Advice on a 1973 70hp Chrysler (Pictures Added)

So here is the story. This may be a little long, but it will help to understand the issue I am faced with. I am looking for advice, what ever it may be. Those of you who have gone through this, and even if you have not. I just need to make a decision on what to do.

So last year my wife and I had a mini-van that ran, but was running ruff. I am not a car mechanic by any means, but I do know my way around an engine. I personally do not like cars because they are much bigger, heavier, and more complicated that small engines. Yes, I do understand the difference between 2 stroke and 4 stroke, so that helps with working on outboards.

So the story goes that we no longer needed the van, it was paid for, and so instead of trying to fix it up and sell it, I decided I might try to trade for a boat that I could fix up. It is smaller, I could tinker with it as I had time, and so on and so forth. Low and behold there was a guy that needed a minivan for his wife, and just so happened to have a boat for trade. I thought what the heck.

Went over to his house, well, not his house, but where he had the boat stored. And we looked it over. It needed some work, but it had real potential. The outboard looked good, but not being real familiar, I did not know what to look for. Boy do I wish I knew of this site before I had made a decision.

After deciding the boat would be worth fixing up, we turned our attention to the outboard. He assured me it ran, saying that he had it out on the lake not too long ago. He also said that he had just bought a new/used lower unit for it and was still under warranty. Just to make sure it ran he fired it up for a sec and then shut it off. I know at this point that doing that is not good on the engine, but I did not think of that then, and it was seriously only for a sec or two. But I am not claiming any excuses for my stupidity.

Knowing that it started and ran was usually half the battle when it comes to two strokes, made me decide that even if it needed a water pump, fuel pump, plugs, etc., that it would be worth the trade. So out of pure blindness, and ignorance of what to look for, we made the trade.

Took it down to the lake later that day and could not get the thing to run. lol. I was really second guessing my decision. I know at this point that most people would be calling the guy up and demanding that he trade back. But knowing what I might be getting into, I did not. I also know that if I was wanting to check it more I should have before I signed paper work, and bought the boat "as is". I would like to say that I am a man of my word even when others are not. Even though I know I screw up on that at times.

I then decide I will bring it back home and do some deeper looking before I jump to any decisions. I start with sticking a hose on it and starting it up. It starts but then dies. I see water coming out the exhaust, so I feel pretty good about the pump. However, not knowing why it died, I try starting it again. Will not start. After a little bit of checking I come to the conclusion that it is the fuel pump that is not working, because if I take the time to go and prime the carb bowls before trying to start it, it will then start until it runs out of fuel.

Simple enough I thought, I will just order a fuel pump kit, half way expected to have to do that anyways. But, knowing I would be ordering parts, I decided to look at the lower unit. Under close inspection, I notice it is taking on water. Long story short, I order a seal kit for it. I went through the process of taking it back to the place where he had purchased it, seeing how he said it was still under warranty. Which, it was, but they were really lousy people, and it sat long enough "before they could get to it" until it ran out of warranty. However, they said they would honor their warranty, but upon removing the prop they saw fishing line and said that they would not do any more with out payment. Not wanting to fight with them about it I just took the boat home and parked it.

That brings me to this year. I ordered the parts to fix the fuel pump and lower unit last year. Too disgusted with the whole ordeal, I did not even touch it until this spring. I first decided to tackle the lower unit. Did that this last weekend, took it all apart, replaced all the seals, water pump looks good, put her back together and fill with oil. I felt, still feel, confident with it at this point. So with that under my belt I dive into the fuel pump.

That brings me to yesterday. I took the fuel pump apart on Tuesday, noticed that the valves were not working, and one was completely broke, and got on here to ask some questions. Upon looking harder at the situation, and the different posts on here, I decided while I was at it, I had better check the thermostat. That brings me to last night and my quandary.

Hope your still with me at this point. I did not get home till after dark, but I have a work light I used to take the bolts out of the cylinder head and cylinder head cover, which is necessary to take both off to get to the thermostat. Well, just the cover has to be taken off, but in order to take it off, you remove all bolts holding the head on. So they both wind up coming off.

Upon removing the bolts I was noticing that they were corroded at the point where they were in contact with the cylinder head gasket. I thought that it was odd, seeing how the gasket should keep any water away from them, and it was only at that point they were like that. They came out alright though. After that I took the head and cover into the shop to take the cover off to get the thermostat out. After I broke one, of three, of the bolt heads off, I realized that they were corroded also, just a lot more. It was obvious that the head had come off the block, but the cover had not ever come off the head, because the original paint had not been broken from the cover and seal.

I am not too concerned about the bolts, I have removed ones like that before. What concerns me is that when I thought "hey, I'll go look at the cylinders while I got the head off", I did go look, and was sickened by the sight.

What I saw was disgusting. It was dark, but I do not think it is going to look any better in the light when I get home tonight. One cylinder looked good, the middle looked rough, and the bottom looked different than the first two. I will hopefully get some pictures to show soon. The cylinder that concerned me the most (they all do to a degree) was the middle one. It had a few large gouges down the wall running front to back. They were deep enough to catch my finger nails in them.

The reason I make the distinction about them running front to back is because there were others that seemed like, though I cannot say for sure, but they seemed like someone had rotated the drive shaft to bring the piston down as far as they could, for each cylinder, and one by one tried to "hone" the cylinder. The reason I say that is that there are "scratches" that run in a very, very irregular circular direction around the top 1/4th of the cylinders.

So that is where I am at. I am not sure if I should just replace what I have right now, put it back together, and run it like it is until I have time to fix it. It did start and run, But I am willing to bet that it will not have the power of a good cylinder. I am not too concerned with that though at this point. I just want something that will push the boat on the lake to fish with.

My other option is to take it like it is and work on it like it should be. I feel like it is fixable, but I do not know if it is worth the time. If someone has had this issue before I am all ears. Is it worth fixing? What else is there to look for? So on and so forth. Please lay it out for me and let me know what your advice is on this. I think I have covered the questions that may arise, but if not, if there is something else that would help to better give advice, please ask and I will find the information for you.

Thanks guys, I know that there is a world of wisdom on this forum, just hoping that you will impart some on me.

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

One more thing is that I did not do a compression check before I took the head off. I wish I would have, but I did not. However, I got to thinking that even if I did it might not be accurate anyways. If there was water and oil leaking from the gaskets to corrode the bolts, then air could escape also and would throw the reading off. Is this correct?

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

It's almost 40 years old how much do you wanna spend.You think you can find parts for that 40 year old motor???
If you can take it back.Quick ,fast soon!!!!J

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

Cannot, will not, take it back. I learn from my mistakes, not try to make excuses. I am not the kind of person that gets the short end of the stick and turns around and says "its not fair".

If I had spent the time into looking at it the way I should have, then I would have found these problems. He did not tell me he was selling me a brand new boat. Therefore, "as is" means "as is". Period. Now, if he would have said "bring it back if it turns out not to work", then I would have. But it was my risk that I took.

I have one more thing that might help diagnose the situation. The pistons run up and down freely, very freely, there is no hesitation or anything. So they do not "catch" on any of the groves. I still wish I would have done the compression test, because I am willing to bet that it has decent compression just from the 'turn over' that took place when rotating the flywheel with the head on and plugs in.

I do hate the fact that it is 40 years old, but if it can be used for a couple of years or longer it is worth spending a little time. I am curious if I couldn't "hone" the cylinder and put new rings on it and run it fine for a while.

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

I have 1971 70 Hp Chrysler and it was bad shape when I got it. It did not run. I took it apart and hone the cylinders a bit. Do not expect perfect honing on the cylinders. Just hone a bit to get to the point of happy medium. I had reused the rings did not buy a new ring set (hard to find). It got a decent compression and was working for 4 years. I bet your rings stick on the cylinder. Do a bit de-carbon and clean up the cab. It will run. It is a simple engine and easily to fix. When it runs it will run good. My engine never gave me a problem and I did not spend money and time on it since it was old. Your engine is running is a good start. Use sea-foam to get all carbon out of cylinders.

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

Thanks for the encouraging words.

It may seem funny, but there is not much carbon build up in there. I attribute it to the gaskets leaking a little water in there. I know its a crazy thought, but I have heard of where you can de-carb a engine with water, as long as you do not hydro lock it.

The pistons themselves look really great. I will hopefully get a better look tonight and some pictures to post. That is what I am thinking though; taking out the pistons, cleaning them, honing the cylinders, dressing the ports and sticking her back together.

Like I said. This is not a boat I want to ski, or tube, or try to run 0-60 in under 5 sec with. It is simply something that will push my little 15 footer bass boat to some fishing holes. At most I am going to guess I will want to go 20 maybe 30 mph. I dunno. Either way, its old, and I am not going to dump a lot of money in it to overbore the cylinder and buy new pistons. If they look good at most the only thing I am going to get I think will be rings.

I am seriously still looking for and wanting opinions on this. Pointers, experience, so on and so forth. Learning from experience has always been best for me, but a little help is good too.

The bright side is that a guy I work with has a 72 Mercury 50hp that he is willing to let go of for 200. Sounds good, but I think I will take a pressure gauge over there just to make sure. lol.

All in all, it is almost impossible to know for absolute sure what you are getting I think. You could do all the tests you want on a motor, but unless you take it apart and look at it visually, you will never know what could happen when you run it for a little while.

I am sure that with the experience that is on this board there are a lot of things you can do to make it a wiser purchase. Those things are what I am looking for.

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

"72 Mercury 50hp that he is willing to let go of for 200" it sounds good. I 'd like to take it if compression good. Make sure you have all control parts with the engine. I have 73 Mercury 40 Hp which I am working on. It has good compression but no spark since all the wires were corroded.
Just take Mercury and put on you boat then use your spare time to work on Chrysler. Make Chrysler as your spare and back up engine if Mercury went bad.
You still recoup $200.00 back if you part out 72 Mercury.
Let me know the outcome of the deal.

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

I have the exact same engine. I really like this motor. Its needed some work, new head due to 2 stripped spark plugs, I replaced water pump, all LU seals last year, new CD Module (I fried it).

Late last year, it was really hard to start. Took to a local shop and he said, its probably a choke problem. Sure enough, they were completely out of whack. He adjusted them and when I took it out on the water two weeks ago, it fired up first crank.

I would not get discouraged. My compression is 115-118 and it still is pushing me to 27 mph on gps. I use a 50:1 oil to fuel, I do my best to take care of it and I expect this to last a long time. If it comes to it, I'll get it bored out before I buy a new motor. Don't worry, be patient. These are really good motors, albeit the choke is sensitive. Hope it works well for you, take your time you're doing it right. Maybe get the cylinder honed and the carbs adjusted properly. Don't want to run those cylinders lean.

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

Yea, it does sound like a heck of a deal. I told him I would try to get the money. I just wish it was easy to convince my wife that I need these things.lol. I will say that before I buy it the first thing I will do is a compression check.

All in all I think it would be a good deal. I did some searching however just a bit ago and found someone that has a boat, motor, and trailer they are wanting to sell. Not sure if it has been picked up yet, but the neat thing is that it is a 90hp Chrysler, and looks like the same style I have. Never can be positive on that sort of thing. But they are only wanting 100 buck for it all. I will be surprised if it is still available.

I will keep all updated on progress of this venture though. Hopefully it will be useful in the future for someone.

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

You're kinda like me..
Likes to open a can of worms........

If it were me.
I'd tear it down, and hone the cylinders out. You're not gonna get rid of a huge scratch unless your bore the cylinder. Then that's too much.
Take a peek at the rings. IF they look good I would reuse them. Take the Pistons out and soak the ring ends in a mineral spirits. If you have or can rent a few tools. Rent the ring pliers to remove them Then you can clean the grooves of of the pistons.

You probably can get the seals, gaskets and rings if needed from http://www.laingsoutboards.com/

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

Took a good look in the daylight yesterday. Not as bad as my mind was telling me the night before.

There are some definite abrasions on the inside of #2 cylinder, but they are very, very, shallow.

My fingernail does not "catch" them, I can just feel them with it.

I definitely think that pulling the pistons and honing the cylinders is the way to go.

I am pretty sure I will find the rings are shot, or not even there. Anyone have any good suggestions on new rings?

I wish I could find a site that shows a blow up diagram of my engine, or one pretty close to it, so I can find part numbers and such. Anyone know of any sites like that? Or what year and hp my motor would most closely stick to.

Thanks for the help guys, keep it coming. Hopefully pictures will be up soon.

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

I have a 1970 55hp

http://www.laingsoutboards.com/
I called them and he's got everything I need. I'd give him a call.

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

Well, took the kids fishing in the daylight, which ment that I didn't get much done on the motor tonight. But curiousity got the best of me and I hooked up the light and commenced to take off the carbs and reeds.

I was a little weary when I saw that they had been taken off before. But was pleasently supprised at the look of them. They were very clean and not showing any signs of wear.

I am kicking myself for not taking pictures of before and after. But before I do take the pistons out I will take pictures. Took a flashlight to the back of the pistons, through the reed openings, and all looks good so far.

I got to thinking that someone might have already done a bore job, so I took the calipers to the cylinder. 3.115, but that was at the very front where there is a little build up. I think it is safe to say no one has done one, but will know better after I pull the pistons tomorrow.

I will definitly be posting pics tomorrow, so you guys can take a look and post some opinions.

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

Long? Nathan, I grew a beard while reading it! LOL

I could be wrong, but I don't know of any Chrysler three cylinder engine with that bore. To the best of my knowledge, they were all 3.3125. Wear, taper, and out of round tolerance is .002.

Chrysler only used two bore sizes on the larger engines: 3.3125 and 3.375. The next step down was 3.187 on the two cylinder single carb 55.

Those 3 cylinder engines were nice--not powerhouses, but good engines nonetheless. In my opinion, it is worth the 450 or so bucks (pistons and overboring) to rebuild it. You can even re-port it to make it an 85--not a difficult job at all if the engine is apart for boring.

Re: Advice on a 1973 70hp Chrysler

Re: Advice on a 1973 70hp Chrysler

Lol, I probably could have gotten by with not so much info, sometimes it helps to vent. My wife says I have a habit of rambling on.

I fat fingered the reading I typed last night, I meant 3.310. Who knows why it put down what it did. I was typing it on a screen that is no bigger than your hand though. Sorry for the confusion.

I have all the specks for bore size and piston size printed out. My main concern was whether or not it had been "honed" or even bored out before. It seems as though if it had been honed, it wasn't enough to make a difference. I know that the 3.310 is a smaller size than it should be, but I believe it to be build up on the part I was measuring.

I thought about the re-bore job and all, but right now I just do not have the money to sink into it. But I am feeling more confident with it, so maybe in the future it is something that I might tackle. As far as I can see the pistons are looking great, so it is looking like a ring and hone job at most. If I pull the pistons and find that the rings are in good shape, tolerances good and all, then it may be just a good cleaning and hone job. Either way, I need to hone it, I just do not like the way the cylinders look, and I have it this far apart anyways.

In between rain showers I was able to sneak out and get some pictures. So as promised here they are. If there are any other pictures that someone would like to see for what ever reason shout back and I will try to accommodate you.

Re: Advice on a 1973 70hp Chrysler (Pictures Added)

Certainly not what you want to see, but I've seen worse cylinders and they still run good.
Pull it apart and hone it out to get a nice cross hatch. Order up a set a rings and gaskets and let her rip.

Re: Advice on a 1973 70hp Chrysler (Pictures Added)

Yeah! That doesn't look too bad--even without honing it should deliver decent compression.

It certainly does appear that someone tried to hone it with a coarse stone. So, if it makes you feel better, try to use a fine stone hone on it. If you have never honed a cylinder before, do NOT use a bottle brush hone. Use a three stone hone like the one you can buy at Sears. Use LOW drill speed and move the hone in and out at such a rate as to get 60 degree crosshatching. There is a land at the bottom of the cylinders so be carefull. This land is about 1/2 inch below the cylinder liner itself so don't go too deep. It is possible to break the stones if you hit it. Try to only remove a couple of ten thousands. .0001, .0002, etc. Remember, there is only .002 limit for wear, out of round, and taper. Sure: if you go past this, the engine will still run, but not at its best, and these old Chryslers were rated at the block so they put out less HP to start than you expect.

Notice in the third and last photo how the exhaust ports do not reach the top of the piston at bottom dead center? They are small and this is one of the ways the engine is limited to 70 HP. IF you take apart the block to hone the cylinders, extend the ports downward to enlarge them. You will gain a couple more HP. Now, if you want to port the engine and square both exhaust and bypass, you can gain up to 30 HP. Attached is a photo of a ported 90 HP 3 cylinder showing the bypass side. Exhaust is basically the same and you can see some if you look through the bypass ports. While it still did not perform like a Merc, it did equal a Chrysler 105 in performance. (Note that the Chrysler 105 actually only produced about 90 at the prop. It was later downrated to 90 when the whole industry went to prop rating)

Re: Advice on a 1973 70hp Chrysler (Pictures Added)

Thanks guys for the advice.

Half of me says pull the block off, the bigger half says leave it on and do the basic. The sound of porting and all sounds REALY good.

It will wind up being the simple approach because of time issues. But I am going to keep that idea in mind for something my son and I could do together when he gets older.

I will definitly clean up the ports while the pistons are out. Will I run into timing issues after all of this? I am mechanicly inclined, but I do not like supprises.

Hopefully I will get the pistons out today and get some pictures of them up here.

Re: Advice on a 1973 70hp Chrysler (Pictures Added)

LOL man , I just took at least 20 minutes to read all this!

Looks to me like the guy just used some sos pads or something to try an hne it out! LOL A good hatch should bring most if not all that out buddy. At least good enough to get it to do what you are wanting to do. They dont look all that bad really.

You seem to be unlike most though, being honorable and learning from your mistake is a huge reason I did keep reading. But a word of advise, DO NOT start taking things apart like you did here and fixing more than one thing at a time. I know it sounds weird at first, but by doing so one little mistake will leave you completely lost.
What I mean is do the fuel filter or pump...then do spark plugs...then do whatever next...get it? If you do all three at once then take it out to the lake and she dont start you have no idea where to start...hope you understand. Oh yeah, and I know how things are, but a man who takes apart a motor and does not take extreme care in labeling every single bolt and its location is asking for problems when he does not put it right back together. i have kids to and know how they just love to mess in daddy's stuff!

And that other motor...yeah its a good price,if everything comes with it. But if you did buy it I would set it aside and not even touch it till you get this work done. Otherwise it or this will get put on the back burner and left behind. And if you do indeed go buy it...take the guage. LOL Good luck!

Re: Advice on a 1973 70hp Chrysler (Pictures Added)

Are there any tips or tricks to the actual piston removal from the cylinder? Just thought I would ask in case someone had run into an issue they wish they would have done differently.