Blue Smoke above 1300 RPM Underload

[Lcliou]

Hi,

For the last 10 years after the last overhaul, often my A4 would emit lots of blue smoke in its exhaust when it is rev'd up above approx. 1300 RPM in gear. But the blue smoke would entirely stop as soon as I rev it down to a lower RPM.

My propeller is the three bladed, pitch-changing, Max prop, and the boat is Pearson Vanguard (32', approx. 12,000 lbs).

What is the cause for the blue smoke, and can it be corrected?

Thanks much.

Larry
Pearson Vanguard 32'
Hull #67, 1963

[joe_db]

My old engine did that. Old rings and valve guides I guess.

[Mo]

I agree with Joe. Are you using oil on a regular basis. If so, put some 15w40 in it and see if it helps. There are additives in it that make it less prone to burn off as lighter oils. Give it a try and see if it makes a difference for you...it has for many around here.

[thumbdoctor]

Oil fill and engine angle will contribute to windage hence oil burning / consumption

[jpian0923]

Blue smoke might be caused by "too rich" fuel mixture. Do you have an adjustable main jet?

A rich mixture can usually be leaned by adjusting the main jet (on an
early model carburetor), or by the installation of an adjustable main jet (in the case of late
model carburetors).

[thumbdoctor]

Blue smoke might be caused by "too rich" fuel mixture. Do you have an adjustable main jet?

A rich mixture can usually be leaned by adjusting the main jet (on an
early model carburetor), or by the installation of an adjustable main jet (in the case of late
model carburetors).

True, a rich mixture will cause smoke and burning eyes. Another test is to check what the exhaust outlet area looks like. Sooty or grimy, the latter isn't a good sign.

[joe_db]

oil = blue
too rich = black
coolant leak = white