Remap/chiptune df80?

[Murray]

In my owners manual (DF70A, DF80A, DF90A) 2009 specifications for DF80A 5000-6000 r/min. Im guessing if you tried to get above 6000RPM your rev. limiter would kick in.

FA9DC9F9-0B26-46A4-8D1E-8CE2C4F90F33.png
The above screenshot is from my service manual

[FlyingDman]

Yeah the rpm rang seems to be 5000-6000. At the moment my engine will get to 5200-5300.. It does sound logical to pick another prop and seen if RPM going up actually makes that difference. I'll try to test in summer.

[Moonlighter]

Thanks for your input Moonlighter. I'm actually looking at installing another prop. Currently my engine has a 3x13.75x17 am I right in assuming that I should start using a 3x13.75x15 to achieve the higher RPM?

I am not familiar with your boat, and there are many variables involved, so I’m not prepared to suggest the correct prop.

In most countries, Suzuki has a local website that includes boat tests (locally available boats) of each hp engine that includes details of the prop used. So have a look there. You may find your boat or something similar that will give you a starting point.

Also, there is a sticky thread in this forum that deals with setting engine heights and selecting propellors. Would be well worth you having a read of that thread to gain a better understanding of the issues involved.

You have never mentioned engine height in this discussion, and it can be a MAJOR factor affecting engine performance. The sticky covers that too.

link: https://www.suzukioutboardforum.com/...the-right-prop

[FlyingDman]

This is great information, thanks! Much work to do and checks to perform.
Might you be interested; the boat in this matter is a "Steelfish Rescue 700". A Dutch built and designed aluminum sloep-style boat with high speed capabilities. The outboard engine is placed inside the boat at the back, in some sort of an engine-room. The boat weighs approx. 2500pounds.

I will start looking at engine height when the boat is back in the water, this spring. And I will need to find just that Suzuki dealer here that can advice and allows some testing. Thanks all!

[FlyingDman]

Oh and also thanks to Murray for all your input and off course you also shared that sub to closing the right prop.

[Murray]

This is great information, thanks! Much work to do and checks to perform.
Might you be interested; the boat in this matter is a "Steelfish Rescue 700". A Dutch built and designed aluminum sloep-style boat with high speed capabilities. The outboard engine is placed inside the boat at the back, in some sort of an engine-room. The boat weighs approx. 2500pounds.

I will start looking at engine height when the boat is back in the water, this spring. And I will need to find just that Suzuki dealer here that can advice and allows some testing. Thanks all!

I searched the internet looking for a picture of where the outboard would sit, couldn’t find anything. If the outboard doesn’t sit on the transom I’m wondering if engine height as per the sticky applies? To me the post above (post #19) looks like an inboard. Out of curiosity could you post a picture that shows the engine mounted in the boat?

[FlyingDman]

It's actually an outboard yet it is placed inside the compartment in the back.I will post a picture soon (need to take some photo's when I'm there).

[Moonlighter]

I searched the internet looking for a picture of where the outboard would sit, couldn’t find anything. If the outboard doesn’t sit on the transom I’m wondering if engine height as per the sticky applies? To me the post above (post #19) looks like an inboard. Out of curiosity could you post a picture that shows the engine mounted in the boat?

I also thought the same thing Murray - this is a very different hull/boat design and it obviously means that the engine installation will be very different to a normal transom mounted one. I do recall seeing some pro fishing net boats years ago, with the engines mounted internally as described here. Keeps the prop well clear of nets being dropped and hauled over the transom area.

Although, I do think that mounting the engine too deep will still cause excess drag…. Its just physics, and every centimetre deeper means more drag and that reduces rpm and slows the speed.

And, the rule of getting the Suzuki revs up to the top of the recommended range definitely still applies.

On that point, the max recommended rev range is not the same as the revs at which the rev limiter kicks in. Like many Suzukis, my 2010 DF115 rev range is 5000-6000 rpm, and it is propped so it can hit about 6150, and my dealer was very pleased with that. The rev limiter kicks in at about 63-6400rpm.

This is one of those cases where the knowledge and expertise of the specific boat’s manufacturer comes into play, along with the knowledge of dealers who sell those boats and install engines on them for customers. Thats where I would start.

Our flying Dutchman also may be lucky and find a local owners group for those boats and be able to get some suggestions from them. One important thing to remember when doing that is that due to the Suzuki engines gear ratio being very different, and thus typically running larger dia and pitch than the other brands, you cant run the same dia and pitch prop on a Suzuki as you can on a Yamaha, Merc etc.

Cheers!

[FlyingDman]

I have been to the boat today and took some pictures of how the engine is mounted.
Some background own the boat: I'd a Steelfish Rescue 700 (7 meter length). The boat manufacturer sits in the Netherlands and used to sell used rescue boats in e.g. Amsterdam for the canals there. At some point he switched business and designed his own boat, made out of aluminum and mounted with an outboard engine that is built into a engine compartment in the back of the boat. The Reschue700 was sols with engines from 70 to 90 hp. The fun of the boat is that is is suitable for low speed cruising (can fit up to 10 persons in it) but is also capable of higher speeds up to approx 45km/h.

[FlyingDman]

Part 2, pics wouldn't go into one post.

[Murray]

Thanks for posting the pictures. I’ve never seen that particular set up. Learn something new every day.

[Moonlighter]

Very different setup for sure!

That said, to me, the motor does look to be set very deep below the hull. Its very hard to judge what might be the optimum height though on that hull.

I dont know how easy it would be to do, but can you lift it say two holes higher? Then re-test and see what happens to rpm at WOT.

As per the sticky thread, the general idea is to get it as high as possible without the prop losing “grip” on the water. If there’s still good grip 2 holes higher, then keep going up until you cant go any higher or until the prop doesnt hang on, then drop one hole down. Its a trial and error game.

And that prop looks fairly chunky! Been bumping lots of hard stuff! That complicates things because its definitely going to be a part of the problem.

Ideally, you would start with a prop in good condition, then get the engine height optimised, see where that leaves you re engine revs, and then look for a more suitable prop to get you up close to 6000rpm.

[FlyingDman]

So, plenty of leads for me to go on. Thanks!
The prop does have some " experience". It hit some rocks a while ago. This is also one of the reasons to wanting to swap it. I'll have to look into raising the engine up. I imagine it's not going to be that easy.

Looking at the 4th picture (first series) the anti-ventilation plate is near flush with the hull. I'm not sure if the engine can be raised since it is mounted in the engine-compartment which is closed from the top.

Any thoughts on a potential new prop? I'm leaning towards testing a smaller pitch prop. But I could consider 4-blades, different diameters etc. Any hints could help making up my mind.

[FlyingDman]

To follow through: today the boat went back into the water. I have replied the prop and went from pitch 17 to 15. Also, the engine received service (oil, impeller/water pumps etc), spark plugs etc were replaced. The engine now revs up all the way to 6000 rpm and the top speed of the boat went up as well as the acceleration. So, to conclude: mission accomplished!