Help No Compression

[ray914]

Here I am again, I ran my 135 black max today with some quickkleen from the merc guy. It seem to have ran fine idled better and smoother. BUT when I got home and did a compression test my bottom cylinder read 0 psi. Is it possible for it to idle and run decent without the one cylinder? How hard is it to replace that one piston/rings? Am I wasting my time???????

 

[achris]

Re: Help No Compression

I would find it surprising if you didn't notice one dead lung. Did you recheck the compression to make sure it wasn't just a case of the gauge not reading? And check on another cylinder too, to verify the gauge is still working.

Chris.......

 

[Moody Blue]

Re: Help No Compression

I had a 4 cyl that ran on 3. Idle was rough but higher RPM's were smooth. It just lacked full power.

Re-do the compression check or stick your thumb over the plug hole and spin it over. You'll know if it is "0" or not.

How hard to repair? Simple question, complicated answer.

Depends on what is wrong, how handy you are with a wrench, how much time you have and do you have a proper manual.

 

[sschefer]

Re: Help No Compression

Here I am again, I ran my 135 black max today with some quickkleen from the merc guy. It seem to have ran fine idled better and smoother. BUT when I got home and did a compression test my bottom cylinder read 0 psi. Is it possible for it to idle and run decent without the one cylinder? How hard is it to replace that one piston/rings? Am I wasting my time???????

One hole down is usually the point where most shops will recommend a powerhead replacement. I will too. It's a lot of work and money to rebuild a powerhead on your own and you don't know what else might be wrong with it.

If it was mine, I'd order a new powerhead and put this one away until next winter. When the seasons over have a go at it. Or, part it out on Ebay to help pay for the new powerhead. If you work it, you can come pretty close to even.

 

[ray914]

Re: Help No Compression

Hey guys got home this evening and this is what I found. The story behind this is it hadn't run in 4.5 years. I put a waterpump,thermostats, starter solenoid and changed the lower unit oil plus cleaned out the carbs. It started fine I changed my boat power from a 90hp evinrude to a 135 mercury black max and all the controls. It had a weak cylinder and I trimmed it all the way up and soak the cylinders with seafoam for about a day. then turned it over numerous times put the plugs back in it and fill the gas tank fresh fuel 7 gallons, and put in 8 ounces of mercury quickclean (recommended by a mercury guy) went to the lake ran it about 30 minutes high speed and idle, various speeds and numerous start ups. Got home did a compression check #5 cylinder 0 psi. It was 60 psi before running it. The rest 110 psi. Am I wasting my time with this motor. Can I hone the cylinder (it's not bad at all) put a piston and rings in it and cross my fingers.....I'm sorry for the long reply and take a look at the picture. The head on that cylinder looks like the piston. Ring's broke and beat the heck out of it?

 

[saumon]

Re: Help No Compression

A honing and rings WON'T be enough. You'll need to rebore that hole and put a new piston.

Turn the flywheel until that piston is at the bottom and check the condition of the cylinder wall. If you can feel the scratches with your fingernail, you'll have to rebore.

 

[IronOutlaw]

Re: Help No Compression

If he bOres the cylinder and only changes one piston won't that throwoff the balance of the rotating assembly.

 

[saumon]

Re: Help No Compression

No. Oversized pistons are larger but weight exactly the same as regular ones. You can even match 3 rings models with newer 2 rings ones.

 

[ray914]

Re: Help No Compression

Stupid question can it be bored without taking the power head off? I understand replacing the piston/rings isn't that difficult. My understanding is to take off carbs,reed valves and reed valve plate to get to the crank bust loose the rod nuts and slide it out the head side of the cylinder? Am I being told wrong?

 

[saumon]

Re: Help No Compression

Stupid question can it be bored without taking the power head off? I understand replacing the piston/rings isn't that difficult. My understanding is to take off carbs,reed valves and reed valve plate to get to the crank bust loose the rod nuts and slide it out the head side of the cylinder? Am I being told wrong?

No. You'll have to completely strip it to the bare block for a rebore. It has to be put on a bench for milling. Even for a simple honing, that can be done with a handheld drill, you have to completetlly undress it cause you need, afterward, to wash it thoroughly in warm soapy water. If you don't, all the grit will toast the crankshaft bearings in no time.

And yes, you can slide a piston out that way, but it's pretty useless.

 

[sschefer]

Re: Help No Compression

No. Oversized pistons are larger but weight exactly the same as regular ones. You can even match 3 rings models with newer 2 rings ones.

This is correct. There is a slight amount of difference in weight but not enough to make it a problem. When you consider that the rods can be off by as much as 20 grams without causing a problem in a stock motor the piston weight won't matter. Merc allows up to 3 pistons to be oversized before doing all 6.

 

[JaseBosto]

Re: Help No Compression

seems kinda stupid to me, to do all the work of stripping it down only to bore one cylinder. If it was me, I would just re-do the whole thing while your there. When its all said and done with, you would have a fresh motor that is done right.

 

[sschefer]

Re: Help No Compression

seems kinda stupid to me, to do all the work of stripping it down only to bore one cylinder. If it was me, I would just re-do the whole thing while your there. When its all said and done with, you would have a fresh motor that is done right.

I agree to a point. In my local area it's 80.00 a hole to bore and hone. There's only one shop that can bore a blind hole within 100mi and this time of year boring all six is a month out wait.

Pistons can run from 50.00-130.00 each, rod bearings 25.00 each set, etc. You can wrap 1500.00- 2000.00 into a engine really quick and if you don't have that kind of cash then a single cylinder is the way to go and is perfectly acceptable. It's even done quite often in the performance world.

 

[bryanwess2000]

Re: Help No Compression

I'd just keep an eye out for a merc v6 with a busted lower unit and drop
the power head on your 135 mid/lower a 2.0, 2.4, 2.5 should bolt up. Rebuilds
can get expensive quick if done right. I'll end up spending >$300 on my 3cyl
90hp and thats just pistons, needle bearings and gaskets. Thats with me
resizing my bores with ~$500 of equipment I bought.

 

[sschefer]

Re: Help No Compression

I'd just keep an eye out for a merc v6 with a busted lower unit and drop
the power head on your 135 mid/lower a 2.0, 2.4, 2.5 should bolt up. Rebuilds
can get expensive quick if done right. I'll end up spending >$300 on my 3cyl
90hp and thats just pistons, needle bearings and gaskets. Thats with me
resizing my bores with ~$500 of equipment I bought.

Yep... Been meaning to ask you.. Which mobile hone did you get.. I had a Sunnen that I loaned to my brother who seems to have lost it.. I can't remember the model number on it, I bought it 20 years ago. I was looking over at Goodson.

 

[saumon]

Re: Help No Compression

I agree to a point. In my local area it's 80.00 a hole to bore and hone. There's only one shop that can bore a blind hole within 100mi and this time of year boring all six is a month out wait.

Thoses shop are rare. I'm doing business with one 300 miles away, located in Peterborough, Ontario, but they know their stuff. They charge around 60$/hole.

http://www.marinemedics.com/services.php

They also have quite an impressive inventory: ?We have an inventory of over 800 core blocks in stock at any given time along with a large inventory of new and used parts such as rods, crankshafts, and pistons.?

 

[ray914]

Re: Help No Compression

Well I tore it down I've got it loose but can't for the life of me get the front of the crankcase off????? It looks as if it needs to go straight up about an inch and then off. Do I have to loosen the whole power head from the mid unit and then it'll come off? The top of the crank case will move about 3/16 of an inch but the bottom will not move at all . Yes I have the two large bolts at the bottom out. I tried the power head bolts at the back of the motor 4 total and tried to separate the power head no luck. I guess my dumb butt would benefit tremendously with a shop manual. Is there anywhere I can get a picture of a broke down power head of a 135 black max? Thank you everyone for your input.

 

[saumon]

Re: Help No Compression

Well I tore it down I've got it loose but can't for the life of me get the front of the crankcase off????? It looks as if it needs to go straight up about an inch and then off. Do I have to loosen the whole power head from the mid unit and then it'll come off? The top of the crank case will move about 3/16 of an inch but the bottom will not move at all . Yes I have the two large bolts at the bottom out. I tried the power head bolts at the back of the motor 4 total and tried to separate the power head no luck. I guess my dumb butt would benefit tremendously with a shop manual. Is there anywhere I can get a picture of a broke down power head of a 135 black max? Thank you everyone for your input.

Yes, you need to remove the powerhead to split the crankcase.

And we need at least the year or the serial number to point to a diagram.

 

[sschefer]

Re: Help No Compression

Yes, you need to remove the powerhead to split the crankcase.

And we need at least the year or the serial number to point to a diagram.

The lower bearing cap is what's hanging you up. Go to www.crowleymarine.com and look at their parts list. You must remove the powerhead from the mid section to get those last two bolts out.

 

[sschefer]

Re: Help No Compression

Thoses shop are rare. I'm doing business with one 300 miles away, located in Peterborough, Ontario, but they know their stuff. They charge around 60$/hole.

http://www.marinemedics.com/services.php

They also have quite an impressive inventory: ?We have an inventory of over 800 core blocks in stock at any given time along with a large inventory of new and used parts such as rods, crankshafts, and pistons.?

Yep, I'm in California, the land of high overhead and excessive taxes. Shop time is 95.00 an hour. Just had a front half cut and it cost me 210.00. Makes me wish I still had that old Bridgeport Mill I decided not to fix.