Merc V-150 Rebuild

[Outrage 19]

And so it begins. I got the engine torn down this weekend; it’s been so long since I had one of these things apart I forgot how clean they are inside compared to 4 stroke automobile engines. AndyL thanks for the reply to my Flywheel post I got it off using the two bolts but I’d still like to know if it’s ok or if I was just lucky. <br /><br />OK list of damages.<br />1 chewed up piston.<br />1 cylinder that has heavy aluminum deposits, the one the chewed piston came out of.<br />3 sets of seized piston rings.<br />2 slightly scored cylinder walls; so slight you can only see the scores not feel them.<br />2 bent reed valves; lifted up from there seats about 1/16”.<br /><br />Questions<br />1 The diminutions of the piston I bought off of ebay are identical to the other pistons in the engine except for the, distance where the wrist pin goes through the connecting rod which is 7/16” smaller on the ebay piston. A millwright I know has offered to mill out the difference is there anything I’m not aware of that would make this not a good idea?<br /><br />2 What is the best way to clean the aluminum off of the cylinder wall, honing?<br /><br />3 Can I just free the seized rings or should I replace these pistons also?<br /><br />4 Can I just flip the bent reeds over and reuse them?<br /><br />5 The worst of the bent reed valves is on the cylinder with the chewed up piston. Is this most likely what caused the cylinder to lean out and run hot burning up the piston? As someone on this forum says “It doesn’t do any good to fix the symptom if you don’t fix the cause”<br /><br />

 

[kingsbiship]

Re: Merc V-150 Rebuild

you will never be successful or happy with the path you are taking! Cutting the piston will weaken it's structural integrity. In you're case<br />theres no short cuts. (Known from experience)

 

[Outrage 19]

Re: Merc V-150 Rebuild

Bump

 

[Dhadley]

Re: Merc V-150 Rebuild

That light at the end of this tunnel just may be a train.........<br /><br />What motor do you have? What piston did you buy? What did it fit? I cant think of a V6 Merc piston that has a wrist pin almost 1/2" smaller than another. What brand piston is it? What rings are you going to use? Never mind what the cylinders look like - what do they measure?<br /><br />If you make the wrist pin hole that much bigger what are you going to use for retaining clips? What interference are you going to use for the pin fit?<br /><br />Have you got a manual?

 

[Outrage 19]

Re: Merc V-150 Rebuild

Sorry Dhadley I forgot to add the particulars. This is a 1987 Mercury 150 hp V6 SN: 0B156087. The piston was bought off of ebay and was advertised as for all 2.0 liter V6 Mercury’s 135, 150, 175 hp.<br /><br />With a micrometer my machinist buddy checked inside diameter, outside diameter, height, location and dimensions of the various holes and cut outs, location of the ring groves, and diameter of the wrist pin, both pistons use tapered rings. The only difference he found was the distance inside the piston where the wrist pin goes through the connecting rod. If I have him do this I will give him the opposite piston for a weight comparison.<br /><br />The big question I have is, are the reed valves to blame for the piston burning up in the first place?

 

[Outrage 19]

Re: Merc V-150 Rebuild

Sorry again I was not finished answering all of Dhadley’s questions. Yes I have a Clymer manual for this outboard.

 

[dkondelik]

Re: Merc V-150 Rebuild

the only question? hmmmmmm. OK<br /><br />REPLACE THE REEDS.<br />turn em over and they'er sure to die an early death,.. and take a/some piston(s) with 'em.<br /><br />Yup! bad reeds sure are likelysource of burnt piston.<br /><br />Good Luck

 

[Outrage 19]

Re: Merc V-150 Rebuild

Again I must apologize I was too hasty in reading you reply Big D. It’s not the wrist pin hole that is too small it’s the distance inside the piston where the wrist pin goes through the connecting rod.

 

[Outrage 19]

Re: Merc V-150 Rebuild

Thanks Klondike7 should I replace all of the reeds or can I replace just the bent ones?

 

[Dhadley]

Re: Merc V-150 Rebuild

What you have is a piston for a top guided rod. I suppose you could open up the inside distance for the bottom guided rod and rebalance all the other pistons to that one. Sure seems like a lot of work. <br /><br />Besides, once you measure the cylinders with a dial bore gauge Ill bet you will need to oversize the cylinders anyway. <br /><br />The reeds are a no-brainer. A set of Boyesens are very reasonable. Its almost a shame to not install them even if the reeds were OK.<br /><br />Sounds like you are familiar with automotive type motors. Just remember not to get crazy cutting the deck and heads. This is a Merc -- not a Chevy.<br /><br />Good luck!

 

[dkondelik]

Re: Merc V-150 Rebuild

i'd listen to Dhadley,<br /><br />& i'd listen to him again.<br />replace 'em all with the Boyesen's.<br /><br />let us know how it's going, what you run into and how it turns out.<br /><br />Enquiring Minds want to know.<br /><br />Good Luck

 

[Outrage 19]

Re: Merc V-150 Rebuild

Thanks for the replies Dhadley and Klondike7. Actually I’m familiar with both I worked at an Evenrude dealer in my early 20’s, from 83 to 84, and I’ve been working on cars since I was 13.<br /><br />I see Mercury wants $288 for a full set of reeds, and Boyesens are $173. I’ll go Boyesen.<br /><br />I don’t have a dial bore gauge but I do have a set of snap gauges. What’s the best way to clean the aluminum deposits off of the cylinder wall so I can measure the bore?<br /><br />As far as doing anything fancy with this engine I’m not looking for fast I’m looking for reliable. It’s going on a 19’ Boston Whaler Outrage. I’ve already been warned about the effects of cutting heads and over heating on this type of engine. Unfortunately like most people out there I don’t have a fortune I can spend on this project.<br /><br />Once again thanks for the great advise. Even thou I use to do this for a living it was a long time ago.

 

[Outrage 19]

Re: Merc V-150 Rebuild

I checked the bore on the 5 cylinders without aluminum deposits. They were all within .002” each way. The manual I’m using says finished honing should be 3.125”. My readings were all around 3.120”. Is 3.125” the maximum bore for a standard piston but they come out of the factory with smaller bores?

 

[Dhadley]

Re: Merc V-150 Rebuild

It should indeed be 3.125". If you are sure you are there then no boring is necessary. The cylinder that scored the piston will most likely have to be bored. Most of the time the cylinder distorts from the heat created during the scoring. Make sure you measure it at the top and bottom to compare. Its hard to measure in the middle of the travel but try to get a reading there too.<br /><br />Sounds like you are good to go. <br /><br />Good luck!

 

[Outrage 19]

Re: Merc V-150 Rebuild

Thanks Dhadley as always your advice is greatly appreciated. I read in the manual do not use any automotive solvents to unstick the seized rings. Does anyone have any suggestions as to what is a good solvent? I have easy access to mineral spirits and denatured alcohol, is ether one of these expectable?

 

[dkondelik]

Re: Merc V-150 Rebuild

i hope that mineral spirits are ok 'cause I use the "heck out of 'em".<br />mineral spirits, an old tooth brush and ocasionally an ultrsonic tank (with mineral spirits) and those grungy ol' inside parts look like new. with patience, even the ring grooves clean up real nice.<br /> <br />on disassembled parts, spray-carb ceaner does a good job too but keep it away from rubber parts.<br /><br />never used alcohol so can't speak to that subject.

 

[Outrage 19]

Re: Merc V-150 Rebuild

Thanks klondike7, mineral spirits it is.

 

[Outrage 19]

Re: Merc V-150 Rebuild

I got the block cleaned up this weekend and honed the one bad cylinder out as much as I could. There are still some aluminum deposits left on the cylinder walls and some minor scoring. Finish dimensions are 3.122 X 3.125, as stated in a previous post the book says the maximum bore for a standard piston is 3.125. Is this good enough or do I have to get this cylinder bored to remove all of the aluminum?

 

[Outrage 19]

Re: Merc V-150 Rebuild

bump

 

[Outrage 19]

Re: Merc V-150 Rebuild

Ok no one wants to touch that one how about this. Can this head be cleaned up or does it need to be replaced?