Surging at 4000 rpm ?'s again

[Gorilla0178]

If its not one thing its another. Went out for another run today, the motor surges at about 4000 rpm. How can I tell if its the prop slipping or a power issue? I'm not sure it happened the first few times i took it out, but it happens now. I've worked out the fuel issues it had, the boat takes off great and will run great right up to about 4000 rpm if I give it more gas it surges between 4000-4500.I might get it to 5000 but eventually it starts to do it. I tried the prop at all heights and it still does it. If its in neutral it will rev quickly and crisply up to 6000+ no issues. Speed seems to fluctuate with the surging. The motor seems to be getting plenty of fuel, the primer bulb is always hard and the bowls seem full all the time. The speed when it happens is about 60 or so. It also stalls sometimes after letting off and making a turn arould. Not sure if thats part of it. The set up is a 17 action marine, 200 johnson, 5.5 jackplate, propshaft 4" below pad all the way down, level with pad all the way up, stock lower, 13.5 25pitch 4 blade bass boat prop. Any ideas where to start with this? I really want to get this worked out.

[spbutler]

I chased what I thought was fuel problems for a month and it was ignition, the power pack.
You shouldn't rev your engine up in neutral, you could blow the motor because of no load.
I used a inductive timing light to catch the problem, losing spark on 3 cylinders intermittently. In a separate issue I did have a prop that slipped but it was during take off.

[Gorilla0178]

I didnt rev it much, just gave it a good step on the gas. I dont think it is the prop, but i want to be sure. How did you catch it with a timing light?

[Forkin' Crazy]

What's it do when you push in the key?

[Brabender]

Does it get progressively worse as you run it?

[Gorilla0178]

Havent tried pushing in the key while running, didnt think of that. Would that rule out fuel?

It doesnt do it at all running under 4K, if I step on the gas it might get to 5K or so, then it drops to around 4K and if I give it gas from then on it revs between 4-4.5K back and forth. Kind of like hitting the limiter, but i know its alot higher than that. Runs good up to then. I think I do remember it from before, but it had to go awaw for a short time i think, I've run it higher than 4.5K but not much, If I've seen 5.5K I'de be suprised. But then speed and experance has something to do with that.

[Gorilla0178]

Any ideas, I really hate to spend hundreds of dollars to take it to the mechanic if i can figure it out. I'll put it in the water again this week and see what happens when I hit the primer. Not sure what else to check.
I'll check the plugs and wires too.

[Gorilla0178]

I was doing some research online, read someone else had similar prob. when he pushed the choke it took off, I'll test that this week, if that is the issue how do I fix it. Assuming its that simple to find.

[spbutler]

You need someone in the back with an inductive timing light (clamp on) on one of the wires while you drive and see if it goes out when problem happens and if light doesn't go out move it to a spark plug wire on the other side, still doesn't go out try the rest of the wires. At least you would know if your losing spark. Another test would be a spark tester at idle to see if your getting sufficient spark for each cylinder. They're cheap from any auto store.

[racer]

What year 200? with or without air box? what mains in the carbs?

[Gorilla0178]

1999 year, with airbox, not sure what mains, its a stock motor.

[Gorilla0178]

Well I bypassed the water seperator/fuel filter, to make sure its not restricting fuel. There should be no reason for it to be restricted now Its free and clear. I ran it for a bit on the hose and no prob. I dont know what the fuel press is, but I undid the fuel line to carb #1 and it squirts plenty of fuel, I couldnt pinch it off by hand. There's no leaks or anything, and all carbs are getting good fuel. I'll take it out for a run tomorrow, Keep you posted....

[Gorilla0178]

Ok here's what I found today. I bypassed the fuel filter for the test today. It fired up with a little hickup today, so be it. I warmed it up and slowly ran it up to about 50. Give it more gas runs up a little more then starts to surge, push the key in, no change. I stop make sure the primer ball is pumped, then take off hard, boat runs up to 5k still going, then starts surging. I stop again and check the primer ball, takes 3 squeezes to fill the carbs. Do the same thing over, running great for about 30 sec then surges, primer ball thakes 3 squeezes to fill. I did this a bunch of times and it was always the same. Runs great for 30sec or so then surges, if you let off the gas and then try to give it more it gets worse. So I'm guessing the fuel pump isn't keeping up with the demand??????? The good news is I feel like I was driving it the best so far, until the surging starts. Running real straight, and nice. I think the surging screws the handling up, today you could feel that everytime it surged, it would torque the
boat over to the left and screw up the handling. What do you think????

[JohnR]

Assuming the fuel pump is on the motor, I would say something is wrong between the bulb and the tank. The pump is sucking plenty of fuel and emptyying out the bulb because the fuel can't make it to the bulb. Maybe there is a restriction in the tank. I've heard that there is a check valve on the end of the pickup inside the tank and sometimes it gets stuck or somewhat stuck closed.

John

[Gorilla0178]

The fuel pump is on the motor, the tank is brand new, just had it made, it had tape over the holes when I got it. Dont have a antisiphon valve on the tank, then its just 10 or so feet of 3/8 hose, then the bulb to the motor where there is a small inline filter. I dont see where the restriction would be, thats why I bypassed the big filter, to be sure it was a straight path to the motor. Still did it. Would not having a antisiphon valve be it? I wouldnt think so.

[Forkin' Crazy]

No, the anti-siphoning valves sometimes cause a restriction. If you don't have one, you can cross it off your list. ;)

Check the fuel pump.

[Riverratt]

Is the tank properly vented?

[Gorilla0178]

Yep, tank vent is clear, even have a overflow check valve. I had to have the tank made due to the vent situation, It better be vented right.

[racer]

I would install a vaccum gauge with a clear piece of hose to make sure you dont have any air bubbles. If the vaccum is over 5 you need to find the restriction, 3 or less and running out of fuel you need to check the pump.

[Ray Neudecker]

I have run into some of the small aftermarket filters for cars causing a restriction when used on an outboard.

[JohnR]

Would it be acceptable to remove the filter under the cover if one had a spin on filter/separator in line?

John

[Gorilla0178]

The little filter was put on by a OMC mechanic and its new.

[baja200merk]

Just hook up a drill pump in line and make sure you charge the dewalt before you go out :D :D :D

If there was a restriction between motor and tank you can usually feel it when you pump the ball if it doesnt suck the ball flat when running (if its a bad enough restriction). Since you said it runs good when you pump the ball im guessin fuel pump is taking a chit on ya. U know what to do :thumbsup:

[Gorilla0178]

Cool Been looking....

[spbutler]

I'll tell you again, although it was at different RPMs, I went through all this and found it was a power pack problem. I swore it was fuel related. I spent my whole weeks vacation down the Jersey Shore replacing every fuel line I could, primer bulb twice, fuel pickups, fuel vent hoses, both filters twice. Got home replaced the rest of the fuel lines, oil injection lines and even the VRO fuel pump.
I could have went out and bought the timing light down there and at least of known it was ignition. Once I found out it was ignition there was so many different things that could have caused it. I got lucky, I banged on the power pack when it was happening, with a screwdriver handle and could hear the other cylinders kick in.
I'm not saying it's ignition but it may be easy to rule out or confirm with the timing light.
The aftermarket power pack was cheaper than the VRO pump itself, let alone all the money I spent on hoses, fliters, clamps, pickups etc.

[baja200merk]

If it was the power pack, pumping the ball wouldnt fix the problem.

[Forkin' Crazy]

I'll tell you again, although it was at different RPMs, I went through all this and found it was a power pack problem. I swore it was fuel related. I spent my whole weeks vacation down the Jersey Shore replacing every fuel line I could, primer bulb twice, fuel pickups, fuel vent hoses, both filters twice. Got home replaced the rest of the fuel lines, oil injection lines and even the VRO fuel pump.
I could have went out and bought the timing light down there and at least of known it was ignition. Once I found out it was ignition there was so many different things that could have caused it. I got lucky, I banged on the power pack when it was happening, with a screwdriver handle and could hear the other cylinders kick in.
I'm not saying it's ignition but it may be easy to rule out or confirm with the timing light.
The aftermarket power pack was cheaper than the VRO pump itself, let alone all the money I spent on hoses, fliters, clamps, pickups etc.

Well... "I'll tell you again"... Do you have an OMC factory manual? Have you ever worked at an OMC facility... wrenching on boats? It’s pretty easy. Process of elimination. Never used a timing light unless setting the timing. If you want to check the secondary ignition for leaks, pop the cowl and run it at night. Watch for the light show. ;)

If you are going to check the ignition, you have to load it. Rapair makes a nifty device just for this. I have the eight cylinder model. You set the electrodes 7/16” off so you can check the quality of the spark. You may also recognize an inconsistency in spark timing. This can be from a bad wire, coil, primary wire, ground, etc. It does give you a starting point though.

Good luck!!!

[Forkin' Crazy]

Just hook up a drill pump in line and make sure you charge the dewalt before you go out :D :D :D

LMAO!!! On second thought... Will the seals handle E85? :eek: OOPS! :D

I love my Mallory pumps!!! :cool:

[Gorilla0178]

Im going to have to take it out sunday with somebody to pump the bulb for me, I'll bring a timing light also. I has a mech check the thing over when I got it, he said the ignition system was good. Not that it couldnt be bad now.

[spbutler]

My point was just that it could be ignition, the "I'll tell you again" wasn't how I meant it to sound.
It was that I wasted alot of time, money and vacation thinking it was fuel and a timing light is just one easy way to see if you lost spark completly on 1 or more cylinders, which can be caused by a variety of things. I like that night idea, I had a Dodge Ram Charger that you could see sparks flashing.

[Gorilla0178]

I'll check both when I take it out. It could be anything at this point. I'm hoping its a easy fix.

[perfmarine1]

I am going with spbutler on this one. #1 running prob on OMC is packs. Fuel pump and lines is easy to diog just pump bulb while running!

[Gorilla0178]

Well I should be taking it out with my pops today and he'll pump it while I drive. If it runs for more than 1 min at 5K+ then thats prob it. I I had it checked recently and the mech said all that checked out. I know one could be bad anyways, I hope to be able to repeat the prob today and then pumping it fixes the prob. I'll come home and order a pump if it turns out to be it.....

[perfmarine1]

Also that motor has a fuel vacume switch alarm,if it had restriction it would be beeping!

[Gorilla0178]

I dont have the stock gauge or horn sounder, and I had to remove that switch because the vent hole on it was leaking fuel. I went out today and had my dad pump it while I drove it as fast as I could, it constantly stayed over 5Krpm without surging. I verified the issue it was having before the test and it still was doiln it.So I guess the pump isnt keeping up. I'll be getting a fuel pump I guess......

[gfinch]

Seems like an easy enough test that answers the question. They probably still sell a combo vacuum/pressure guage at any parts house.
I would install a vacuum gauge with a clear piece of hose to make sure you don't have any air bubbles. If the vacuum is over 5 you need to find the restriction, 3 or less and running out of fuel you need to check the pump.

Whats up Al!

[Gorilla0178]

I hope, been chasing this problem since i finished the boat, hope this is it. Then I can actually learn to drive it.

[racer]

Gary just working to many hours and you?

The fuel test I mentioned is easy and eliminates the boat, it takes me less than 5 minutes but I already have the tester. While the engine has a vaccum switch that turns on a buzzer (if hooked up and working) they dont go off at 5 inches of vaccum yet 5 inches is boarder line especially if the pump is weak. Through the years I have seen to many fuel problems missed when they are easy to check.

Check the system before buying a new pump.

[Gorilla0178]

Other than the vacuum test (which I dont have a gauge) what else is there? My fuel system consists of the new tank, 10 ft or so of hose, primer bulb, a small filter to the motor, I bypassed the fuel/water seperator filter. Everything is new and apparently clear. Its been a issue since I finished the boat, I just didnt realize it, there were other issues I had to fix. Now that there fixed I hope this is the last one. I might have a vacuume gauge at the shop, I'll have to check.

[gfinch]

Fuel delivery= Pressure, volume and vacuum and like Al said a piece of clear hose to watch for air bubbles. The Vacuum Guage is a tool that will help when used. Used to be the only test device people had when we were called Grease Monkeys.

Al, wish I had work!

[Gorilla0178]

Well I completly disassembled the fuel system today, drained all the hoses and made sure they were clear. Took the pump apart again, all seems ok inside it. I took the pulse limiter valve off the block to make sure it was clear, it was. The pulse coming from the motor is real strong, the valve cuts it in about half. The pump just aint pumping fuel, I removed the hose to the top carb and no fuel is coming out of it while running. Not sure exactly what isnt working but it's just not pumping, it clicks away but no juice....... Looks like I'll be rigging a fuel pump.

[Gorilla0178]

WELL I hope I dont need to get a electric pump yet..... I did some more work to the stock pump, found the 2 piece casing that holds the fuel diaphram was coming apart on one side, very little but there was a small gap between the 2 pieces. I got them back together and I also reinstalled the little piston that pumps oil, and its pumping LOTS and LOTS of fuel. Im not sure which thing fixed it. (I hope its fixed) I can only speculate that either the gap or the piston being removed didnt allow the diaphram go back forth in a straight line, causing it to pump less fuel. I'm not sure how long it will last, but for now I'm going to test it out. I'll keep posted. At least if I need a electric pump I know exactly what I need........Thanks for all the help

[norskarkansas]

I had similar problems with my 225 Venom. I installed a Holley 7psi electric pump in the boat and bypassed the original pump. No more surging. When I bought my motor the VRO part of the fuel pump was already removed. I'm thinking that when they blanked off the hole where the VRO pump had been the function of the fuel pump was messed up. I also tried a smaller 25gph pump from Autozone, but that one didn't pump enough and the motor was still surging on WOT.

[Gorilla0178]

Hope to test it today, the Holley is next.....

[Gorilla0178]

No more surging for now. Went for a run this evening and all was good. Ran great, had fuel all the time, no problem. I hope it lasts. Not sure exactly fixed it but for now its working. I'm not going to mess with it anymore unless it stops working. Now I need to swap out the lowers again and get a prop. Lesson learned... dont remove parts even if you think it doesnt need to be there.

[baja200merk]

Glad u didnt go buy a power pack :D

[Gorilla0178]

Me too.......I hope it keeps working

[kimswang]

This thread is most interesting. I have two of my motors running the surge dance like described in the initial post. I have Holley pumps on all three but have mounted them slightly different than usual. I mounted my pumps where the VRO used to be. The mid used to spin easily up to 6000 but the two outher motors will for some odd reason not run like they used to before the mod to three engine setup. I have fuel pressure gauges though and it looks good from looking at the dash, with the exception of the RPM.... Maybe I have similar problem....

More things to check coming my way....

[Gorilla0178]

Hope you get it worked out. I've learned volume is more important than press, so make sure they all are getting plenty of volume. And check for restrictions.

[racer]

Holley pumps are meant to push fuel not pull.

[JohnR]

For sure. That's why they are mounted back by the tank in an automotive application. Generally speaking, electric pumps are better at pushing than pulling.

John

[kimswang]

Holley pumps are meant to push fuel not pull.

I realize. But I decided to try it out and for the mid motor it is working just fine. That is why I have my doubts about the relevance of my pump placements. Everything else remains the same between all three motors..

[kimswang]

Holley pumps are meant to push fuel not pull.

I've been thinking about this for a while for now. My boat has three of them V8's on the back and the mid ran fine with the Holley pump mounted on the motor. The outer two on the other hand not so much. I could never get them above 4500 RPM's. The only difference between the mid and the outers is that the mid has medium bore carbs and the outer has big bore carbs. Do you think this can have been my problem all along?

[racer]

May not be jetted right but the outside engines are mounted higher thus the pump may need to pull fuel up an extra couple inches and it just wont.

[kimswang]

Thanks for replying Racer. The jetting remained the same but the pump setup changed. I will relocate my fuel pumps to right after the tank and see what happends. The 2" difference might have made the difference but I am leaning more to the difference in carburator size. Time will tell, thanks for having my head spinning for a few days.... :)

[ar300johnson]

kimswang, when I was running big bore carbs on my ported Monty V8 motor, I had to use an Aeromotive fuel pump to get the fuel volume to prevent surging. The blue Holley that worked fine on the mid bore carbs on the basically stock powerhead did not provide enough fuel for the big bores on the modified powerhead. If your rpms remain low, you might need to try a higher volume pump than the Holley.

[powerabout]

have you tried a piece of clear hose as a return line from the motors to see that your fuel pressure is not air/fuel pressure?
It will also tell you how much spare volume you have at that pressure when you throttle the flow

[kimswang]

kimswang, when I was running big bore carbs on my ported Monty V8 motor, I had to use an Aeromotive fuel pump to get the fuel volume to prevent surging. The blue Holley that worked fine on the mid bore carbs on the basically stock powerhead did not provide enough fuel for the big bores on the modified powerhead. If your rpms remain low, you might need to try a higher volume pump than the Holley.


Good info, and very interesting. This might have been my problem all along. I will definately move my pumps from the motor to the boat, near and below the fuel tank. Hopefully this will delay my teardown and rebuild for another year as that was next on my to do list...

[Gorilla0178]

WTF!!!!!!!!!!!!!!!!!!!! I thought I had it all fixed, had a few weeks of good running and today I took it out for a test run with a borrowed prop and the fuel issues popped its ugly head up again. I came home and looked at it, and its pumping fuel, just not as much as it was before when I "thought" it was fixed. Dave (shadow1986) was with me and mentioned (as a few people have) that it looks like a long run of hose to the motor. He suggested a primer pump to feed the motor pump. Thats cool, but what would make it go away and then come back? I'm giong to pull the pump of and check the inside again. He said i could borrow a pump to see if that works. What a Pain it the azz.....

[ar300johnson]

Looks like its electric fuel pump time.

[Gorilla0178]

Thats what I'm thinking, I still want to pull the mechanical one apart again. This sucks balz

[Gorilla0178]

Well I pulled the pump apart, and once again the 2 piece plastic casing that sandwitches the diaphram was coming apart again. I snapped it back together and reassembled it, now it pumps lots of fuel. I'm not going to bother with this to much longer so I ordered a electric pump to put in. Already have the relay wired and relocated the fuel filter so the pump can go where it was. Should have done this awhile ago.

[Gorilla0178]

Ok done with the stock pump, got the new electric pump installed, and it seems to be working good. I have it regulated to 4psi, its hooked to the kill switch so if the lanyard gets pulled the motor stops and the fuel pump shuts off. Its a little louder than I thought, and as usual, after I got it in, I realized another way to install it, oh well it is what it is..... I added a T with a plug, just incase I ever need to pump the tank or something, just because....