E90TLCNB minor issue

[rejd]

I recently purchased a used boat with a 1982 90hp. I ran a bunch of checks on the engine and the compression was 100,104,100,106 which I beleive is within spec. Also ran a leak down test and all cylinders were around 10%. The one small issue I found was the two cylinders on the port side seemed to be running a little rich (plugs were a big darker and seemed to have a bit more oil on them then the other two). I know this motor has dual carbs but I'm not sure which carb feeds which cylinders. I would think that because those two were running rich that one of the carbs feeds those two. If that's the case I can assume that it's simply a carb adjustment needed to fix that issue? Other than that the motor seemed really strong. It fired up one the first turn of the key and ran smoothly.

Thanks in advance for any feedback.

 

[durban]

Re: E90TLCNB minor issue

both carbs feed port & starboard side the top carb the left\ hnd butterfly feeds the top piston starboard side & the bottom carb left butter fly feeds the bottom piston starboard side viewing from carbs to plugs k , port side the same

 

[rejd]

Re: E90TLCNB minor issue

Interesting. Why would the two pistons on the port side be running rich then?

 

[durban]

Re: E90TLCNB minor issue

fist of all make sure you have the correct heat range plugs in , secondly could be insufficient spark

 

[Faztbullet]

Re: E90TLCNB minor issue

Interesting. Why would the two pistons on the port side be running rich then?

A bad/stuck t-stat or stuck poppet will make that head run cooler and have incomplete combustion..

 

[Fleetwin]

Re: E90TLCNB minor issue

A bad/stuck t-stat or stuck poppet will make that head run cooler and have incomplete combustion..

Yes, you have to stats and two poppets. Also, the water deflectors, in one head may have moved. They are under the head covers. Easy to check.