86 - 120 HP VRO possible replacement

cdn-pk

Petty Officer 2nd Class
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May 20, 2009
Messages
162
I have a 1986 120HP Johnson J120TLCDC on my 19' Edson Challenger GT.

Problem: started last summer. will be cruising WOT (5200rpms) and all of a sudden it will throttle down to 4800prms or slightly lower. sometimes it does not happen sometimes i can go to idle and then take off again and it'll go to 5200 and stay other times it won't get above 4800 for the rest of the trip.

- i replaced all fuel lines to the tank with 3/8"
- replaced in line fuel filter (been there a couple years anyway)
- checked all fuel lines right to carbs, could not find a leak, plus the primer bulb stays firm.
- spark looks good bright blue and 7/16"
- compression great 115-120psi all cylinders.

So i used it all last summer but it's been bugging me. so here is a brief history of the boat. i am third owner. second owner had it for 15 years never did a thing to it except change spark plugs every year. (and a couple AL props). he said nothing never brought it anyway for any work and all he did was spark plugs from 1996 to 2011. so first thing i did was new impeller.

What i discovered about the VRO on the engine. it is not original (should be part#174304) and has a tag on it labelled VRO2, made in Mexico, alcohol resistant part# 174876 (it is a 3 wire VRO). it seems i can only find that VRO number for 1989 models.

Changes i added a water / Fuel separator. that spring So what i was thinking was that the OLD VRO2 pump might be getting week. so been worried about leaning out the cylinders.

So i purchased and have yet to install all new oil line and primer bulb. (tank kit) brp# 5008617.

My questions are:
1) should i change out the old oil line and try again or should i just replace the VRO with the new 5007423 VRO/OMS pump?
2) any other way to test to determine the fuel pressure at wot? i'll have to wait for summer to run it at wot.
3) should i remove the water fuel separator? (don't like this option but...)

Reason ask is the new VRO has a 4 wire harness and i have to modify the engines 3 wire connections (push the pins out and then re-insert them to a new 4 wire connector and add another wire). basically it seems like there is no going back.

Also premix is not an option, and keep in mind there is no hose to put the ears on, lake or any open body of water) we have four feet of snow so my testing is limited to my garage (heated, thank god).


Thanks guys
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
39,236
Re: 86 - 120 HP VRO possible replacement

The first thing I would do is take the VRO pump off.--------They are surprisingly easy to inspect and repair.----You have time to do this.------Not sure why anyone would rush out and spend $450 on a stab in the dark to fix this.
 

cdn-pk

Petty Officer 2nd Class
Joined
May 20, 2009
Messages
162
Re: 86 - 120 HP VRO possible replacement

i'll pull it off and check it out, and i got a good deal on the new one ($300, brand new with the BRP markings). my concern was of course at least 20 years on the old one, plus the added wear of our freeze thaw cycles.

i'm a busy fellow and our boating season is measured in weeks around here. so i either do preventative maintenance if i want to use it a given year. or pay through the nose if something breaks and possibly damages something else plus lose a season.

i do have a question, can i take apart the fuel side and possible repair without damaging touching the oil side??
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
39,236
Re: 86 - 120 HP VRO possible replacement

You need a #15 torx screwdriver to work on the pump.---They are easy to work on.----There is nothing magic about the oil side either.-Go for it.
 

boobie

Supreme Mariner
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20,826
Re: 86 - 120 HP VRO possible replacement

Better check and see if you can get parts for the oil side before tearing into it.
 

racerone

Supreme Mariner
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Dec 28, 2013
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39,236
Re: 86 - 120 HP VRO possible replacement

There are no factory repair parts listed for the oil side of the VRO------Does not mean it can not be inspected.
 

boobie

Supreme Mariner
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20,826
Re: 86 - 120 HP VRO possible replacement

And if he breaks something while taking it apart, then what ??
 

racerone

Supreme Mariner
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Dec 28, 2013
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39,236
Re: 86 - 120 HP VRO possible replacement

They are fairly simple and nothing will break.-----------------I have taken many apart for inspection and have a box of repair parts.------------Most shops are quick to recommend " buy a new one like everybody else does "
 

emdsapmgr

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Joined
Dec 9, 2005
Messages
11,551
Re: 86 - 120 HP VRO possible replacement

You've got an rpm drop during operation. You seem to be concentrating on a fuel delivery problem. Possible you've got a spark problem on one plug. I'd check to be sure that you've got good spark on all 4 plugwires-once the engine heats up to normal operating temps. You can use an inductive timing light or a cylinder drop test to confirm spark to each plug. Weak ignition components tend to fail once the engine heats up to normal operating temps.
 

cdn-pk

Petty Officer 2nd Class
Joined
May 20, 2009
Messages
162
Re: 86 - 120 HP VRO possible replacement

Thanks emdsapmgr,

i did check the spark with the spark gap tested last fall twice, once cold and another after a WOT run. Both seemed strong and Blue to me. i'll have to wait for the big thaw and i'll try it with a timing light.

When it drops rpm it doesn't get any rougher, just seems to slide down the power band. i'll keep checking out the fuel system for now.... since that all i can do.

cheers
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 86 - 120 HP VRO possible replacement

Once you know it's not a spark issue, you can do a water test. When the engine starts to lose rpm's have a friend constantly pump the fuel hose bulb. This will force extra fuel into the carbs. If the engine runs fine at wot as long as you constantly prime the fuel hose bulb, you've got some type of fuel restriction, even a weak pump. That engine was not shipped/designed for a fuel water separator in the system. You might bypass that till you know just what the problem is... I am a fan of the separators- just be sure it's not part of the problem.
 

cdn-pk

Petty Officer 2nd Class
Joined
May 20, 2009
Messages
162
Well - rebuilts the carbs and found that the port cylinders was not consistently firing (using the Cylinder drop test and with my spark gap tester). There were times when the port side of the head would not get hot (barely warm, 109 deg F). found the stator fine and the coils were okay. Seems the power pack was getting flaky (especially after it was warm). replaced the power pack and everything is back to normalish. Going to put it through some tests this weekend at the lake. i will report back with any other findings.

I did find that in a tank the starboard a cylinders seem to be running 20 deg F hotter... i had the heads off and checked all the passages with weed eater twine, i even replaced the thermostats (they were original, and i got a good deal) nothing really to explain the temperature difference except the port thermostat feeds to the starboard then to the water spout. anybody have any thoughts?
 
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