Puffs of smoke from intake

I have a 1990 Johnson 175 VRO and while idling, about every other or maybe every third rotation I would get a puff of white smoke from the bottom carb and the engine skipped. It was less frequent as the engine fever higher and at about 1/2 throttle it went away. I suspected reed valves but got into those today and they look good. Carbs were recently cleaned but this didn't start till about a month after that. I am doing a full rebuild but would like to know what's causing this.

It is supposed to say "revved" higher, not "fever."

The only reason it would spit back out the carb is a reed issue you need to look close at the reeds and replace the defective one/s.

Alright, I will take another look. I am going to take them off this week sometime and check the gaskets. I noticed a lot of oil settling at the bottom of the intake and the bottom cylinders. Maybe the gaskets went bad. I think the gasket went bad between the intake and the crankcase cause I had a oil leak from somewhere and it looks like it may have been coming from there.

The only reason it would spit back out the carb is a reed issue you need to look close at the reeds and replace the defective one/s.

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and while idling, about every other or maybe every third rotation I would get a puff of white smoke from the bottom carb and the engine skipped.

Click to expand...

A bad reed would make it spit ALL the time not intermittently. The puff is from a lean crankcase mixture or timing issue. This model is prone for ignition problems due to the T pack and flywheel hub magnet, there is a TSB on spark wires as the burn out around spring in boots. Leaking intake gasket may cause this and where are you seeing oil as its mixed in VRO/OMS if still equipped???

I was thinking that the oil was odd because it should be mixed. Yes VRO is still equipped. I have all kinds of oil. Some at bottom of powerhead on outside and inside. I have oil leaking through misection but I think that may be coming from same place. I have also seen it come from lower unit, but again I think it is all coming from the same place. I suspect that, yes the VRO is mixing it but then after leaking the gas evaporates and leaves the oil behind. I have definitely smelled fuel before. This was a main reason for the rebuild. I think all the seals and gaskets are worn out.

Try replaceing cap on oil tank first as the vent in top goes bad..this will let tank pressurize and push oil thru VRO usually into the carbs.

Is it possible you have a oil recirc hose disconnected?

Ok. I'll give that a try too.

Have a theory, let me know if I am totally off. So, today I disassembled the intake and reed boxes. The boxes and reeds seem to be in pretty good shape except they seem to be saturated with oil. Could it be possible that there is so much oil on them that the sheen of oil is keeping them open, therefore allowing combustion to escape through them?

All in all, they looked good, seemed like they had a pretty good seal. The gaskets were in great condition other than being covered in oil all the way through (could also be the cause, I suppose).

Are all the leafs flat up against the boxes the manual gives you the spec on how far the leaves can be open. The oil theory in my opinion would be the oil would make the leaves seal quicker. Have you done a compression test? Possibly the VRO is putting out too much oil. To check the ratio the most accurate is to top the fuel tank off and the oil reservor. put a mark on the oil level in the reservor. run the tank close to dry the more fuel the more accurate. find out how much fuel in ozs it takes to top the tank off then measure the oil back up to the line in ozs. Divide oil into fuel should be close to 50:1. If your running at higher altitudes with low altitude jets the crankcase will load up with oil. Are you lugging the motor (over propped) or water soaked double bottom? Is the motor reaching proper WOT rpms? There is a explanation start with a proper diagnostic. In order compression, spark gap test, cylinder drop test, check sync, are the carbs opening exactly the same time, is the hull clean and the double bottom dry, what is the WOT rpms? There is no combustion in the crankcase unless the rings are bad. What happens is when the piston is going down is precharges the chamber with fuel oil mix and when the pistontop reaches the intake port the fuel precharge is forced into the cylinder pushing the exhaust gas out. then when the piston starts going up it creates a vacuum pulling fuel mix into the crankcase. The reeds only allow fuel mix to flow in one direction and the mix lubes the internals at the same time. Normally coughing out the carb or spitting fuel is a reed that is not closing properly or missing. You can do a compression test with the reeds off get back with the numbers.

The only way oil could be here is after the engine has set for a few days and the fuel evaporated leaving oil residue. This much oil as you post mean the recirculating system is not up to par.Also when starting it should smoke real bad. I reread post an you stated your doing a full rebuild..is this the carbs or the engine??? If engine is it the carb on bad cylinder???

Reeds coated in oil are not the problem !!-----And as stated the combustion process is nowhere near the reeds.