Help please. Motor woes 1991 Johnson 115hp on my 170

[aviator8]

I wonder if some of you might be able to help me diagnose my problem. I just recently purchase a 17ft CC with a Johnson OMC 1991 115hp 2 stroke. Model number VJ115TLAIE. What I am experiencing is dificulty getting the motor started sometimes, and cutting out while idling, both in gear and out of gear. Here are the symptoms I see:

This unit has VRO. Once I start up there is no issue while running at speed.


When I come to rest and leave the motor in idle it will idle fine for awhile. 10-15 mins. Then I get an ocasional chuggin sound. The best way I can describe it is like the unit is huffing or sucking air. This will be followed by a stall shortly if I do not increase my throttle up to around 1000rpm. Normal idle speed is about 700RPM


When i turn off the engine after being run for 30 mins or so. If i have it off for any period longer than 5 mins I have to choke it to get it started

I also am not able to just start it up in the netral position. I have to advance the throttle in neutral to get it started, then let it run at 1500rpm for a few mins before it will idle

When i do the start procedure above I notice that there is alot more oil smoke than normal, but once idling the smoke level seems normal.



I would think that after running at speed for 30 mins the engine should be warm enough to just start without choke, and without having to rev it for sevral min just to get it idling. Am I off base or do any of these symptoms point to things I can check/adjust to get this thing to start easier and maintain and idle?

[RickK]

What year 170?
Reason I ask is that the ethanol in the gas now may have loosened up some crud in your fuel system and it's clogging your carbs up.

Do you have a good fuel filter on the fuel line?  10 micron?

[aviator8]

The boat is a 1976.  The boat has had this same motor on since the early 90's so i don't think it is an issue of loosening up residue in the fuel tank.  It has a fuel filter but no idea if it is 10 micron.

[slvrlng]

I read on another forum the E-10 was eating the inside of the older fuel lines. You probably need to replace them just like I do. Have you done a decarb with seafoam yet that should get you a good starting point. The VRO adjusts the amount of oil each time you start it. It is an air driven pump that works off the pulse of air coming through the reeds. When you crank it it pumps more oil to load the pistons up so they don't bind. Then it backs the ratio off as rpms increase. What kind of compression do you have and do you have pretty equal numbers on all cylinders?

[RickK]

The boat is a 1976.  The boat has had this same motor on since the early 90's so i don't think it is an issue of loosening up residue in the fuel tank.  It has a fuel filter but no idea if it is 10 micron.

That's exactly why I think it may be ethanol.  Ethanol is a solvent that will loosen everything up in the tank and the fuel lines. The engine may be 90's but the tank (and maybe line) is 70s.
My engine started running weird the last time I ran it and I had only a water separator on it for 20 years.  A few months ago I put on a filter and took off the separator - now I'm reading I should have both.  Here comes another hole in the transom  

[GoneFission]

Idle jets clogged - could be the ethanol, or dirty gas, or ???  These days, everyone needs a good fuel filter with a water separator feature.  Don't worry so much about micron size, just get a good filter/seperator and use alcohol-resistant hose downstream.  Not a bad idea to replace the hose upstream if you can get to it.  

Either way, you need to drain the carbs and blow/clean any residue out of the idle jets.  The residue from ethanol breakdown is like little clumps, it's not like a varnish build up.  Once you get the carbs clean, adjust them for mixture and idle according to the manual, and you should be good to go!  

See ya on the water!

[bdtsr]

As previously stated:
Ethanol, fuel lines, clogged low speed needle. Also sounds like your floats are shot allowing fuel under pressure flood the carbs and engine. After 30 minutes or so the fuel evaporates but requires the choke (actually a primer system) to start. This is like a vapor lock/fuel boil over.

The water seperator actually has a filter inside it. Install the Racor 10 micron replacement with the site bowl on the bottom this way you can SEE the water and drain it. The Mfg's are now saying to use a stabilzer with every fill up.

OMC's VRO system originally varied the amount of oil in the fuel to the engine (the Variable part) but then switched to a straight 50:1 ratio. At idle the original pump would mix as high as 100:1 but 50:1 over about 1500 or so rpm. They changed this with the VRO II (I believe). Problem was, after prolonged idling and punching the throttle the motor would be running at full throttle on 100:1 ratio, not good. The system never backed off the oil only increased as rpms increased. The Vro was also part of the fuel pump mixing the gas and oil before it left the pump. If the oil part failed it would pump MORE oil not less.

[aviator8]

My fuel lines are all alchohol resistant.  Just went out to the boat and checked.  I just read up on the seafoam decard and that sounds like a plan.  I am going to try to find some locally.  I just ordered the service manual for this engine and will replace the fuel filter fueal water seperator,  seafoam it, and see were it stands.  I haven't checked compression but will probably check that also.  If this gets me nowhere I may have to do a carb rebuild.  I'll let you know what happens.  

Keep the sugestions coming if anyone thinks of something else to check into.

Thanks
Scott

[RickK]

Discount auto has Seafoam.

[aviator8]

OK did some things and found some not so good news.  I replaced fuel filter, had a problem with a plug wire and replaced that.  Did a compression test for a baseline.  #1 is 85psi  2-4 are 110psi, so not good news.  Did a seafoam decarb hoping for a sticky ring but no luck there.  I got the same compression readings after a decarb.  I sprayed some fogging oil in #1 and retried compression test and it climbed 10psi to 95psi so that tells me there is probably a ring issue or worn cylinder and not a head gasket.  

Think I am going to nurse it through till winter and then pull the head and see just what I am dealing with.