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Mercruiser 120 specs 1964- 72 Gm

FishingTheFL

FishingTheFL
in This Old Boat

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lakebound88

lakebound88

Posted
Posted

Carbs adjusted at idle

Only adjust the idle screws. But that's not why you're smoking. You're burning oil and blow hy, that's why your breather on the valve cover has so much exhaust gas coming out of it. Compression means nothing I this case, especially with the knock. A true leak down test per cylinder should be done.

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Xxx

Xxx

Posted
Posted

Hey Lake if the motor is that far gone you can turn at screws till he is blue in the face and it will not help!! I strongly feel she has seen her better days. If she's puff the magic dragon out of the breather vent, defiantly not good, major blow by. I didn't know it's as bad as you say. He says it still back fires through the carb, the timing was way off, we are now in the ball park, a severely burned valve with act like that also. Just pull the the motor and have it rebuilt or purchase a good used one. I personally would rebuild the old one, then you know what you have. Write the rest of the season off and do it as the funds allow!! Been there done that. LOL!!

FishingTheFL

FishingTheFL

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Posted

Ever since I changed the plug, no smoke comes out the breather, some did when messing with the carb to lean and a ton of black suit come out.

I got the timing right now after Pap sent me some pics. Tuned the carb. I'm going to give a test to see what my results are. Even with the knock I can sell or rebuild. Not running at all, its scrap on a wheels. The knock is coming from where lake said.

As for funding, winter is coming. I may have one big job coming in, may not... I'm weighing my options still

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FishingTheFL

FishingTheFL

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Posted (edited)

So I took it out. Ran great for about 20 mins, I idle down and it pretty much dies I have a slow idle back to the dock but I think its just a plug. At a higher idle the knock seems to go away. Any idea why it would keep fouling plugs

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Plugs where not fouled... Give any gas and it dies out... Ugh

Edited by FishingTheFL
lakebound88

lakebound88

Posted
Posted

Just so you know, continuing to run it with the bad bearings, you are liable, hang on, you WILL blow the motor and seize it. You will either throw a rod out the pan or the side of the block then you will really be out money. Changing your plugs wouldn't stop the exhaust out the breather. Just a coincidence IMHO. You can play with all this other stuff all ya want. But, when a bearing is bad and the motors knocking, it means there is metal on metal or no lubrication to that particles point of a moving part. If you have spun a bearing, you are just destroying the motor even further, pumping that metal through every other bearing in the motor, slowly building an etch a sketch picture on all bearings until it goes silent.

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FishingTheFL

FishingTheFL

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Thanks for the info. I don't plan on using it now that you put it that way. I can put a magnet in the pan for metal correct? I'm just amazed I got something to work lol. What you say about my boat motor gets me worried about my Stump grinder. Lots smoke out its breather and that thing takes so much abuse...

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lakebound88

lakebound88

Posted
Posted

For magnetic metals yes but bearings are not metalic, they are considered tin, or babbitt I beleive. You won't be able to extract these, your filter does this, however extracting it still will not fix your problem. I will post photos of a spun bearing for you.

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lakebound88

lakebound88

Posted
Posted

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These are just examples. These can't be seen without removing the pan and removing the rod caps or main caps.

How old is your machine? If she's a runner I wouldn't over think it. Most engines have crankcase pressure of some sort, but there is excessive amounts that can raise concern. Don't over this this on your other machine. We're talking boats here.

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rolmops

rolmops

Posted
Posted

What really amazes me is that we talk about the engine as if it is just inside a car. This thing is in a boat and if it sets up or worse,there is no side of the road to move to. Instead,the people inside the boat are dependent on other people's good will to go out (possibly in bad weather)and get the passengers out of trouble.

FishingTheFL

FishingTheFL

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I've been stranded before. It sucks. I have a kicker so I wouldn't be stranded but I don't intend to use the boat now that its getting this late in the year and less people on the water.

I found a machine shop in Geneva that everyone says has a good price and I can watch the work as its being done. I guess now everything comes down to price. Its a winter project or a spring time sale. Its not a sellers market right now.

I'm going to rebuild the carb also. Kit with accelerator pump is $30 with taxes. The breather fell off the other day when I limped in. We re timed it yesterday and had a little issue at first with it dieing out ( sounded like it was sucking to much air), mechanic said that the acceleration pump was probably going or something could got sucked in and plugged the carb.

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Sk8man

Sk8man

Posted
Posted (edited)

rolmops makes an excellent point here that should not be taken for granted. A kicker is nice to have and can help out too but like most things you can't totally rely on it when the chips are down. In 2013 during the initial hours of the Lake Trout Derby my impeller gave out on the 135 while I was about16 miles from the launch and in 45 mph winds. My trusty 2 stroke 9.9 was put into action but the wind was so strong it overcame the 9.9 even at full throttle. I was forced to go into about 6 ft of water near shore and anchor up with 2 twenty pound anchors hoping to ride it out....wind shifted... didn't work....luckily my buddy Admiral Bird was near Sampson and was able to tow me back to the Chamber launch. Big lesson. Never forget that you can always be "vulnerable" out there under the wrong conditions no matter how prepared you think you are.

Edited by Sk8man
lakebound88

lakebound88

Posted
Posted

I don't know why you tried timing it again. The knock is a bearing issue. There is no avoiding it. Look at your old cam. The motor had issues. Still does. The more you run it the worse it's gonna get..

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Xxx

Xxx

Posted
Posted

For me there's no doubt that I would pull the motor and rebuild it. If the boat suits your needs? You have the lower unit rebuilt and you have new timing gears and new cam shaft and lifters, really you need some machine work, head, block, crank, ect. You have all winter to do it right. If the boat isn't worth it to you? There's always someone looking for a out drive you could sell. The more you run this motor the more damage your doing to the internal parts, and that's where the big $$$ comes into play. If Lake said its internal, him being a diesel technician or even higher up in the Diesel engine program, I'm pretty sure he's qualified to diagnose an internal knock on a gas motor. If you think you are capable of pulling the motor, and pulling it apart, that will save you a few bucks if this is the rout you want to take, then either have it assembled by the machine shop if they do that kind of thing or have someone put it together that knows what the hell there doing. Just some food for thought!! Best of luck to ya which ever direction you decide to go.

FishingTheFL

FishingTheFL

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Waiting on Barret for parts price. Machine shop quoted $80 to bore and hone. Pulling the motor out shouldn't be to hard. Neighbor has a chain hoist. Most likely go with the rebuild because of what I got into it. Got all winter to wait for the machine shop to get to it but sounds like it could be done pretty quick. Basically waiting on parts. I didn't ask them about cleaning up the crank but if their only charging me $20 a cylinder turning the crank can't be to much more. They were going to measure to see if it needed to be bored or not. As old as it is and the abuse its been threw I imagine it does.

I've learned a lot while doing this. Defiantly a good set of skills to have

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lakebound88

lakebound88

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Honing and turning are two totally different types of machining. Honing is cheap. You honestly can do that with the right tools from the comfort of a garae, but turning a crank gets pricey quick. You also can't get an appropriate price on parts until measurements are made, examples, cyclinders new bore size, cranks new diameter once turned. These items, once done require different size pistons and different size bearing to accommodate the material lost to create that thousands of an inch gap it requires.

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FishingTheFL

FishingTheFL

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How hard is it to upgrade to a v6 in aluminum? The mounts are what mostly worry me. I was told all the holes in the transom will match up. Also warned about the weight difference but the boat I'm getting out of it is also a 18' fiber glass. Its a 305 or 350. They say 305 but pretty sure its a 350. Comes with the out drive, no milk in the oil, I worry about the exhaust manifolds and elbows. Any idea how to check them without taking them off? I imagine their bad since the motor hasn't been ran in "few years". The other thing I'm worried about is if they winterized it. Any way to check with out dumping all their anti freeze out? I'm getting it for real cheap. If it works out I can sell my out drive to cover the cost of the whole motor and out drive. Mostly worried about the elbows and manifolds... They can be expensive

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Shellback

Shellback

Posted
Posted

Pretty sure 305 and 350 motors are V8's. Honestly, unless you have a damn good mechanic who will work for free, it's probably better for you to cut your losses and move on. 

FishingTheFL

FishingTheFL

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Pretty sure 305 and 350 motors are V8's. Honestly, unless you have a damn good mechanic who will work for free, it's probably better for you to cut your losses and move on.

Ah yeah throw $2000 away? You got $2k to throw in the trash... If you do please send it my way... Even if it don't fit... The price I'm getting it for is only $250, I can sell the motor, the out drive, and the trailer and still be ahead even if the exhaust manifolds are bad... Even if i pay the $1500 for the motor to be repaired... Its cheaper then buying a bunch more headaches... As far as the Hull, its old thick aluminum... No leaks... I don't want the aluminum of today, or fiber glass that is wood, fiber, and resin that wills rot. So yes its worth putting another motor in it... The floor replacement is easy, and I use to paint for a company that restored Tractor Trailers, beer trailers, and pick ups... Paint is no problem...

Pulling a motor, putting it back in and aligning it doesn't look that hard...

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