High RPM surge driving me nuts!!!

[summer lake lover]

Hi everybody,

I have a newly acquired 19’ Sunbird fish and ski that’s got a 1998 130HP Evinrude V4 two stroker on the back which I believe has low hours. I deleted the VRO (it was over-oling and reason for previous owners putting it up), new low pressure electric fuel pump, fuel hoses, choke solenoid, spark plugs and wires, removed check valve at fuel tank, opened the screen holes on the fuel pickup, and lots of other things to the boat that shouldn’t have any bearing on the issue at had before I ever got it on the water (it was a hot mess LOL). I have ironed out a lot of the bugs, but I still have an intermittent ¾-WOT surge. It’s about 1hz and pretty low amplitude, it feels about like your moving between 7/8 and full throttle once a second or so. Sometimes it will run 30-45 minutes (or less) like a dream and it starts doing it on it’s own, sometimes it starts doing it during a turn, after you slow down or stop and re-plane again, and sometimes, although very rarely, it does it as soon as you come out of the no wake zone coming up to full speed. When it starts doing it, it will never stop on it’s own (although I never let it do it for more than 10 seconds for fear of leaning/burning a cylinder up). If you come below ¾ throttle or stop for a little bit, it’s about 50/50 as to if it will immediately do it again at full throttle.

The fuel primer bulb is always firm whenever my wife checked it while it is acting up, and I believe my wife squeezed it hard enough one time to flood/choke it down. One of the things I have replaced is the electric fuel choke solenoid, I see it has a shraeder valve on it, could I check fuel pressure there with a fuel pressure gauge? A few interesting observations that I’ve made; loosening fuel cap had no effect, hitting the electric choke while it’s acting up has no effect (like I would expect it to) it does bog slightly when you choke it when it’s running right though. The skeg was bent bad enough to where the flow-steer adjustment (I’m guessing that’s what it’s called) on the end of the cavitation plate was adjusted all the way trying to counter the skegs rudder effect and it still wasn’t countering it fully (I have since straightened the skeg but haven’t had a chance to re-test yet). And the transducer is about 2” deep and throwing a rooster tail and is only about 12” from the outside of the prop’s circle (I’m going to move it before next test), I wouldn’t think cavitation could cause an intermittent prop slip/surge like I’m experiencing, although it seems odd that it will start to surge with turning sometimes. And I understand it's supposed to have Champion QL78YC's in it (I've got a set for next test and tune now), I was sold NGK BZ7HS-10's, do you think this difference in plugs could cause a low frequency rhythmic surge? I believe they're both suppressor plugs, but I've also heard how the older Evinrudes were finicky with plugs, it doesn't feel like it's missing, rather surging though.

I am planning on taking it out for a test and tune in the next weekend or two (weather permitting) and I am trying to figure out what tests to perform. I would like to monitor fuel pressure, battery voltage, IF I can dig up a timing light maybe check the cylinders firing while it's acting up. Is there anything else I should/could be looking at? Someone at the boat ramp made a comment to me about testing the ignition stator, they said surging was a symptom of an ignition stator failing, is that right?? And if so, can anyone point me in the direction of that test? Any and all help would be much appreciated, thanks much in advance!!

 

[tphoyt]

You have a lot going on here but I wouldn’t rule out the prop slipping. Just for kicks mark your prop and hub and if your marks aren’t lined up after your next trip then you will know.
Best

 

[flyingscott]

Get rid of the electric fuel pump. If you have the Vro put it back on and just delete the oil side. If not buy the pump off of an 88 hp and put that on. What happens if you pump the primer ball?

 

[Chris1956]

Over oiling by the OMS pump is usually caused by an air leak on the gasoline side. I would check your fuel line for air leaks. Check the main strainer and make sure the seals and oring are good.

Those motors were not designed for an electric fuel pump. You may be force-feeding the carbs or enrichment circuit.

How is the electric fuel pump wired in? You want the fuel pump to shut off if the motor stalls. That usually requires a relay connected to the starting solenoid primary and to the charging system, or something similar. A direct connection to the ignition accessory wire is a dangerous way to have it wired.

 

[summer lake lover]

Hey that’s a good idea tphoyt, thanks much!! Flying Scott, my wife pumped the bulb while I was driving, she said it was pretty firm, I told her to press it harder just for kicks, and it bogged down, I suppose it unseated the needle valves, it’s a low pressure pump for carbs ( 9PSI, .5 GPM) I actually had the voltage knocked back 25% at first to lower the pressure some, I’m at straight battery voltage now, no effect in operation, do you still think that’s a bad idea? Chris 1956, when you say “main strainer” are you talking about the strainer at the bottom of the pickup in the tank? I opened up the holes some in it, I didn’t look really good where the plastic tube met the aluminum fitting, but I will, the check valve has been removed and all of the fuel hoses are new with clamps now, I don’t know if an air leak was the problem with the VRO or not, I’ve always trusted mixing my own fuel better. The fuel pump I’m using is a Facet 40223, it’s a low pressure pump ( 9PSI, .5 GPM), I actually had the voltage knocked back 25% at first to lower the fuel pressure a bit, I’m at straight battery voltage now, with no effect, that’s a good point with the relay set-up, that will be on my list for sure, right now, it’s just me driving, I expect it’ll be years before the kids take it out, hopefully I’ll still be there LOL, but I will absolutely look into that, good point!! Do you guys think there’s a problem with the pump I’m using? Can I put a fuel pressure gauge on that shrader valve on the primer solenoid? And can intermittent surging be a symptom of the ignition stator failing (like the guy at the ramp told me). Thanks much everyone for all of your help/ideas thus far!!!

 

[racerone]

Some will argue.----The VRO pump is a simple device , reliable too as just a fuel pump.-----No need for electric.----I would test run with a separate 25 liter ( 5 gallon tank ) in this case.----VRO pump is easy to take apart.----Check the pulse limiter ( flow fuse ) too.-----The VRO pump is driven by crankcase PRESSURE pulses.-----There may be an issue with crankcase compression to drive that pump.-----Simple trouble shooting finds answers on outboards.

 

[summer lake lover]

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[summer lake lover]

Yeah, it’s a long story about the VRO pump, long story short it was off of it when I got it, so I’ve kind of got what I’ve got, I couldn’t really see buying one just for fuel pumping, so I went this route, I’ll get a little 5 gal tank with maybe a smaller lower pressure fuel pump for the next test day? Does that sound OK?? I just don’t know what else to do other than use an electric pump at this point, or shell out the cash for a whole VRO just for the fuel pump part of it? I don’t know what the pulse limiter is, but it sounds like it’s used with the VRO?? Can I hook a fuel pressure gauge up to that shrader valve to verify fuel pressure?

 

[tphoyt]

There is no fuel pressure to be found there.
That valve is for injecting cleaners, fogging oil and such.

 

[racerone]

Stop -----Guessing / making assumptions , that will just cost you big $$$$-------Next time at the lake get the missus to drive.------Then take a STRONG flashlight and shine in each carburetor bore.----Observe fuel coming up the main nozzles at full throttle.----I used that procedure in 1975 to diagnose a 105 HP Chrysler while working part time at a marina.-----Main mechanic there had no idea how to do simple trouble shooting.----One of the carburetors had no fuel flow !!

 

[summer lake lover]

Thanks tphoyt!! I’m not guessing/making assumptions, rather trying to figure out what tests to perform next, thanks for the flashlight idea, that’s a pretty good one, I haven’t been able to run it without the cover yet due to the rooster tail that’s flying up from the misplaced transducer. I’ll let y’all know what I find out, thanks for all of the help!!!

 

[summer lake lover]

Well, a little update after testing this weekend, it’s not cavitation, skeg straightened and transducer removed, still has intermittent high RPM surge and now it will intermittently fall on its face on plane out of nowhere, good fuel and all. I know it’s an ignition problem now, I observed spark dropping from multiple cylinders randomly with a timing light while it was acting up. I checked some resistances on the water with the engine off while it was hot and acting up and everything always seemed to check OK, fired it up and it would be fine for a bit again. I unhooked the kill wire and the temperature probes to no avail. I suspect the stator, though I’m not clear on the stator resistance, one place I found says about 450 Ohms, another says about 1,000, (I have a 99 Evinrude 130 V4 2 stroke btw), I saw it as low as 400 Ohms but as high as 450 Ohms with open to ground, I was a little leary of checking voltage output of it with the engine running, it’s kind of tight back there on the water at that, does anyone have any ideas on my stator resistances? Thanks much in advance!!!

 

[racerone]

S.L.O.W.----system kicking in ?

 

[summer lake lover]

I verified it wasn’t overheating then unhooked the tan temperature sensor wires along with the kill wire, that should keep it from going into slow mode, right?

 

[oldboat1]

As previously suggested, replace the electric pump with a standard pulse pump, probably from an earlier model of similar hp. The VRO pump by itself works fine with premix and the oiler disconnected, but it sounds like there may have been problems with the VRO pump. Get clear about which pump, and how to hook it up (lots of prior posts).

 

[summer lake lover]

Installing a new pulse pump wouldn’t have any bearing on dropping spark though right? I witnessed it Saturday, intermittently dropping spark on cylinder 2 and 3 with a timing light.

 

[racerone]

I predict that motor will be running like new next week end with a new stator.

 

[oldboat1]

hope so. learned a new use for a timing light anyway.

always considered electric fuel pumps extremely dangerous on outboards. Maybe technology changed.

 

[summer lake lover]

It was Racerone that gave me the idea of using a timing light, (pretty smart I thought!!!) although I think on a different forum. I was thinking the internal resistance of the stator is low on the scale at 400-450 Ohms, one spec I found says 450-700 and another says about 1,000 Ohms, so that’s where I was leaning. Racerone, would you replace the timer base while you were in there, it’s another 300.00, but I’d be right there at it, are they as prone to going out?? Thanks in advance!!!

 

[racerone]

In my opinion there are lots of electronic parts replaced on a hunch.-----Often folks then say " motor still runs the same "-------Go ahead if you can solve it with money , you do not have any problems.