Merc. 115 L4 - No Fuel To Cyl. 3 & 4

[FedUpWithBoatEngines]

Re: Merc. 115 L4 - No Fuel To Cyl. 3 & 4

Indeed it is very strange.

I can not really say for sure that there is less suction on 3 & 4 than on 1 & 2 but it just seemed lie the logical answer.

I spoke to my mechanic this morning and he seems to think that th engine has the wrong carbs on it and this is my problem.

In the Merc service manuel it says that only the top 2 carbs have an idle adjustment screw on them. Well all 4 of mine have them.

I have seen other pictures of carbs for these engines and they do not have idle mixture screws on the bottom 2 either.

 

[sschefer]

Re: Merc. 115 L4 - No Fuel To Cyl. 3 & 4

Indeed it is very strange.

I can not really say for sure that there is less suction on 3 & 4 than on 1 & 2 but it just seemed lie the logical answer.

I spoke to my mechanic this morning and he seems to think that th engine has the wrong carbs on it and this is my problem.

In the Merc service manuel it says that only the top 2 carbs have an idle adjustment screw on them. Well all 4 of mine have them.

I have seen other pictures of carbs for these engines and they do not have idle mixture screws on the bottom 2 either.

Ohhhhh. Somebody tried to convert this from a 2+2 to a full time 4. Looks like maybe the idea about getting another set of carbs on ebay would have been the right move.

 

[Faztbullet]

Re: Merc. 115 L4 - No Fuel To Cyl. 3 & 4

The seals look ok but there was that slight seepage from 3 to 4 I mentioned in one of my previous posts

This is normal as there are no seals on bearings...

 

[FedUpWithBoatEngines]

Re: Merc. 115 L4 - No Fuel To Cyl. 3 & 4

So I don't think I need a new set of carbs do I? These are the right carbs for this engine according to everything I've looked at.

 

[FedUpWithBoatEngines]

Re: Merc. 115 L4 - No Fuel To Cyl. 3 & 4

Also if anyone knows or has one of these engines. On carbs 3 & 4 is there a plug in the hole where the idle mixture screw is on 1 & 2 and the hole next to it is it open on 3 & 4??

 

[CharlieB]

Re: Merc. 115 L4 - No Fuel To Cyl. 3 & 4

Also if anyone knows or has one of these engines. On carbs 3 & 4 is there a plug in the hole where the idle mixture screw is on 1 & 2 and the hole next to it is it open on 3 & 4??

Correct.

3 & 4 idle screw ports is PLUGGED, as the carb body was not drilled for the pilot passage into the venturi. These carbs CANNOT be converted to an idle circuit.

So much for any other ideas, you already have it apart.

Is this motor 'new' to you or is this a recently developed problem?

What is the 'History' of work done and these carbs? Or do you know?

 

[FedUpWithBoatEngines]

Re: Merc. 115 L4 - No Fuel To Cyl. 3 & 4

Correct.

3 & 4 idle screw ports is PLUGGED, as the carb body was not drilled for the pilot passage into the venturi. These carbs CANNOT be converted to an idle circuit.

So much for any other ideas, you already have it apart.

Is this motor 'new' to you or is this a recently developed problem?

What is the 'History' of work done and these carbs? Or do you know?

My carb bodies are drilled. There is an idle mixture screw and a plug in the other hole. I am now almost 100% sure this is my problem.

I am going to move the plug to the idle mixture spot and leave the other hole open as I have seen in other carbs.

This motor is relatively new to me. I've owned it for about a month or so now. I am not sure what has been done to this thing. Although now that it's apart I believe it's been rebuilt. Not sure how to figure that out for sure though.

 

[CharlieB]

Re: Merc. 115 L4 - No Fuel To Cyl. 3 & 4

The hole that has the idle mixture screw on carbs 1 & 2 is the same hole that has the plug on 3 & 4.

3 & 4 did NOT receive the finish machining to complete the idle circuit, the actually seat for the needle nor the idle port thru the top of the carb into the throttle bore.

Leaving the plug out or in the wrong hole creates a massive air leak into the fuel passage between the main well and the port in the venturi, allowing the motor to suck AIR instead of fuel.

I would bet this has been the problem all along.

 

[FedUpWithBoatEngines]

Re: Merc. 115 L4 - No Fuel To Cyl. 3 & 4

I totally agree with you CharlieB. I can not believe that I overlooked this time and time again.

The powerhead is back together as of tonight. I will get it all back together tomorrow after work.

Also after inspecting the pistons closer with them out of the cylinders, this engine has been rebuilt and bored .015 over. It also looks as if the crank was replaced as well. Not such a bad thing I don't guess.

So another question. In the manual, it says there are NO bowl vent jets in any of the carbs. My #1 has a plug, #2 has an a actual jet, and now #'s 3 & 4 have nothing. So what should 1 & 2 really have??

Thanks again so much everyone has been a great help and I hope I can repay the favor one day.

 

[CharlieB]

Re: Merc. 115 L4 - No Fuel To Cyl. 3 & 4

#1 has a plug, #2 has an a actual jet, and now #'s 3 & 4 have nothing.

This is CORRECT for the port immediately LEFT of the idle screw, while the idle screw position have a needle screw on 1 & 2, then 3 & 4 have a small plug instead.

Sounds like the previous owner may have cleaned carbs, assembled them slightly incorrectly, gave up and sold it. Who knows, if he operated like this, it could have been the reason for the .015 pistons, the rebuilder missed the carb problem.


You may have gotten a great deal on what is usually a very reliable engine.

 

[FedUpWithBoatEngines]

Re: Merc. 115 L4 - No Fuel To Cyl. 3 & 4

Well engine is back together tonight.

She fired right up as usual, only this time when you rev the engine there IS FUEL to 3 & 4!!

On the water test coming tomorrow after we reset timing and link & synch. I think I am going to be in business.

I think I did okay on this engine. I originally paid $200.00 for it with FULL working guage set, controls, hydrolic steering too, a 16' SeaRay piece of shiz and an aluminum trailer in pretty decent shape. Engine originally had no spark on 2 cylinders. I got full electronics on ebay for $200.00 and solved my problem with lots of spare parts. (going to make another thread about a question I have with Red Stator) Spent another $300.00 on some new nuts, bolts, gaskets, motor mounts, water pump, fuel pump diaphrams, accelerator pump, spark plugs, 2-4-c, red sealer and check valves. And I know I bought some more stuff but cant think of it. But for under $900 I think I now have a good working engine and I know exactly what I have and how to take it apart lol..

Thanks!!!