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CanadianNorth 07-04-2013 09:05 PM

Yanmar 2qm15 smoking in gear
Hi folks,

I recently purchases a Spirit 28 (79) with a yanmar 2qm15. the boat had been on the hard for a couple of years.

The engine has been relative well maintained, and I have changed the oil, drained the fuel, refilled the tank, changed the fuel filers, and oil filter.

the engine starts up in a second, every time. In neutral she rev's well and sounds great.

As soon as you put the engine in gear she struggles, and smokes up quite a bit. After a few few minutes in gear she will pick up power and cruise at 6 knots. But the engine still sounds like she is struggling.

When you throttle back she waivers and nearly cuts out, and then if you slip into neutral she picks back up and revs up. .....

..... I have no idea what to make of this situation. Can anyone lend some advice?


fryewe 07-04-2013 09:23 PM

Re: Yanmar 2qm15 smoking in gear
What color smoke? What do you mean the engine runs "low"? What does "low" mean?

Smoke color vs potential problem is at Diesel Smoke tells YOU a Story…

CanadianNorth 07-04-2013 09:25 PM

Re: Yanmar 2qm15 smoking in gear
When i say the engine runs low I mean it seems like it's struggling a bit and is the rpms are low.

The smoke is black.


CanadianNorth 07-04-2013 09:35 PM

Re: Yanmar 2qm15 smoking in gear
what i find unusual is that, once in gear and after a couple of minutes of low rpms at high throttle and lots of smoke, the engine seems to rev a bit higher and run without smoking.

fryewe 07-04-2013 09:54 PM

Re: Yanmar 2qm15 smoking in gear
Black smoke is soot due to incomplete combustion. Either too much fuel or too little air or the combustion cycle is "broken" by bad timing or poor compression. Since the condition seems to be intermittent I would suspect a fuel injection nozzle may be sticking open spraying excess fuel into a cylinder.

You can do a quick check of the air filter and air inlet to see if you have an obstruction if you haven't already.

A fuel additive can sometimes free up a sticking injector...something like the product "lubricity" (I have no affiliation with the mfr).

CanadianNorth 07-05-2013 06:44 AM

Re: Yanmar 2qm15 smoking in gear

I will try some fuel additives to see if that clears it up. I wouldn't say it's completely random, however. It only happens when you are in gear.

Gladrags1 07-05-2013 06:49 AM

Re: Yanmar 2qm15 smoking in gear
4 Attachment(s)
It sounds like there is something inhibiting your motor from turning the prop. Excessive growth (barnacles) on the prop WILL cause this. During our first sail of the season out prop was so fouled that we had a lot of soot on the transom, couldn't rev more than 2000 rpm in gear. Once cleaned, engine ran normally without soot. I would dive on your prop and check the prop and the shaft for growth or lines wrapped around the shaft or anything that may inhibit its free ability to turn.


Minnewaska 07-05-2013 06:55 AM

Re: Yanmar 2qm15 smoking in gear
Air filter clean?

Could be back pressure from the drive, either a fouled or incorrectly pitched prop, overtightened stufffing box, sticking cutlass or the tranny itself. I would check them in that order.

CanadianNorth 07-05-2013 06:59 AM

Re: Yanmar 2qm15 smoking in gear
thanks guys.

It wouldn't be growth. the boat only went in the water three days ago.

But the boat was out of the water for a couple years, if that matters.

I pulled the air filter and washed it prior to launch

CanadianNorth 07-05-2013 07:01 AM

Re: Yanmar 2qm15 smoking in gear
how would you check the pitch of the prop?

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