4-stroke EFI run in rev limiter?

[JacquesR_ZA]

Hello fellow Suzi's,

So I'm new around here.
Grown up behind an 85hp Suzuki waterskiing.

So recently bought a DF15A - 15hp fourstroke EFi powering a small foldable 3.2m duck.
It's the ideal solution for our summer vacation time next to the Grootbrak river in Western Cape province.
There are many simalar rigs, also with 2-stroke Suzi's and the Chinese knock offs.

After some months waiting for motor delivery, finally got it and past weekend first time in the water.

Took the manual seriously with regards to run-in procedures, where I,
- first just idled for 15mins
- then 1h 45 min in gear idling

on the water I've then kept it
- for the next 1hr not over 4000rpm

but then from there the manual advises one can increase throttle, get it to plane and ease off power.

Even with almost 4hrs on the timer, it's refusing to go over 4000rpm.

It takes forever to plane - nothing over 4000rpm.
It's out of character for rigs like these.

On the plane best I could see was like 4500rpm.

My understanding is that this one should rev up to 6000rpm.

Dealer recons it's running in protection on the motor and it will get better?

Is this true?
Anything else likely a problem?

Regards,
Jacques

[JacquesR_ZA]

WhatsApp Image 2021-09-25 at 11.47.51.jpeg

[Moonlighter]

There is NOTHING in the engine control system that prevents a new engine being revved to max during running in - it is purely up to the operator to control the throttle to keep it within the rev ranges recommended during the running in time.

So if that is what the “dealer” is telling you, they are talking rubbish.

There is one sensor (the neutral throttle switch) that prevents the engine being over revved in neutral, but that limits rpm to 3000rpm approx. So, if that switch is stuck or not adjusted correctly engine rpm will be limited to 3000rpm and acceleration from idle to that speed will be doughy and when it hits 3000rpm, it will run like a race car engine that is hitting the pit lane limiter - it will miss and buck and run bad.

You said you eventually got the boat to plane and the engine maxxed out at 4500rpm, correct?

Was the engine running smoothly at that speed - eg no indication that it was misfiring or otherwise running badly?

And how do you know the rpm? Do you have an accurate tacho fitted?

If there are no indications of the engine running badly, then the most likely things are that

- the engine is sitting far too deep into the water, so you can raise it up?

- the wrong propellor is fitted. Can you check the prop size and report back - bear in mind that Suzuki engine run a very different gearing ratio and that they will therefore run very different prop sizes to other brands. The standard prop I believe is 3 x 9.25 x 9.

- the engine is somehow not getting full throttle. Im not familiar with the DF15 but can you take the cowl off (engine not running) and check that when the throttle is fully opened that the linkages etc indicate that they’re actually fully opening?

[JacquesR_ZA]

Moonlighter many thanks - that's really valuable input!

I have this "Runleader" tacho from Amazon which is supposedly accurate.

Correct, on takeoff with "full" throttle on the tiller it would stay around 4000rpm.
Eventually on the plane best I could see was like 4500rpm.

Smooth running, no misfiring.
With 2 hours on the water, it just died on me at idling speed in gear - this happened twice, but then started again on first pull.

Can't really raise it a lot, unless I adapt the transom or would it help to trim on the manual trim adjuster?

I haven't checked the prop size, but it's the standard one from the box.

Also thought I could check the tiller throttle cable tension back at the throttle body.

Mostly appreciate your help!!
Jacques

[Boberstop]

Well I'm new here also. I have a DF15ATHL that is doing just about the same thing. I have about 4 hrs. on it. Starts fine and idles good, but surges at 1/4 throttle. I got it to just under1/2 throttle yesterday, then it started again.

[JacquesR_ZA]

Well I'm new here also. I have a DF15ATHL that is doing just about the same thing. I have about 4 hrs. on it. Starts fine and idles good, but surges at 1/4 throttle. I got it to just under1/2 throttle yesterday, then it started again.

Welcome!

So far my dealer has helped with a diagnostic - everything checks out well on the laptop with no errors reported.

In the manual I had a read about the trim setting - a manual pin setting on DF15A, cause on my duck the transom is not perfectly vertical, but at some steep angle.

Also measured the recommended mounting height, measured from the bottom of the boat and it's a perfect fit compared to the manual recommendation.

Yesterday tested again on the water at different trim settings - little improvement, could get at best to 4900rpm with throttle pushed at max. Plains out in 6sec's.
Hour meter now on 6hrs done.

It's already better, but my dealer suggest we could also look at a different pitch prop - it came supplied with a 10-pitch.


Regards,
Jacques

[Boberstop]

I think mine is a 9 pitch. I bought it from OnlineOutboards..I sent my dealer a note to see about getting it looked at,but it's getting late here in the North.

[Boberstop]

Hi Jaques: I noticed that my motor came adjusted so it's trimmed all the way in towards the boat. I'm going to move it out one notch and see if that helps. Weather's getting colder and wetter here in Michigan, so might not get too much more use till Spring. I'll let you know if it helps, plus I have power trim, and will try messing with it.

[JacquesR_ZA]

I'll let you know if it helps, plus I have power trim, and will try messing with it.

Thanks - will be very interesting to know.

[Boberstop]

Thanks - will be very interesting to know.

Well, Jacques, I moved my motor out one hole.on the pinned adjustment. We fished yesterday and it seemed a little better. I'm in the second part of the break in. I'm running it just below 1/2 throttle. It ran good for a stretch, but was missing a little towards the end.. It is better , I think it just needs that break in time.

[Moonlighter]

Well, Jacques, I moved my motor out one hole.on the pinned adjustment. We fished yesterday and it seemed a little better. I'm in the second part of the break in. I'm running it just below 1/2 throttle. It ran good for a stretch, but was missing a little towards the end.. It is better , I think it just needs that break in time.

Didn’t you say that your engine has power trim?? The pin doesnt do much in such cases, it just sets the down limit for trim setting.

If your engine has power trim, then perhaps you aren’t familiar with how to use it. This info may help if that’s the case. If you already know this, apologies in advance for telling you how to suck eggs!

Start off with the engine trimmed down. Accelerate onto the plane, and as the boat starts planing, gradually trim out, you will feel the engine revs rise and the boat accelerate faster. The bow will lift steadily too and the boat will run at a better level.

Once its planing properly, steadily open up to full throttle, and trim out slowly step by step until the prop loses grip and then quickly trim down a little so it grips again. If the boat porpoises at this trim setting, trim down a touch more until its steady. That is the optimum running angle.

If the engine hits the rev limiter and starts missing at higher revs before WOT and full speed, its likely that you should run a prop with greater pitch. If you have a tacho you will see the rev light come on, or if the light is on the tiller arm it will come on and you should hear an alarm.

Jacques -

if your engine doesnt have power trim, then the pin sets the trim angle of the engine. If you havent already, put it out to the next hole and test again. The compromise you have to make is - how much bow lift when accelerating onto the plane is acceptable, and at the same rime, achieve a good running angle at speed. The more trim out you can get at planing speed, the faster the boat will go and the more the engine will rev. And its more economical too.

So, the idea is to test one hole further out, then if that is OK, put it one more hole out and test again. Repeat until you find the optimum setting that give the best compromise. Of course, you need to do the test with your “normal” load of people and gear, placed where they would normally be located in the boat. Small boats are very sensitive to load placement fore and aft.

[Boberstop]

Thanks Moonlighter. I don't think my motor has enough hours on iit yet to get it up on plane. I haven't had it above 1/2 throttle. Maybe I should? Whenever I start going close to 1/2 it runs rough, so I back off. I never had a problem with my 90 Suzuki with the break in. Dealer told me to take it easy for few hours, don't run wide open, vary your speed. Maybe I'm taking it too easy on this one. I have a 9 pitch prop. What would I go to if I changed it? Thanks

[Moonlighter]

Something isnt right if it starts running rough at half throttle. Although, some more detail on exactly what you mean by “running rough” would help.

Re the running in, its a bad idea to have the engine under load with the boat pushing lots of water and not on the plane. Give it some throttle to pop it onto the plane , and then ease it iff so its still planing comfortably with the engine not working hard to keep it planing.

The ecu only records rpm in 1000rpm bands so you can, for example, run at anywhere between 3000 - 4000rpm and it will simply record that as x hours in that rev range. You can therefore be running at 3950 rpm and it records that the same as 3050 rpm.

[Boberstop]

It feels like it's missing and it surges. I'm going to get it up on plane next time out and see what it does. I have no RPM meter, so will just try to get 3/4 throttle. Thanks for your help.

[JacquesR_ZA]

Jacques -

if your engine doesnt have power trim, then the pin sets the trim angle of the engine. If you havent already, put it out to the next hole and test again. The compromise you have to make is - how much bow lift when accelerating onto the plane is acceptable, and at the same rime, achieve a good running angle at speed. The more trim out you can get at planing speed, the faster the boat will go and the more the engine will rev. And its more economical too.

So, the idea is to test one hole further out, then if that is OK, put it one more hole out and test again. Repeat until you find the optimum setting that give the best compromise. Of course, you need to do the test with your “normal” load of people and gear, placed where they would normally be located in the boat. Small boats are very sensitive to load placement fore and aft.

Moonlighter thanks - I've tried different positions with the trim pin and best one is second slot from the transom.
Then it takes like 6 seconds to reach a plane - that's with myself, wife and 2 kids on board.

We are not particularly heavy people but I know during summer at the river we will probably have another passenger or so.

Had a chat yesterday with a coastal dealer - his advice is also for me to look at a 9 pitch prop rather than the 10 pitch I got with the motor.


Thanks,
Jacques