93' Johnson 70 HP Fuel Pump

[digidog00]

I recently bought a boat with a 93' 70HP Outboard (With Carburetor). Since I got it, it has been running rough. Stalling when put in gear, when idling, and wont go past 3000 RPM. I have had it checked by a mechanic several times and they found some electrical issues that was causing start problems but this issue with stalling, etc persists. I decided to dig in to the fuel system and found that the fuel pump has the electrical line cut. I have a primer ball which checks out ok but when I checked the fuel pump, no fuel would go thru when I cranked. I am thinking I need a new fuel pump and per the Johnson parts list it is supposed to be electrical. Main questions are, Is there some reason someone would cut the electrical line? Should i replace with an electric fuel pump per the OEM specs? With no power, would an electric pump work like a mechanical? I am about ready to dump this engine if I cant figure this out. Any thoughts/advise would be appreciated. Thanks!! OEM Part Number for the Fuel Pump is: 0435560 FUEL PUMP ASSY. $484. Would hate to go by a OEM replacement for $400+ if this isn't likely the problem.

 

[Daviet]

Re: 93' Johnson 70 HP Fuel Pump

Welcome to the forum.
I think you are talking about a VRO pump, which mixes the fuel and oil for you. Are you running premix fuel or do you put stright gas in the tank and oil in another tank?
If you are running premix, the cut wire is for the alarm and has been cut when the owner started to use premix fuel. You engine was not produced with an electric fuel pump.
You could still have a fuel pump problem, the fuel side of the VRO pump will work if the oil side is bypassed.
It sounds like you could have some carb problems, stalling and no high rpm's, might be time to overhaul the carbs.

 

[phillnjack2]

Re: 93' Johnson 70 HP Fuel Pump

what is the model number of your engine ?

 

[digidog00]

Re: 93' Johnson 70 HP Fuel Pump

Thanks for the Welcome!! Yes, I figured out yesterday it was the wire for the oil primer. Still think the fuel pump may be bad as when I removed the output fuel line and cranked nothing came out. If not that then next on to cleaning the carbs. I have to check the exact model. I thought it was J70TTLETS but now wondering if maybe it is actually a 92 engine Model VJ70TLEND. Keep forgetting to right down the actual model number. Will let you know what I find after the carb job. Hope that solves it once and for all. Thanks!!

 

[AlTn]

Re: 93' Johnson 70 HP Fuel Pump

try maxrules.com for info on rebuilding the fuel pump only side of the vro if that is deemed necessary

 

[digidog00]

Re: 93' Johnson 70 HP Fuel Pump

UPDATE: Well, I rebuilt the fuel pump, installed a new fuel filter/separator, and cleaned the carbs. This was done by a mechanic and it is still doing the same thing!! The mechanics have given up. I just cannot believe this....how hard can it be. Engine rev's fine in Neutral but still will not go past 300 RPM when full throttle. Mechanic thinks one of the pistons has spark but is not firing. No signs of a blown piston or o-ring.....Any more ideas? Worries me when seasoned mechanic gives up. Timing is good, compression is good, etc....HELPPPPPPPP

 

[Floridasportfisher]

Re: 93' Johnson 70 HP Fuel Pump

UPDATE: Well, I rebuilt the fuel pump, installed a new fuel filter/separator, and cleaned the carbs. This was done by a mechanic and it is still doing the same thing!! The mechanics have given up. I just cannot believe this....how hard can it be. Engine rev's fine in Neutral but still will not go past 300 RPM when full throttle. Mechanic thinks one of the pistons has spark but is not firing. No signs of a blown piston or o-ring.....Any more ideas? Worries me when seasoned mechanic gives up. Timing is good, compression is good, etc....HELPPPPPPPP

I am experiencing same symptoms with a 98 70hp Evinrude. The bottom cylinder was being flooded with gas causing the engine to surge and run poorly. I am replacing the VRO pump with a conventional diaphragm pump. OMC #438559 around $75. to $100.00 for a new one. Make sure you connect the two out lines correctly it makes a difference. One is the pulse line going to crankcase the other to carbs. Of course the plastic piece on the front is where you connect fuel line from tank. Picking up pump tomorrow tech is going to show me which lines go where! Hope this helps!

 

[phillnjack2]

Re: 93' Johnson 70 HP Fuel Pump

could be powerpack stuck in slow mode !!!!!!!!!!!!!!

 

[Floridasportfisher]

Re: 93' Johnson 70 HP Fuel Pump

I took the VRO pump off and installed a temporary 5 psi 12 volt electric pump, capped off pulse hose, runs like new!! Will pick up the OMC manual pump today and finish the job.

 

[digidog00]

Re: 93' Johnson 70 HP Fuel Pump

Replaced the powerpack already. Did solve an issue with starting but that's it.

 

[digidog00]

Re: 93' Johnson 70 HP Fuel Pump

Thanks. I did a rebuild of the fuel pump side of the VRO. Has not made a difference. Idles a bit better but that's about it. Mechanic said the old one seemed fine as well.

 

[AlTn]

Re: 93' Johnson 70 HP Fuel Pump

do you have an ir thermometer to check the head temps around each sparkplug area after running ?..if so, are they the same?..if not, do they feel the same just from touch?....running w/o the cowl and carb cover, can you look into each carb throat and determine that each has a similar spray pattern?..have you tried a cylinder drop test to check that each plug < cylinder > is firing?..an inductive timing light on each plug lead to determine you aren't losing spark?...all this to say that what you are describing sounds like one cylinder isn't doing its share

 

[digidog00]

Re: 93' Johnson 70 HP Fuel Pump

Yeah, it does seem one cylinder is not doing its share. What could cause this? What steps could I take to check this out further? Mechanics still scratching there heads. Say there gonna take it out and sink it...LOL

 

[digidog00]

Re: 93' Johnson 70 HP Fuel Pump

How did this work out for you?

 

[Floridasportfisher]

Re: 93' Johnson 70 HP Fuel Pump

How did this work out for you?

I noticed the bottom carb was leaking gas out when the bulb was squeezed. I removed cylinder head top and center cylinder were firing properly, while to bottom cylinder was washed and appeared to be flooded with raw gas causing it to lose it`s oil and start wearing on the bottom of cylinder wall. I consulted my OMC mechanic and he said it was common for the VRO to malfunction and dump raw gas into the power head. I remove the VRO pump, plugged the pulse line and installed a 12 volt electric 5 psi fuel pump in line between tank and carb. Motor fired up immediately, idled smoothly, and had quick response on throttle. I came to the conclusion the VRO was junk and discarded it. I purchased an OMC diaphragm pump for $65.00 at my local marine parts store. You will need the one that has two nipples as well as the one that hooks to your tank line. One hooks to the pulse line going to power head while the other goes to carbs. You will have to fabricate a bracket to attach it to the power head. I did the install as well as new head gasket, put her back together. Again she fired right up. We headed to our local boat ramp and slid her in the water. Hit the key, just bumped it, she fired right up. I put her in gear throttled up and wow! took off like a rocket and ran better than it ever had. My problem is solved! I tried to post pictures of the install but failed at it. If you will e-mail me at floridasportfisher@gmail.com will send you pictures.