Df115 hitting rev limiter at 3000rpms

[Suzukijosh]

Hello all I am new to the forum. I've recently bought a 2003 Carolina skiff sea chaser from a friend at work for a good price and am now trying to figure out the hopefully last little bug that it has. (I'm a newb to boating but can fix/diagnose most engine problems)
Ok my problem is, when I have it on muffs I cannot get it to rev above 3000 rpms. I have no codes or alarms on the tach. I've checked the neutral switch on the engine since everywhere in the net points towards it as the problem. It shows via a ohm meter to be closed loop when in neutral and when in forward or reverse it's open loop. There are no problems in acceleration up to that point and no bogging it just seems to hit the rev limiter.(3000rpms).
I have a manual on order but it hasn't came in yet So that's why I'm here.
This may be a dumb question but is the motor designed to rev past 3000rpms on muffs? I am going to put the boat in my name tomorrow so I can finally put it in the water to see if it will rev past 3000 in water.
Anyway thanks in advance for helping

[Moonlighter]

The engine has a rev limiter that prevents it revving beyond about 3000rpm when it is in neutral.

I presume you have it in neutral when it is on the muffs. That being the case it is doing exactly what it is supposed to do.

[Suzukijosh]

I don't think there is a way to rev mine in neutral, when I did it it was in gear. Thanks for the response

[Moonlighter]

Josh, you have said you are new to boating, so from someone who has owned and run boats for more than 30 years, here is some good advice. I also own a Suzuki DF 115 myself so i can speak with certainty about that model.

it is extremely dangerous to rev any outboard engine beyond idle speed in gear when it is out of water and running on the earmuffs. You should not do it! Apart from the danger to any people nearby of a prop spinning at under power at big revs, there is no load on the engine and you risk causing engine damage if you rev hard and then back off. It is simply not a sensible, or necessary, thing to do.

And yes, there is in fact a simple way to rev that engine when it is out of gear - there is a lever on the top of the throttle control box that is the neutral throttle lever, lift it up and the engine will rev. But it will hit the limiter at approx 3000rpm. The prop may spin when you are doing this, but if you chock it with a piece of wood, it will not spin.

If however you are actually revving the engine hard, in gear, while running on the muffs, and the engine starts missing and farting at 3000rpm, then most likely it is hitting the rev limiter. I have never done this myself for reasons as per the first paragraph above. Bloody dangerous!

I would suggest that you put the boat in the water, and complete the testing there. Far safer.

If it will not rev past 3000rpm in the water due to the rev limiter cutting in and the engine therefore "breaking down" and missing etc but running smoothly to that point, then yes, you might well have a problem with the neutral throttle switch on the engine. Its pretty rare that this switch causes problems, but it is possible. It is not an expensive or difficult part to replace.

It might also be advisable to take someone who has some boating experience with you on that first trip on the water. Things like power trim need to be used properly for the boat to run safely and perform to expectations. It might all look simple but some guidance from an experienced hand is the smart thng to do. After all, if things go pear-shaped out there on the water, you can't just step out and walk away!

One more thing: how long has the fuel in the boat tank been sitting there? Stale fuel, especially anything with ethanol in it, is an enemy that can cause engines to play up badly and in fact can cause quite extensive engine damage. So fresh fuel is advisable.

Take care and be safe around that prop!

[Suzukijosh]

Thanks for all the advice moonlighter. I was slowly giving it throttle easily until it started to cut out. As far as not going over idle in gear I never new that but now I do!!
I drained all the gas that I could before I put new fuel in it along with seachem(I think that's what it's called and some fuel stabilizer.

My throttle/control box (sorry for my lack of boating terminology) doesn't have the lever like my father-n-laws champion bass rig. It only hat the throttle and tilt/trim button.

I will give you an update tomorrow if it will in fact rev past 3000 or not and we can go from there. Thanks again for coaching me through all of this!

[RussArran]

Hi Josh, if you have a newish Suzuki throttle binnacle, there's a black rubber circle on the side; push the centre of this to disengage the gear shift (try it with the motor off first - the throttle lever will probably feel looser.)

Good luck with the boat!

[Suzukijosh]

Thanks RussArran I will try it soon as I get my kids off to school

[Suzukijosh]

Hello again I just wanted to give a quick update. I will finally get to put the boat in the water Tuesday. I did find the rubber to push in on to rev the engine in neutral! Thanks.
I am wanting to install a new fuel/water separator and was wondering which brand you guys would recommend? It looks like a bunch of people use racor (forgive me if the spelling is wrong) with the water drain on the bottom I'm thinking about this one unless y'all point me towards a different type.
Anyways sorry no good news since I cannot put it on the water due to the parks and wildlife offices being closed but I will post back with a update soon as I can get it out on the water. Thanks again

[Moonlighter]

Racor are very good filters. The clear bowl lets you see if any water is in the fuel too.

I would recommend them. Change filter element once a year is a good idea.

[keakar]

Racor are very good filters. The clear bowl lets you see if any water is in the fuel too.

I would recommend them. Change filter element once a year is a good idea.

I agree, and since you are new to boating its a simple thing to remember that once a year you do EVERYTHING maint wise.

change the water pump impeller
replace the lower unit gear oil,
replace the engine oil and filter (4 strokes)
spray anything that's rusty anywhere with wd40 or rust preventative spray
loosen and retighten the lug nuts adding never seize to the threads
remove your wheel hubs and inspect and regrease your bearings replacing them if you see any signs of wear pattern on the bearings or races
check all rollers and bunks on the trailer
check your safety gear condition like fire extinguisher and life jackets
inspect everything else like trailer wiring, tie down straps, anchor lines, & mooring ropes

there are regular maint charts based on usage but if you look at the timing on the chart, if you do everything at the same time each year you don't overlook anything.

since you just got the boat I suggest you treat it like it needs everything now and check it all so you know when you last checked everything and that everything is in good working order. trusting your friend to tell you he checked everything already is a recipe for problems so inspect everything yourself and don't even ask him when he did this or that last.

also when trailering long distance it is a good idea to stop half way and get out to feel the wheel hubs and tires, they should be warm but not hot. hot means something is wrong. on short trips its ok to wait and feel the hubs and tires when you get to the launch. when it comes to tires and wheel bearings the temperature is what tells you something is wrong.

[Suzukijosh]

Well good news and bad, good news is that everything besides the engine works properly. Bad news is that the thing does cut out at 3,000 rpms. So I am now back to diagnosing that.
Thanks for all the info y'all are giving me and check list I have already replaced most of the things you mentioned keaker and what I haven't changed yet is on order and will be replaced soon as it gets in.

Ok so I've changed plugs. Engine and lower unit oils, put brand new batteries,steering cable.
I have a racor filter with water catching bowl/drain on the way along with new bilge pump since I accidentally broke the discharge of the one on it now. Drained fuel and put new fuel in the tank with a injector cleaner and sta-bil.
If it was y'all's boat what would you check next? Through researching I've decided to check the vst filter/screen whichever is in there by the high pressure pump. I may also go ahead and change the neutral switch on the engine since everyone says that's the one that'll limit it to 3000 rpms cause the engine thinks it's still in neutral. I have checked it with a multi meter and it shows open loop when in gear and closed loop when it's in neutral. Any other ideas what to check? Thanks in advance

[keakar]

your tests show the neutral switch is working correctly so you don't need to replace it.

I am suspecting the wiring harness has a short in the wires for the neutral switch so the wires are connected making the motor think the neutral switch is closed.

I am convinced its an electrical problem either with the wires or what the wires plug into and you eliminated the neutral switch as a cause so follow the wires to the other end and see where they go. unfortunately I think that goes through the ECM

do you have an electrical diagram for your motor? if so take some time to trace out the circuit and see where it goes

[Suzukijosh]

I was tracing the wires and I didn't see any of the two for the neutral switch (colors) going into the ECM unless they change to different colors somewhere within all of the tape. So I started pulling the tape off and it started raining again so I will resume soon as the rain stops and I can pull the cover back off the engine.
Oh and I don't have a electrical diagram yet

[keakar]

I was tracing the wires and I didn't see any of the two for the neutral switch (colors) going into the ECM unless they change to different colors somewhere within all of the tape. So I started pulling the tape off and it started raining again so I will resume soon as the rain stops and I can pull the cover back off the engine.
Oh and I don't have a electrical diagram yet

I wouldn't go unwrapping the wires, just trace it from what you can see and use a wiring diagram for what you cant see.

on mine the wiring diagram shows the wires come from the ecm so it goes through it on my motor and im guessing it does on yours as well.

you can download a service manual for your motor online for like $10 so you should definitely get one

[Suzukijosh]

I have a wire tracer my dad gave me years ago and followed the wires the wire that sends 4.45 volts to the sensor comes from behind the ECM in what seems to be a brown terminal block and the return wire yellow with a green stripe goes to one of the two relays that's behind the ECM. There was another identical relay so I swapped them and the problem is still there so it isn't the relays haha.
The only thing that I found funny was the neutral switch on the engine had 4.45 volts going to it and the return wire which goes to the relay only had .49 volts coming out. I may be wrong but I thought this neutral switch just broke the signal. I may be wrong but shouldn't I be getting the same out of the neutral switch that was going into it? Oh and I have a manual on its way. Thanks again