Mercury 40hp lower vrank seal replacement

[crotonpond]

Do I need to split the cases to replace a lower crank seal on a mid 90s Mercury 40hp 4 cylinder?

 

[racerone]

Serial # is ?----In the past I have pulled the bearing housing off without splitting the block.----Replaced lower ball bearing too.-----What is your motor doing / not doing ?

 

[crotonpond]

0G107604

Wont start. Has spark, compression, rebuilt fuel pump, rebuilt carbs. Im getting fuel to the bowls, but it wont fire. It will fire if I put premix directly into the carb throats...Has to be a bad crank seal.

 

[racerone]

NO NOT AT ALL.----------Your motor has 4 separate crankcases.-----The motor would start and run on the other 3 cylinders !!!-----Is the choke / enricher working.-----Pushing the key in while cranking it over ?--

 

[crotonpond]

Really..so two inner seals and two outter seals? I was pushing the key in while starting, but not sure if the enrichner is working..do you test it under cranking amps?

 

[racerone]

Fact for you.-----There are 4 separate crankcases and therefor 5 sealing elements .------There is some testing / trouble shooting to do on your part.

 

[jimmbo]

Really..so two inner seals and two outter seals?

You really are not familiar with the inline mercs. There are positive seals on the crank at the top and bottom of the crank. Between cylinder 1 and 2, and also 3 and 4, there are what are called Labyrinth Seals. These are basically groves in the crank shaft bearings that fill with oil, and effectively isolate the two crankcases from each other. Between cylinders 2 and 3 there is enough in the way of bearings and oil to do the same

 

[crotonpond]

Thank you. That helps clarify that my baseline urge to blame a crankseal is foolish. I have limited experience with these motors, but enjoy learning and problem solving. I supose a service manual is my next plan of action.

 

[jimmbo]

The upper seal is prone to wear and eventual leakage. Sometimes running a 24:1 gasil mix will help the seal perform better for a while. On the Merc engines the seals are usually not too difficult to replace as they are in a Bearing Housing that can be removed with out splitting the crankcase.

As for the Service Manual. Get the proper Factory Manual. Merc Manuals are a little weak when it comes to explaining the operational theory of the motor(I assume these books were written for actual Techs) but they do explain the disassemble/assemble of the engine and things like specific Link and Sync procedures, wiring diagrams, etc

 

[crotonpond]

Does anyone have an electrical schematic for this motor? I have been able to get the motor to run. When cold, it will run for a few minutes, but then it will quickly die. I hooked my test light up to my plug leads and I have no spark. It appears to be intermittent. I need to start testing the electrical system, but I do not have a service manual. Thanks in advance!