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Saturday morning the boat started missing and carrying on a little, but not too bad, felt like too much oil in the mix.  By midday we decided to head back in and while heading to the dock it lost power and wouldn't rev over 3000rpm.

 

Started looking into it, cyl 1 had no compression and what I could see of the piston it looked pitted like there had been metal bouncing around in the cylinder.  Tore the power head down and the number one piston is shot, rings broken, etc.  The cylinder doesn't look too bad, I think I can hone it.  Cylinder 2 is .030 over, 1 and 3 are standard.  Cylinder 2 and 3 had about 95psi, which is lower than it should be, but about where it was when I first purchased the boat/motor.  I also noticed some rubber pieces (impeller) stuck in the hole in block where the water comes out to the water tell tale hose.  I haven't pulled the lower unit off yet to see if the impeller I put on about 2 years ago has broken, or if it's left over from the impeller I pulled out when I first got the boat. These motors are known for burning up the #1 piston due to fuel starvation, but it looks like it might have been lack of cooling water flow. 

 

From what I have read, not many places can bore these motors over (1983 merc 70hp) because the bores are blind holes.  So I am going to do some more digging and see what my options are. 

 

From what I can tell right now, my options are:

 

A rebuild for about 600 bucks in parts, maybe get it bored out if it's cost effective.  I don't need it to last another 20 years, so a quick rebuild with pistons/rings and honing the cylinders will be fine.

 

Buy a remanufactured powerhead (if one is available) for about 2000 bucks.

 

Find a used outboard, though I haven't had much luck looking for a decent 50-70hp.  I have been looking for a couple years knowing my motor probably wouldn't last much longer.

 

Buy a new outboard for about 7000 bucks.

 

I am going to be in the market for a different boat in a few years if all goes to plan, so I really don't want to repower with a new outboard, but I also am not in a place to get another boat right now.  Are there any other options I am not thinking of?  Has anyone else been through this scenario?  I would love to be back up and fishing so as not to miss the fall bite, summer has been rough and I have been looking forward to less scorching heat and better fishing.

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Personally, I would not consider anything but rebuilding it if you are able.  Too many rip offs out there in remanufactured power heads and not many people I would trust to rebuild one.  I guess I've been doing this stuff too long and have seem too much of what people get, when they think they are getting something else. 

Yes, it does have blind holes and most automotive machine shops are not set up to bore blind holes, and some that can do it want to charge stupid prices.  The only difference in boring heads is the standard boring head has straight cutting bits so they won't cut all the way to the bottom of the sleeve since the bottom is closed off with just a rod slot in it.  To bore an outboard block, they have to use offset cutters or have a boring head that does not have that big bolt head or nut on the bottom. 

Also, automotive shops know nothing about chamfering the edges of the ports unless they do and know how to do two stroke blocks.  If not chamfered, that sharp edge left from boring will hang and break the rings.

It's also a very common practice for repair shops or rebuilders to only bore one hole and stick an over size piston in just that one.  This is not a problem if they know what brand and/or weight match the pistons.  Most quality brands keep their piston weights the same so you can do that.  However, I have seen some with some ridiculous differences in weight and they wonder why their engine vibrated.

If the cylinder can be honed to no more than .002" over it's no problem, start getting more than that and you will probably start hearing a skit tick.  I have seen people take them as much as .004" over but as I mentioned, they will usually tick until they warm up.

Use a cylinder hone, and not on of those three finger glaze busters or ball hones if you are going to try honing it.  Before honing, use muriatic acid and cotton swabs on the long wood sticks to get the aluminum off the cylinder walls before honing.  Some times, once you get all the aluminum off, they actually look much better than you thought.

One other thought, make sure it's not a Nikasil sleeve.  I'm not that smart on black motors but I do know some of them run the nikasil sleeves, and that may only be in their racing engines.  I have seen people bore the plating off and just run standard pistons and rings because it's expensive to get one plated.

One other thing, if, after cleaning it up, it does not have deep scratches, the ball hone is your best bet for just doing a cleanup on it.  They will chamfer the ports to a degree also.

 

 

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I did some digging and found a local outboard shop that has been around for 40 years, that works with a machinist that does blind holes and is familiar with the old mercs.  So things are looking good for the machine work.

 

He said to order the pistons and send them along with the block.  Wiseco pistons run on the large size so the 30 over cylinder wont have to go to 40 over.  40 over is on the edge of a resleeve, so I'm happy to stay away from that.

 

 

 

 

 

 

 

 

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I would not use WiSCO's in a fishing motor.  The are a forged piston, expand more and require a couple thousandths more clearance, and when warming up, and require a much longer break in time.  For a fishing motor, it's actually better to run cast pistons.  The Wisco's are not larger, they just require a larger bore to allow for expansion.  They can also be fairly noise when cold because of that extra clearance.

I know you can get into the Ford vs Chevy type debate, but most all the most knowledgeable race engine builders around almost all recommend cast pistons for non high performance

builds.

Don't get too happy yet.  Check with the machine shop and see if they will bore a cylinder only .010".  Most won't because of the extra setup time and if there is any abnormal wear, .010" won't clear it, so they just go .020" intervals. 

Mic the .030" cylinder or have the machine shop check it and see if it needs bored.  Unless that's the one that blew, it may be good and you can just take the other two to .030"

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No help here, but I’ve been bouncing back and forth from a better used boat, to a lesser new boat because of this main fear. Curious to see what happens 

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I feel a lot of what type, how old, how new etc. depends on the financial situation and how much you know about boat and the confidence of being able to do a lot of the maintenance yourself.  If you are confident with your mechanical abilities, you can own older boats and motors and be happy.  If you don't know a boxed end from an opened end, then those older boats/motors can be the most expensive things you can own.  Of course, not everybody can afford to spend thousands of dollars on a new boat and have to make do with what they can afford.

I got married in 1969, I had bought two new boats prior to getting married.  Since getting married, I have probably owned well over 50 (buying, fixing and selling them), but I have never owned a new boat since.   

I have no problem buying any type of boat and in any condition.  Matter of fact, usually only bought one that had a bad motor or needed a transom, or floor replaced or some other major work, because those I would buy for pennies on the dollar.  There's nothing about one I can't fix so buying a nice looking boat with major problems, repairing and selling it was a good source of income for me.  Like my 1999 Javelin R20 DC, it was three years old and easily valued at $17,000.  I bought it at an auction in AZ for $4,500 because major parts of the motor were in the storage boxes.  It cost me $700 to get it shipped from Arizona to GA and $1,200 to repair the motor, so for $6,400 I had a $17,000 dollar boat and still using it with no other major problems. How many people can buy a boat, use it for 17 years and it still be worth what they paid for it.

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Ok, so I got my WSM cast pistons and rings in the mail, all .030 over.   Gasket kit, bearing kit, rod bolt kit, and carb kit are in the mail.  Cylinder 2 is already 30 over, skirt to cylinder wall clearance is tight to the spec, so a quick surface refinish wont do any harm.  Ring gap is also still within spec on number two.  He should have up to .001 to work with to hone before the ring gap opens above spec.  But realistically, I am sure it will be fine, I don't really run the motor that hard.  Heck, Mercury recommends trashing the block if the cylinder needs more than .015 to re bore, which is silly because there are oversize pistons to .040 available.  I am dropping the block and a piston at the shop tomorrow.  Guy says 3 or 4 days, 38 dollars a hole.  Maybe he will only charge me for two since number 2 is already bored, just needs a quick hone.

 

I will start to clean up the covers and caps and small parts while waiting on the block.  Lots of bolts to keep track of at this point!

 

I finally took the lower unit off tonight and the impeller that I put on a couple years ago is in fine shape.  I will put a new one in anyway, but what this tells me is that those bits of rubber I found in the cooling passageways of the block during initial tear down, have been rolling around in the block since at least as long as I have had the boat.

 

I plan on installing a temp sender in the cylinder head plate, and a gauge on the dash, so I can keep an eye on engine temp in the future.  A tear down was bound to happen, those rubber bits just happened to finally find a place to lodge and she overheated.

 

 

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Very reasonable price, some of the auto shops around me that will bore one want over $100 a hole, so if I had to do more than one hole, it's cheaper to ship it out to be done.

Be sure to see if they chamfer the ports or if they expect you to do that.

It sounds like you know what you are doing but be sure to scrub the those sleeves good to make sure all the honing grit is out.  Also, on two stroke motors you have to be sure the flush the ports good, especially the exhaust port, the honing grit in the port passages and can be pulled back into the cylinder.  Not many places run the block back through the washer after boring/honing.

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11 minutes ago, Way2slow said:

Very reasonable price, some of the auto shops around me that will bore one want over $100 a hole, so if I had to do more than one hole, it's cheaper to ship it out to be done.

Be sure to see if they chamfer the ports or if they expect you to do that.

It sounds like you know what you are doing but be sure to scrub the those sleeves good to make sure all the honing grit is out.  Also, on two stroke motors you have to be sure the flush the ports good, especially the exhaust port, the honing grit in the port passages and can be pulled back into the cylinder.  Not many places run the block back through the washer after boring/honing.

 

Thanks for the tips!  If they don't chamfer the ports, how much massaging are we talking here?  just breaking the sharp edge, or more?

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Since you are probably not experienced enough with a die grinder that's all I would recommend doing.  If you get the ports out of shape, it can make the rings beat against the locator pins and make them loosen and back out in a rather short time.  I know a lot of the Mercury guys just hone with the grape ball hones and say that chamfers them good enough.  I've never done that, so not sure what it would do to the cross hatch the machine shop is charging you to put in them. 

I get very technical with mine and do a .050 chamfer and then hand massage them with 220 grit but I'm usually running a pretty wide exhaust ports so  want to be sure that rings does not pop out far enough to hang the edge.

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I'm just curios so gotta ask.  For the cylinder that blew, did it clean up pretty good and you are sure a .030" over bore is going to fix it?  You said you have already gotten the pistons and taking it to the machine shop so I guess it looked pretty good.

I know it's a little late in the ball game, but you did inspect the crankcase and make sure there was no damage there I hope.  If you are having a really bad day, there is very little clearance between the crank/rods and the crankcase so if a piston comes apart, pieces can get into spaces they don't fit and that spinning crankshaft makes room for them, sometimes to the point of putting big holes in the crankcase.

It can make you feel real good when you pull the cowling off and see the rods and crank looking at you from outside the engine.

 

One other thing, Loctite 518 gel seal is good for putting the case halves back together.  A lot of these manufactures make it sound like you have to have their brand, when it's probably 518 anyway.  I also put a drop of 242/243 on the rod bolts. 

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8 hours ago, Way2slow said:

I'm just curios so gotta ask.  For the cylinder that blew, did it clean up pretty good and you are sure a .030" over bore is going to fix it?  You said you have already gotten the pistons and taking it to the machine shop so I guess it looked pretty good.

I know it's a little late in the ball game, but you did inspect the crankcase and make sure there was no damage there I hope.  If you are having a really bad day, there is very little clearance between the crank/rods and the crankcase so if a piston comes apart, pieces can get into spaces they don't fit and that spinning crankshaft makes room for them, sometimes to the point of putting big holes in the crankcase.

It can make you feel real good when you pull the cowling off and see the rods and crank looking at you from outside the engine.

 

One other thing, Loctite 518 gel seal is good for putting the case halves back together.  A lot of these manufactures make it sound like you have to have their brand, when it's probably 518 anyway.  I also put a drop of 242/243 on the rod bolts. 

Yes, everything looked good on the bottom end, I didn't find any metal below the pistons.  All reed guide gaps are within spec, reeds fit tight etc.  No evidence of anything banging around down there.  Just on top of the piston.

 

Yes, 518 is the product I am going to use.

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