty much the same as the Yamaha 50 Hi-thrust that I had on my 26x for 10 years.

From the merc WEB page “BigFoot models are perfect for pontoons and large boats, while the Standard models are ideal for aluminum fishing boats, bay boats and inflatables.”

The reason they called them Bigfoot and Hi-thrust was due to the lower unit’s gear ratio was set up to spin a larger diameter prop.

I had a 14 X 11 prop on mine that was cupped so that it would run at 5500 rpm, the max HP. At that time, at WOT, no ballast.

Another reason the merc and Hi-thrust can spin a larger diameter prop is it’s larger displacement (18%) than the zuki, and more torque design.

It’s not just HP, torque is a big factor, especially when the motor is working hard trying to spin the prop all the time . . . no coasting, no down hill.

Mercury 50 Displacement 4 cyl 60.8 Cubic inch or 995 CC,
Suzuki 50 Displacement 3 cyl 49.7 CI or 815 CC,

It does help that the 26x is 300 lbs lighter than the 26M (re to my prop and Allen’s)
I think the rule of thumb is ‘around’ 200 rpm for every 1 inch of pitch. So if Allen Did go with a 12 x 12 it may put him at the peak HP of the DF50, 6200 and speed . . . ??

Allen, Let us know what you end up with!

[Nautek]

I have just heard back from the Piranah agents in AU
They recommend 11.5 X 13 C
They said that would get my WOT to 6200 to 6400 rpm
The manufacturers spec is between 5900 and 6500 rpm
So we might be on the right track
I am staying with the 3 blade as I already have the Piranah prop on now

Allan