Noisy pair of DF 140a

[Andrew Myers]

Hi to all
I have just replace a set of 15 year old 2000 hours Honda 130hp with brand new 2015 suzuki 140. On paper all good nearly 130kg less on transom good on fuel 23 knots on one engine. Problem is the noise the rig now makes they are on an 8.5 meter reble plate aluminium boat still manufactured today in Brisbane Qld.
At 5500 revs you can hear the radio stereo talk etc OK and it is making around 101 db on smooth water at nearly all trim ranges. At 3700-4300 you can do none of the above but only pulls 97db on the noise meter. Engine noise is down but the boat seems full of noise it may be something else a resonance with the two engines a sort of droning but it is close to an ear muff job. I wouldn't like to be making important decisions with that going on in my head it's close to debilitating until you get well past those revs. The boat only has 7 hours on its with these engines and isn't likely to get much more until we get so where with this. The last and only time we went out of the harbour since the change the weather was crap but I have been off the water since the wet started in November so got talked into it. It was rubbish 1 meter seas 15-18 knot winds so we were pushed back to 13-15 knots and that rpm range that now makes the boat a nightmare lets just say it was a long 109 km round trip half of it in the pre dawn darkness out of Darwin harbour and remember this is a pleasure boat. First thing the dealer is doing is different props currently running genuine suzuki three blades 13 7/8x 19 he has flown some 14 1/4 x 18 up to try. It's nice that he is onto sorting it I think it will be few things ultimatly with a reduction in the production of the noise or frequency that is the issue and then also stratergy to reduce the transmission into the hull the likely way to go. The hondas in hindsight did have an peice of old and weathered grey thing as a seperation plate between engines and transom which appeared that one day had been compressible to a degree so although it is replaced with a poly ethelene plate like most boats now there could be some clue that in the Honda days they needed to reduce transmission thru into the hull. I will work on it but is there any ideas or revelations out the from twin owners on plate aluminium boats that could save me some time and hair.

[Moonlighter]

Hey Andrew.

I'm in Brisbane area. Dave Claussen makes a great boat, those Rebel's are real fishing machines! When he first started out building them, he also sub-contracted to Cliff Joshua at JBS marine and I had a little 4.85m plate cuddy JBS that Dave built. You can see how good his welding skills are.

I think you're doing the right thing by working with your dealer to sort this out. It sounds very much like a resonance issue with the twins, as those DF140a's are like a sewing machine, very smooth and quiet, normally.

I would think about the engine mounting, BLA sell those grey semi-flexible engine pads that you had with the Hondas. It might be worth lifting the engines off and fitting them. The other thing is to check if there are any cables etc that haven't been secured back properly under the gunwales that are vibrating at certain revs.

Also, the props - are you running stainless props? The sizes that you quoted sounded more like alloy? The Zuke SS props are very nice, run one on my DF115 on my Surtees plate boat. Pretty sure it's a 14x20. Would probably be a decent match for your setup too.

Maybe it I is not propped right and the engines are labouring at those mid-range revs??? That would contribute a lot to noise of the kind you have experienced.

What RPM do you get with the current props, full throttle, trimmed out? You should aim to get at least 6000rpm. If you are not close to that then dropping pitch in the props would likely help a lot. (You can't compare prop sizes between Suzuki and Hondas, the Suzuki gearing is totally different, so the same size props on Hondas will be wrong on the Suzuki's.)

Lastly, if you still have trouble sorting this out, my local Suzuki dealer at Cleveland knows Dave really well and fits out many of his boats with Suzukis for him. You could get your dealer to give him a call and have a chat to get his thoughts. Jon Eadie at Bayside Suzuki marine, tell him Grant told you to call! Jon is one of the top couple of Suzuki gurus in the country, even Suzuki HQ ask him how to sort issues out!

Edit: one more thing! I was talking to Jon about props a while ago and just remembered that he had spoken about an issue with a VMR boat he fitted with twins. They had all sorts of problems getting motors synced and with resonance.

They eventually sent the props to be scanned and found that they were both out of balance, and even though they were marked as the same size, they were actually slightly different pitch!!!

The scan showed that the props had almost an inch difference in pitch! So they had both props tuned, re-pitched and balanced and scanned to confirm they were identical and bingo! Problems solved.

Jon now has all props fitted on twins scanned and tuned so they are identical before the boat gets delivered to the owner.

I reckon you could just have the same problem!

Talk to the dealer about getting both props scanned and checked to see if they are identical. (Of course if you are not getting 6000revs out of the existing props, start with the righ size props and get them scanned).

Cheers

[Andrew Myers]

Thanks moonlighter could be a crossed wire there with the builder Warren Cammeron does the rebels at Clontarf I have tried unsuccessfully to get some survey into of him before but yes a good well mannered boat. I have some contacts with guys that john has set up twin 140 s for some at Fraser Island were I fished for 18 months quite a while ago. John was more concerned about toe in but in truth I haven't spoken to him about this problem directly I did call him about the purchase but the tyranny of distance came in to it and he respectfully excused himself, all good. Props on at the moment are genuine suzuki SS not sure about the trial pair yet haven't seen em if they are alloy its a bit of a a moot point as they will absorb some of the vibe issue. I will reply a bit more when I can get on a computer rather that phone with mini buttons for huge fingers thanks for the interst I will update on this.

[Andrew Myers]

Meant to say as well can get to redline pretty easy 6200 not quite full down on stick but close to it getting 67 kmph. One engine only in the water and it revs out to 5500 but that is with full down on stick easy onto the plane and pulling 42kmph.

[Moonlighter]

Ah yes, my mistake. Confused Warren with Dave! Doh! Rebel instead of Riptide boats!

I've also been on a couple of Warrens boats, mate had a 6m model with 200hpdi Yammy, and another had a 6.5, running a Zuke 225. Solid boats and well built too. We fished off Fraser quite a few times and 1770 as well. Always predictable handling.

The more I think about it the more I reckon you should get both props scanned to see how they compare. I reckon there is a better than 50% chance that the problem will be found there!

Cheers!

[noelm007]

just out of interest, does this noise happen if only 1 engine is running? Not trying to change direction or anything, but it would be kind of nice to test everything before pulling things to bits, try both motors singularly and see if only one does it (I doubt it though)

[Andrew Myers]

Thanks Noel there is a bit more data that I collected last week on smooth water will hopefully try the new props tomorrow if I get time.

[noelm007]

Don't over think the trim thing, and what the gauge says compared to how the motor is, a gauge is just that, a gauge, it can (and does) vary from gauge to gauge and boat to boat, for what you are trying to do here, forget you even have trim gauges.

[Andrew Myers]

Don't over think the trim thing, and what the gauge says compared to how the motor is, a gauge is just that, a gauge, it can (and does) vary from gauge to gauge and boat to boat, for what you are trying to do here, forget you even have trim gauges.

The trim gauges on the old Hondas didn't even work. I am pretty impressed with the new pair of gmi20 multis on the dash. In respects to the out of trim sync it will just be a adjustment to get them both reading the same at the same point on the analogue meter. What's your take on the noise levels on the tables Noel excessive or reasonable.

[Andrew Myers]

OK I tried the alternate props, data collected in red on revised spread sheet attached herewith. Want to run the numbers again to verify the noise readings improvements but it seemed noticeable to the ear as well for both myself and my co tester.
Props were genuine and stainless steel so all good there.
I have a concern with the negative fuel ramifications at the 4000rpm mark and might even check both props again a bit more extensively before I make the final choice. It seems a bit odd to jump up that much at just the one rpm range, the test periods were settled but quick before any lean burn effect could be noticed coming down. The noise one would be realistic as it was quite a lot choppier than the original runs so that would add to the overall noise level assumedly.
On the plus side it revs a bit higher on one engine is so doing planes easier and faster one up. Same loads for both tests but very light.
Next item is to get an EVA foam separator on the transom instead of the hard polyethylene ones and test again, then the final thing I have on the books at the moment is to get whichever the two winning props are to be computer measured and tuned.

[Moonlighter]

Sounds like a sensible plan of attack. Keep us posted.

I will be particularly interested in the results of the prop scanning. Make sue they give you the before measurements as well as the "after" measurements!

[Andrew Myers]

Got some more I for to add but it's getting a bit windy here in Darwin soon so there is a few pressing preperations to make.

[Andrew Myers]

Got some more info to add but it's getting a bit windy here in Darwin soon so there is a few pressing preperations to make.

[Moonlighter]

Keep safe Andrew. That cyclone looks a bit nasty.

[Andrew Myers]

Cyclone Nathan a fizzer again. Am just waiting for the EVA pads and will update noise levels when that is working.