yamaha F115B four stroke: excessive white smoke

[andywilk]

I own a 2003 yammy 115 4 stroke that is acting odd. It has excessive white smoke in the exhaust, really bad at start up. On a still day, after I've run the boat I continue to see the white smoke in small quantities coming out the exhaust 5 minutes after I shut the motor off. Also the last 3 times out I've had problems starting after I've run at WOT for about 10 minutes and then stopped for a while to fish. On restart the engine cranks but doesn't start and the white smoke appears. This has happened once on each trip, but I have numerous successful restarts on those same trips(use the boat to fish, moving form spot to spot at WOT, 10-20 minute transit times and then motor off 10min- hr fishing). The restart problem seems to go away if I wait long enough, and I've advanced the throttle in neutral. Also 2 trips ago the engine overheat alarm sounded and the boat powered down, seems like the engine cover feels hot compared to past but that may be my imagination. Not sure any of these are related, but this engine has been superb until recently and I'm worried about the ways its now performing.

I have the boat serviced every 100 hrs/yr. I did let the oil get low 2 years and had the overheat alarm go off but immediately got it in to the dealer, they said there was no damage to the engine after they ran all the diagnostics and inspected it. I run it at high RPMs much of the time and have about 400 hrs on it.

I took it 2 weeks ago to the dealer and reported all this and had it serviced. Took it out yesterday after putting in fresh gas and still had excessive white smoke and one problem with the restart. The dealer could not find a fault showing the recent overheat alarm and said the white smoke was a bad plug. I'm worried something bad is about to happen, like water in the cylinder or bad fuel. I just shelled out $400 at my dealer with no answers, I've got any extended warranty that expires in a yr. Any ideas.

 

[jevery]

Re: yamaha F115B four stroke: excessive white smoke

Couple of questions that may help someone with more knowledge than myself narrow it down. Does the exhaust smell like oil and did your shop do a compression test? I?d think the bad plug would warrant a closer look at that cylinder.

 

[yamamarinetech40]

Re: yamaha F115B four stroke: excessive white smoke

Have to wonder what you call 'white'....oil doesn't make white smoke, it's bluish...steam is white, but it's not smoke....smell would help....only white smoke i've ever seen was transmission fluid and you don't have any here....so...???
If it's steam...and that wouldn't surprise me hearing how you've abused the engine, running it hot enough to go into RPM reduction and running it so low on oil it overheated(?)....you may have steam from cracked block, head, who knows? Can't give advice if don't have numbers(compression on each cyl, leakdown, etc....) Just to have dealer put it in water WITH YOU and observe what YOU see...

 

[andywilk]

Re: yamaha F115B four stroke: excessive white smoke(steam)

Re: yamaha F115B four stroke: excessive white smoke(steam)

Its steam, no odor. I took it to the dealer to have it checked out and they did compression test and everything was within spec. I've read several references to the leak down test, is that for oil, water etc... what does it check for.

 

[Yamajoe]

Re: yamaha F115B four stroke: excessive white smoke

The overheat problems have not been rectified: remove the thermostat and PCV, check and clean, replace if they look/test suspect; i would also recommend putting new water pump kit in as as well if this has not been done. As a general rule you should be able to hold the open palm of your hand on the side of the motor for 30sec without it being too uncomfortable (watch for those moving parts); the leak down test can pin point the source of your compression loss, but if the compression test numbers are to spec. then isolate your cooling system first.

 

[yamamarinetech40]

Re: yamaha F115B four stroke: excessive white smoke(steam)

Re: yamaha F115B four stroke: excessive white smoke(steam)

ok, so now we know no smoke, steam....i suspect you have water getting into the combustion chambers....easy way to tell is pull the sparkplugs. I don't think you are still overheating, you didn't say anything that makes me think so....if the plugs have any sign of water, you'll know....you know what water looks like...so run the engine a little, not till very warm just a little and check the plugs...also look for plugs having a very clean look, should be black on threads and away from spark, not greyish silver...greyish silver is steam cleaned, get it? Once you've found water we'll go from there....

 

[andywilk]

Re: yamaha F115B four stroke: excessive white smoke

thx for the advice...had the water pump replaced at the2007 service.... I'll check plugs