1987 evinrude 140 looper power head rebuild

[Joker86mk]

hey guys, I had purchased a doral bowrider with a non cranking engine, i disassembled the engine to find that one piston had hit the head , piston was cracked and the wrist pinhad engraved the cylinder walls. seems as if the rings have let go and got jammed cracking the piston not sure. I sent the bare block to get sleeved and rebored jsut got it back about to reassemble. I am wondering is there anything i need to look out for while reassembling any tips. any other parts i should replace before running this engine. currently i am replacing all pistons and bearings in the powerhead thermostates and lower end fuids. also boysen reeds
also can i run the engine with muffs how long and what rpm
Thanks

 

[Faztbullet]

Re: 1987 evinrude 140 looper power head rebuild

If this is the 90? looper version make sure the bridgeport on the exhaust is modified as the aftermarket pistons are not drilled to cool it.......

 

[Joker86mk]

Re: 1987 evinrude 140 looper power head rebuild

Sorry I'm not to familar with out boards what is the bridge port , the pistons are vertex coated pistons

 

[Solittle]

Re: 1987 evinrude 140 looper power head rebuild

So at this point you don't know what caused the rings to let go??? If you don't determine why there is a chance they will let go after you finish the rebuild. At a minimum I would rebuild the carbs. Also the water pump, t-stats and deflectors in the power-head. And get the OMC shop manual for the break-in process.

 

[Joker86mk]

Re: 1987 evinrude 140 looper power head rebuild

heres a pic, it is only one pistone the other three are like new. i am replacing the impeller, reeds, thermostate and probably get rid of the vro or premix till im sure it is working. i do have the service manual aswell. the engine didnt look as if it was overheated im assuming the ring might have been stuck or something. not sure

what is the deflector

 

[Haffiman]

Re: 1987 evinrude 140 looper power head rebuild

The way the piston looks what does the head look like?
Most likely NOT to be reused!!

 

[Joker86mk]

Re: 1987 evinrude 140 looper power head rebuild

the head had some rough spot of metal melted to it, but i sent it out when i sent the block out and he was able to clean it up and smooth it out so it should be good now. the cyclinder of the piston was a disaster the wrist pin almost went through the sleeve walls. piston was broken where the wrist pin was.

 

[Haffiman]

Re: 1987 evinrude 140 looper power head rebuild

The only way to 'clean out' would be to remove material, which again will be loss of compression!
It might work if he does both chambers and then machine down the head. If so you might need washers under the head screw to compensate a 'thinner' head depending on how much has been removed.

 

[coolguy147]

Re: 1987 evinrude 140 looper power head rebuild

that motors defiantly needs a decarb treatment...

 

[Joker86mk]

Re: 1987 evinrude 140 looper power head rebuild

finalllly done full rebuild changed all pistons, bearings , everthing pretty much ... now i need to start it , how high can i run it on the muffs?.. also anyone running boyson reeds with out changing the idle jet

 

[dazk14]

Re: 1987 evinrude 140 looper power head rebuild

Congrats! How did you align the rods/caps? Fyi - Those are idle air bleed orifices. A smaller # will richen up the mixture. How many sizes does Boyesen suggest going down? Did you test the function of the recirculation valves. They can cause idle issues.

Oh, about 1500 max. You can give a few blips off idle that might run momentarily (by momentum) up to 2500.

Edit: I just reread your post..I thought you were dunking it in a tank. With muffs about 1000max continuous with quality muffs and good volume. Blips off idle to 2k.

 

[Joker86mk]

Re: 1987 evinrude 140 looper power head rebuild

I used a pick to align them like it says in the service manual . Boyesen suggests. If it has idle air jets to down size by 5. If it has low speed fuel jets to increase by 2 sizes ... Also it main be fine and won't need to change sizes. I tested all the one way valves and cleaned all passages and replaces all worn hoses

 

[dazk14]

Re: 1987 evinrude 140 looper power head rebuild

Sounds like you've done a 1st rate job. You may want to start a new thread asking for specific Boyesen V-4 Looper experiences.

I'm sure you're already aware you don't get too many bites at the apple if it is lean sneezing.

 

[Joker86mk]

Re: 1987 evinrude 140 looper power head rebuild

jusat started it, but it idles at 1500 -2200 rpm , might be from the reeds not sure

 

[dazk14]

Re: 1987 evinrude 140 looper power head rebuild

That much won't be due to reeds. Sounds more like link and sync.. There is a process laid out specifically in the service manual and an order that needs to be followed.

You may have a bank (or both) throttle plates that aren't fully closed. The ideal time to set these up is when the carb bodies are off, but it's still easily serviced after the fact.

The roller cam follower should not be touching the cam at idle.



Glad to hear you've got it running!