1970 MERC 1350 having trouble!

[overkillthemighty]

I am a novice to boats, though I have a fair amount of experience with cars and engines. I bought a 18' boat with this engine for $300. The boat needed a lot of work, but the guy said he brought it to a shop and the engine ran fine (the wiring harness was cracked and gone, but I built a new one). I got the engine running, found that one of the sparkplug wires was not connecting and fixed it. After getting the boat and engine in good enough shape I put it in the water and hit a top speed of 45Mph (GPS Speed, the speedo was dead), and ran it for a good 2 hours with no trouble.

My trouble began 2 days ago. I took the boat to a different lake for the 4th, and it was not acting normal at all. It started harder than usual, but I thought it was the higher elevation. As I started out into the lake the engine did not seem to be pushing nearly as fast as usual, and a couple of minuets after I left the marina the engine started putting out a little smoke. I was hoping that it had sucked up some oil and was just burning rich, so I swayed a bit to try to get the tank to slosh, but the smoke started getting worse, so I cut it.

The top two cylinders were boiling water off when I flicked some on them, the middle two were steaming a little, but not too bad, and the bottom two were just a little too warm to touch. Also, when I first pulled the cover off, there was some smoke coming out of the middle carb. One of the spark plugs was not tight enough and some oil had leaked out of it. I pulled the 5 easily accessible plugs and they all looked a bit dry to me. I put them all in and tightened them properly. I cooled the engine down with a small drizzle of water down the heads, and when it stopped steaming I let it sit for a while. After waiting about an hour I headed back toward the marina at about 1/3 throttle (I pushed it up to full after a bit, and it seemed faster than before, but it was still only going 17 Mph) when I got near the marina I trolled around for a bit to see if the problem was a fuel mixture problem, but after about 5 minuets, it started smoking again. I cut it, cooled it, and headed back to the marina. I docked it and got the boat trailer, by the time I got back, the engine had a really hard start, but I got it up and on the trailer.

There are a limited number of variables between the last run and this one. The altitude difference between the two (The second lake was 1700' higher than the first). The fuel mixture (I did not have a can to pre-mix in, so I dumped the oil in and added the fuel after, but I then drove a good 60 miles, so it should have mixed up). Last, but not least, the engine ran for an unknown amount of time at idle without water (I had the earmuffs on and was trying to fix an electrical problem caused by the colossal amount of electrical noise the engine makes. It ran for a total of 2 min, and some time during that run some jerk tripped over my hose and didn't say anything about it or fix it.)

I feel that it is the last one, but I need to know where to go from here. People say it is not worth it to rebuild the lower unit, but I am on a university student budget and have time and some resources to work on it. What can be done? What needs to be done? Is it likely the engine is burnt up (will I have to pull it apart and look for scoring?) or is it more likely to be the lower unit? I am really prepared to pull the whole thing apart and try to fix it, but I need help knowing what to do. I have a service manual for the engine (That is how I rebuilt the wiring harness). Will that give me enough detail, or will I have to get additional info? I had called a few shops around here a while ago, and they all said they wouldn't even touch an engine this old, so I am on my own. Any help would be much appreciated. Again, this is my first experience with owning and operating a boat, so sorry if I did stupid things.

 

[MACH1SCJ]

Re: 1970 MERC 1350 having trouble!

I'm a novice at boats too. ---- Boiling on top -- sounds hot -- ran with no twater to pump---suspect waterpump failure or at least weak. --

You need to check compression first, that will tell you if you did damage to the powerhead. If compression is ok then I would replace the waterpump & try again.

Was the telltale (pee hole) peeing water when you were running on the lake.

 

[mr 88]

Re: 1970 MERC 1350 having trouble!

Hope you did not fry it. Sounds like your impeller is shot or partially working. Any water coming out the tell tale???Small water outlet under the lower cowl,thats what its there for,the majority of the water goes out the prop to help muffle the engine,but the tell tale is there for you to observe while under way or at the dock,lets you know it's pumping. That should of been the first thing you changed before trying to start it.Sometimes the impeller blades disintergrate slowly and you may have some small chunks in the passageways or it is only pumping a small amount of water with whats left of the impeller. Your manual has all the answers, if you are pointed in the right direction. If you can, run a compression test before you put a dime into anything else,then report back with numbers. There is no cylinder head or gasket that can be replaced,it's all one piece.If you did not seize,scorch it there is good chance that it will come back to life. The 135 is a strong runner,basically a de-tuned 150.Do not give up,they are relatively easy engines to work on,especially with a manual....

 

[overkillthemighty]

Re: 1970 MERC 1350 having trouble!

Thank you for your help! I really had no idea what I was doing or what to look for. I did not realize there was such a thing as the telltale (I have searched for pictures and I think I know where it is on mine), so I did not notice if it was going or not. I did do a compression test when I first got it, and all cylinders were within 10 psi of each other (I want to say around 70?), though I am not sure I was doing it right (I pulled all the plugs and hand cranked it about 6 revolutions per cylinder). I also have been mixing the oil a bit heavy since it is older, I figured it would help it stay lubed up. I will try starting it today after work and check if the tell-tale is working. are earmuffs enough, or should I get a tub?

 

[mr 88]

Re: 1970 MERC 1350 having trouble!

You have to turn it over with a battery,should be 110 to 140,she is a bit old so as long as the numbers are close you will be good. Hopefully you did not fry a bearing,check it [ compression ] again.Yes you can use muffs to check the tell tale. There is a black hose that goes from the top of the block to the lower shroud and it dumps out there.Sometimes that clogs up with crap,a quick poke with a zip strip or something like that may clean it out if it's plugged,water should also come out the prop.If you get her running you can use Pennzoil synthetic at a 50:1 ratio with no problem and it will run cleaner.Too much oil hurts the idle circuit and you may foul a plug. Compression will be a good indicator of the condition she is in.If good then move on to probably the water pump assembly,many if not all these parts are available from NAPA if you are not near a marine store and priced lower.

 

[overkillthemighty]

Re: 1970 MERC 1350 having trouble!

I grabbed a compression tester from the auto parts store to test it again. I heard you should warm the engine a bit before checking compression, so I put the muffs on and ran it about 45 seconds to a min. (no water thru the tell tale, and no water out the exhaust unless I squeezed the muffs really tight). Afterwards I pulled all of the plugs out and resistor grounded the plug wires. I put the tester in each cylinder and cranked it for about a 4 count. I tested each twice and here are the results:


1 - 49, 45
2 - 57, 49
3 - 60, 54
4 - 45, 46
5 - 54, 53
6 - 41, 46

That sounds kind of bad to me. 4 and 6 look a bit low. Is there a way I can improve compression in these engines? (I have heard my father talk about a process where they can put a thin layer of some sort of material on the sides of the piston to make them fit more tightly, or perhaps new rings?) I realistically am willing to rip this engine to its block if i need to (I could use a winter project!) Where are the bearings, and how to I check their condition? I have never taken an engine block apart myself before, but I am willing to if I need to. I will try cleaning the tell-tale (which strangely enough appears to be connected to the bottom of the block), but I am sure the pump needs servicing anyway.

As far as the pump goes, should I be buying something like this: http://store.oldmercs.com/product_p/46-96148a8.htm or do I just need to get the impeller? I don't know much about the history of the boat, and I don't know if it has been serviced, or how often. If you have a suggestion for where to get a bare impeller (if that is the best/cheapest reasonable route), that would be cool too. I know there are 2 different ones (High pressure (mine), and High volume), but I don't know what the part numbers are for those two. Thank you all so much for your help!

 

[mr 88]

Re: 1970 MERC 1350 having trouble!

You cooked the rings if not the pistons,bearings,rods etc and hopefully not the cylinder walls. It's worth rebuilding if the holes are not scored up.You can buy NOS piston kits, probably 70-90 per hole or go used with new rings and gasket kits. Some special tools are needed ,unless your creative with what you have and that better be more than a craftsman 200 pc set. Anyway if you decide to do it,buy a Seloc or Factory manual to get you started.Most 1500/1400/115 share the same block but you have to be aware of bolt patterns where it hooks up to the mid as they can be different. You might be better off scouring Craigs for a working Tower on a boat or by itself and pay 200-500 for that.Sorry about your learning curve results.Hindsight,should of asked here what to do before turning the key with a old motor that has not been run,maintained,water tested etc. You may want a second opinion and take it to marine/ auto shop for a compression test just to double check the accuracy of the "loaner" one you used,as those can be out of whack as well.

 

[Faztbullet]

Re: 1970 MERC 1350 having trouble!

You might be better off scouring Craigs for a working Tower on a boat or by itself and pay 200-500 for that

110% agree....

 

[overkillthemighty]

Re: 1970 MERC 1350 having trouble!

You cooked the rings if not the pistons,bearings,rods etc and hopefully not the cylinder walls. It's worth rebuilding if the holes are not scored up.You can buy NOS piston kits, probably 70-90 per hole or go used with new rings and gasket kits. Some special tools are needed ,unless your creative with what you have and that better be more than a craftsman 200 pc set. Anyway if you decide to do it,buy a Seloc or Factory manual to get you started.Most 1500/1400/115 share the same block but you have to be aware of bolt patterns where it hooks up to the mid as they can be different. You might be better off scouring Craigs for a working Tower on a boat or by itself and pay 200-500 for that.Sorry about your learning curve results.Hindsight,should of asked here what to do before turning the key with a old motor that has not been run,maintained,water tested etc. You may want a second opinion and take it to marine/ auto shop for a compression test just to double check the accuracy of the "loaner" one you used,as those can be out of whack as well.

I will try to get the compression checked again, but two different checkers gave very close results, so I am thinking I am out of luck that way. I am planning to rebuild the beast. Looking at it, worst case (fixable) scenario, it will cost around $1000 for me to rebuild it. (Kit + machining with luck). I will pull it apart and check how much damage there is in a month or so, and post here. If i do rebuild it, I will most likely take tons of pictures and post about the experience. Should be fun!

 

[overkillthemighty]

Re: 1970 MERC 1350 having trouble!

I decided to rebuild it, and my thread is HERE. It may come in handy, and one of the links has pictures to how the engine was set up before I took it apart.

 

[Dave1027]

Re: 1970 MERC 1350 having trouble!

I think you would have come out money (and motor) ahead if you would have done some simple things apon taking ownership like rebuild the fuel pump and carbs and replace all hoses and wiring. Hindsight is 20/20.