1987 50 hp not idling

[Whitefeather1968]

I've got a 87 model 50hp (J50tlcud) that's got me worried. A couple of weekends ago I took it out and ran it after about 4 mos. of sitting in the garage. It ran fine but, after about 30 mins. of WOT it started bogging down. I would choke it and it picked up then bogged down again. After about 10 or 15 minutes of choking it, it ran fine intermediately. It would idle fine just not run wide open. So I get home and spray Seafoam in the carbs and put Startron in the gas tank. Seemed fine but took it to a friends pond to run it in the water but left it on the trailer. It started fine, idled fine, and revved up fine with the high idle.
Took it to the lake the next day, it started fine and ran at WOT for about 30 seconds then it really started bogging down, and would not run at anything below half throttle. It would run after choked for a few seconds. Finally got it to WOT and went to the Marina and bought 2 cans of Seafoam (32oz.)for 12 gallons of gas. Took off and got it to WOT and it finally pepped up and ran fine for about 45 mins. Except, at low end about half throttle. It still bogged down and would not idle. I bought 2 carb. kits and soaked them in cleaner for 6 hours.It still will not start or idle without choking.Now it looks like it may be a fuel pump issue, because the filter housing is about 3/4 full until it starts with choke then dies and the fuel is gone. I'm still hoping its a carburetor issue, but they are as clean as I can get them.
I have cleaned and rebuilt both carburetors with compressed air and cleaner, cleaned the fuel filter, replaced the hose and primer bulb, including the connection at the engine, drained the fuel tank and replaced spark plugs. I will do compression tests tomorrow.
I disengaged the VRO and run mixed fuel using factory oil at 50:1 ratio. I would like to replace the VRO with a regular fuel pump but don't have the know how. Dealer I talk to said it can't be done and that the VRO/ fuel pumps can't be rebuilt.
Right now I'm a little perplexed as what to do next.
Any suggestions are greatly appreciated as I can't get it to run long enough the check timing or see if there is a vacuum leak some where.

 

[ondarvr]

Sounds like the carbs are still dirty. Did you completely take them apart and clean every passage way?

 

[Whitefeather1968]

Yes, even pooped out the caps and blew the jets out and replaced them. I will redo tomorrow. How long can I let then soak in parts cleaner? Can said 4 hours and I let them soak for 6 before blowing them out.

 

[lmuss53]

I agree with ondarvr, you still have dirty carbs.

Don't go back to that mechanic, he is full of it .

Although I believe you have a carburetor issue the OMC pump to replace your VRO pump is a part #0438559. There are also rebuild kits available for the entire VRO pump and for the fuel side only. The easiest and least expensive way if the pump fails is to replace the pump with the one I listed. There are many threads about removing VRO.

Having said that I think you still have debris in the carbs.

Make sure that you see through every possible passage, something is hung up somewhere, possibly still coming in. Do you have the newer ethanol safe hoses, if not they could be crumbling from inside recontaminating your clean carbs?

Look to the small primary jets, it sounds like the secondary jets are open. If you use the canned air watch and see that you blow a little of the cleaner through each opening, that you have flow through the port.

 

[Whitefeather1968]

You guys are awesome. I'm gonna redo them tomorrow and try it again. I hope you are right.

 

[Whitefeather1968]

I replaced some of the hoses a couple years ago but, was planning on that again. Thanks for the info.

 

[lmuss53]

If you have any of the old black hoses they need to be replaced by the gray or ethanol safe stamped hoses. I had to change every hose on my old 55 after cleaning the fuel system and carbs about a half dozen times. If you see little black sandy looking flecks inside carbs anywhere that is the problem. I also have an OMC fuel filter inline on all my motors just before the carbs.

I gotta say what a great engine I thing that 2 cylinder OMC motor is. MY old '76 55 just purrs like a kitten and pushes my pontoon right along at 20 mph. I have a newer 1990 50 hp model ready to go on to get the tilt trim option on the pontoon, but I have a 17 foot Blue Fin waiting for the 55.

 

[oldboat1]

^^Agree with all. If the motor is running, a standard test for fuel pump issues is to use the bulb when the motor is acting up. If operation improves, points to a fuel pump problem.

If you can keep it running, check temperature (top of head should be warm, not hot). Should see a stream at the tell tale, but should still check temp. Along with the planned compression test, I would do a spark test (look for a strong 1/2 inch spark, using a tester).

 

[Whitefeather1968]

Oldboat now that you mention it I did notice today that it did feel hotter than normal and the overheat alarm did come on the other day for about 5 seconds but, i attributed it to motoring at lower 1/3 throttle to open the low end jets up to the Seafoam. Water stream looks good because I've made that mistake before of testing it in driveway and forgot to turn water hose on so, I keep a close eye on it now even in the water.

 

[racerone]

If you have run it without water then you need to install a new impeller.--And the place to mount a conventional fuel pump is already there on the side of the top cylinder.

 

[juno pierrat]

look for this fuel pump, 0438556 - Fuel Pump , gasket 0303615 - Gasket and 2 screws 0314417 - Screw. these part are for a 87" 48spl
you will have to plug the pulse hose that goes to the old VRO.
if you removed the core plugs during your cleaning those little holes under it need to be poked with a small wire to insure there open, they can still be reached through the carb throat if you don't want to remove the core plugs again

 

[Whitefeather1968]

No Title

I may be onto something....this morning I was putting my boots on and looked down and found this laying on the floor It looks like a jet to me but, I don't know where it came from. I've looked at the schematics and see two jets that are removable, the one in the float bowl that you access through the bowl drain and the one at the rear of the top piece just above the air inlet that I assumed to be the low speed jet.Is that correct? I did not turn any jets because I don't have the right tool. Could it have blown out when I hit it with the air compressor and didn't know it? I looked at the 2 carbs again and can't seem to figure where it might have come from. Sorry for the blurry images.

 

[racerone]

That would be an idle orifice.----They should be in tight.---------I guess some folks still think these things need to be out 1 1/2 turns from seated .---Then they fall on the floor during cleaning.------A small screwdriver will put them in.--No need for a special tool here !

 

[Whitefeather1968]

Holy Cow!!!! I guess it's better to be lucky than good. To find it at 1:30 in the morning about 20 feet from the work bench is proof of that. I just need to find the other one now and replace the hoses and try again. Thank you for the help.

 

[Whitefeather1968]

OK day 2 results, Followed everyone's advice found 2 new low idle jets had them installed, replaced all the fuel lines, replaced the VRO pump with standard fuel pump, replaced the fuel filter, did a compression check with both cyls. at 120 psi, replaced the roller assembly on the throttle arm, and went through the carbs again and had a mechanic look at them and he said they were good. Did the hand test on the block and it was fairly cool so did not address the impeller issue.
I hook it up to muffs and started it up,Sounded different like it was skipping. Would not start without choke. After several attempts to get it going, all of a sudden it revs way up and I noticed a lot of raw gas coming out of top carburetor. As soon as it would burn all the gas out it would die. As soon as your move throttle or high idle it bogs down and dies. Will not run without the aid of the choke for maybe 10 seconds and that's at a very low idle.
A couple of things has me wondering... is the adjustment between the flywheel timing advance and the carburetor out of adjustment and maybe the top float is set too low. I have it set to be perfectly level with about 1/8 gap between the bottom of float and top of bowl housing. I did notice when I took it apart originally the float was set a little lower than it is now. The new in line horizontal fuel filter is not set perfectly level it is set more like a 45 degree angle and is installed in front of the new fuel pump. Any thoughts before I take it to a dealer?

 

[racerone]

Fact-------Most " carburetor problems " turn out to be something else.--Does spark jump a gap of 3/8" or more on your motor.--Answer with YES or NO.

 

[Whitefeather1968]

Definitely 1/4 inch on both with strong blue spark. Not sure about 3/8 inch.

 

[lmuss53]

If it was running before, the timing did not change itself and I would not mess with that, I would get that float set so it isn't flooding the motor with fuel and see what happens from there. It's probably running rough because it is running on one cylinder while the other carb is just dumping raw fuel as soon as the bowl fills. I would set the float close to where it was before. Do you flip the carb upside down and blow through it to make sure the float valve is closing? The fuel filter should be fine regardless of the angle it is mounted at, on my 70 the white plastic factory filter is almost vertical and works fine.

 

[oldboat1]

couple of thoughts: 1/4 spark isn't enough. Your CD system should produce a strong 1/2 inch spark, measured with an adjustable spark tester (7/16 inch). Start at a half inch or more and work back if you need to in order to see what you have. If your testing shows you have a 7/16 inch spark, you still may be losing spark when operating. The best way I found to check for that is to attach a timing light to each wire while running, and see if the flashing is continuous.

You have the accu mix fuel system on that engine, which you have apparently bypassed. I have not worked with that system, but it appears to me another tank -- standard tank -- might be in order. If you can borrow a working tank, and connect to your fuel pump that might be preferable. Further, the fuel pump may be ready for a rebuild (hole or tears in the diaphragm). A kit is available.

Finally, I am not a big fan of Seafoam. It seems to displace fuel system debris and block up carbs as much as it removes carbon in the cylinders, real or imagined. Additionally, I've never had a issue with setting carb floats (other than installing them upside down once or twice!). With the carb inverted, setting the float level to the eye has always been sufficient in my experience. For carb issues, though, it is necessary to fully disassemble the carb, and soak all metal parts -- then clean and probe with small soft wire or monofilament line, followed by carb spray to flush.

You should run the motor in a test barrel or in the lake, as back pressure is needed.

 

[Whitefeather1968]

I just checked the spark using a wood ruler holding tip of sparkplug 1/2 in. from engine block and got good spark with both cyls. Going to pull carbs off again and start over and readjust float as was before.