Outboard bogging down

[Brendanpd28]

Hey all,

   Hoping to rack the brains of the mechanics out there. My 1990 Evinrude 88 spl has been running great until a snafu today. Hopped around to local coves all day without issues. Idled great at 700 rpm and WOT at about 5100 rpm at 30 kt. Then on the final trek home I was cruising at about 2200 rpm and out of nowhere she bogged down and cut out on me. Showed signs of flooding so I manually opened the throttle and turned her over with no success. Hailed Harbormaster and they gave me a tow back to my slip. I removed all 4 plugs which were fouled for sure. Cleaned them up, checked the fuel filter, and after several turn overs holding the throttle open she started up. Ran her for awhile and all seems ok now. I'm going to replace my plugs of course but I'm sensing a carb issue here?

[boatnamesue]

It sure could be.  I'd confirm proper function of fuel pump before tearing down the carbs.  If you're having to open the throttle plates all the way in order to get engine started means the mix is too rich, hence the fouled plugs.  How about checking your idle mix screws, make sure they don't need to be turned out to lean out the mix.

[Brendanpd28]

The 88 SPL does not have mixture adjustments.....they are fixed high and low jets. During a fill up, my buddy put in enough oil for 20 gallons of gas but the tank only took 16.7 gallons (issues with sending unit accuracy).  So the mixture was already rich which probably started the fouled plug issues.  During the next fill up I added less oil to try and lean things out a little.  I will change the plugs and do a sea foam treatment before I bother with a carb rebuild. 

Thanks 

[Uncutproducts]

Have you ever rebuilt fuel pump? My 88 spl was doing the same thing and was a twofold problem. Carbs were loose, which I never even thought to check and fuel pump had never been rebuilt. New rebuild kit has ethanol proof gaskets and membrane, old one was perforated and on last legs. Ended up replacing all lines under cowl and to engine with ethanol rated hoses, haven't had problem since.

[Brendanpd28]

I believe the fuel pump was rebuilt but I don't know that for sure.  How can I determine that? I have done a lot of outboard repairs to older RUDES and JOHNSONS over the years but never a fuel pump.  Thanks for the help guys.

[Uncutproducts]

Not sure how you tell. Kit is only $20 or so and pretty easy to do. Fuel lines under cowl a little more of a pain but also worthwhile.

[boatnamesue]

The 88 SPL does not have mixture adjustments.....they are fixed high and low jets. During a fill up, my buddy put in enough oil for 20 gallons of gas but the tank only took 16.7 gallons (issues with sending unit accuracy).  So the mixture was already rich which probably started the fouled plug issues.  During the next fill up I added less oil to try and lean things out a little.  I will change the plugs and do a sea foam treatment before I bother with a carb rebuild. 

Thanks

Most stock carbs on outboards have fixed A/F jets, however, an idle mix screw allows you to fine tune the mix.  It is possible your carbs do not have this feature.  "Rich" refers to the engine using too much fuel and too little air, "lean" refers to the opposite.  For example, if my engine were running rich I would turn out the idle mix screw on each carb, thereby allowing more air to enter the carb (leaning out the mix). 

Oil doesn't play a part with a "rich" or "lean" engine.  Those two terms are associated with fuel and its interaction with air (combustion).  The extra oil your buddy added won't harm the engine, but it could be the cause of your fouled plugs.  Actually, he might have done you a favor.  It's very common to decrease the oil-fuel ratio as 2 strokes get older....for instance, running 50:1 instead of the usual 75:1 or 100:1.  The higher concentration of oil in the fuel keeps older engines well lubed.  So I'm told.  Until you burn through this tank of gas you'll continue to notice fouled plugs, smell of fuel, and possibly even more smoke than normal. 

With all this said, I don't believe the event you experienced is due to the plugs or the higher oil-fuel concentration. 

[Brendanpd28]

Thanks for the input. I do understand the lean and rich meanings. Like I described, the fouled plugs were most likely caused by the additional oil. I do believe fouled plugs are what caused the issue since once I removed them, cleaned them, and reinstalled, she started back up and idled at proper rpm. I am curious why you say fouled plugs would not cause this issue though? I am going to perform a sea foam cleaning treatment and install fresh plugs. I already added the proper amount of additional gas to even out the ratio so I wouldn't just deal with it until the tank was empty. Carb issues could also be a contributing factor here of course. I am more trying to figure out if it's worth disassembly and rebuild.Thanks.

[boatnamesue]

I am curious why you say fouled plugs would not cause this issue though?

The extra few ounces of oil that was accidentally added is not a significant amount.  You could double the fuel-oil ratio, from 100:1 to 50:1 or 50:1 to 25:1, and the plugs will continue to fire as normal. 

[Brendanpd28]

I hear ya....was just a little confused because of your earlier comment "the extra oil your buddy added won't harm the engine, but it could be the cause of your fouled plugs."  The break in mixture of this outboard was originally 100:1  so I know a little extra oil is not gonna hurt anything.  I have just seen this lead to gummed up carbs and fouled plugs so I assumed that could've been my issue.  Even though I already got her started and idling again i will still clean out the internal engine components as best as possible with a sea foam treatment, change out the plugs,  and check the fuel filter  before I take her for a test run at WOT.

[boatnamesue]

I hear ya....was just a little confused because of your earlier comment "the extra oil your buddy added won't harm the engine, but it could be the cause of your fouled plugs."  The break in mixture of this outboard was originally 100:1  so I know a little extra oil is not gonna hurt anything.  I have just seen this lead to gummed up carbs and fouled plugs so I assumed that could've been my issue.  Even though I already got her started and idling again i will still clean out the internal engine components as best as possible with a sea foam treatment, change out the plugs,  and check the fuel filter  before I take her for a test run at WOT.

It is possible the additional oil fouled the plugs, despite the additional oil not being harmful to the engine.  The question is, does your engine burn the additional oil.  And I can see how this can be confusing.  Let's say you doubled the oil and noticed no difference with engine performance.  Then id say no prob.  Same scenario, but poor results, id say resort back to normal oil concentration.  As I previously mentioned, some older 2 stroke engines perform better with more oil.  Just don't know till you try. 

[JimInPB]

My 1987 88 spl runs on 50:1 all the time.  I go several hundred hours between spark plug changes.  My plugs come out looking tan & normal.  Mixtures as thick at 50:1 are not a problem, even for prolonged running at modest speeds.

Basic troubleshooting for V-4 crossflow motors with 2 power packs is as follows:

Both top or both bottom cylinders cut out &/or bog at the same time - check fuel feed to that carb bank

Both right or both left cylinders cut out &/or bog at the same time - check power pack on that side, could also be the pickup under the flywheel or wiring or a bad tachometer.

Single cylinder cuts out &/or bogs - check coil, check ignition wire, then check for stuck float valve.

All 4 cylinders cut out &/or bog, if plugs are dry, check fuel feed & fuel pump.  If plugs are wet, check for dead ignition switch, short in ignition kill circuit or overheat sensors killing ignition.  Could also be problems under the flywheel. 

Air leaks (loose carbs) cause a lean condition, not rich.  The plugs often come out bright white & engine damage often happens.

If one plug is dark & the rest normal, then either you have a serious mixture problem on that cylinder, a stuck float valve, an ignition problem on that cylinder or low compression on that cylinder.  On rare occasion, I have seen a jet fall out.

A really funny looking plug with crusty stuff on it, is often a sign that water from the cooling jacket has made it's way into the cylinder & can be very bad news in some cases.

[RickK]

Nice set of troubleshooting guidelines Jim