Mercury outboards

[~Nickolas~]

Hi all,
I am curious as to if any other motors are built like Mercury's are without a removable head. Last year when I got the Silverline boat that came with the 115 Merc inline 6 this was my first Mercury engine. All these years I have had Evinrude motors and then got an old 56 Johnson along with a Chrysler and a Force that came on a Bayliner. Anyway it was odd to me that this engine didn't have a removable head as the other's. I have done a lot of reading on outboards and see that Mercury is different and you can't just open a toolbox to fix it like an old OMC motor. Do you need a tool to compress the ring(s) when installing pistons in this engine?

I ask because I was rebuilding an old Homelite chainsaw the other day and it is made with a taper so when the piston goes in it compresses it right before going into the cylinder and just slides right in. That was too easy to put back together and now it runs great. So is the Mercury like this or do you need a special ring compressor to do the job? I've read certain motors need special tools unlike an Evinrude where you can open your tool box and pretty much grab any tool you need to repair one of these motors. I see Mercury is different from the other's but so far the few things I have done to it were just as easy as the Evinrude.

I also like the design of the gearcase with the hole for the speedo. This is the only boat I have out of six with a pressure system speedo that actually works. None of the speedo's work on the other boats with the pressure head and Pitot on the back of the boat. Not really a bif deal but it's nice when things work. Carbs were easy to rebuild as well as installing a new water pump. Maybe if and when I get to the engine block things will change but so far a breeze as any other outboard. I like the gearcase setup also with the short splined shaft instead of a long driveshaft to pull out and put back in that's much easier to deal with. Anyway the block without a removable head to me anyway is really odd. It does run well though out in the water. This engine is 31 years old and very clean so it probably has low hours. I got 150 psi on all 6 cylinders so it looks to be in great shape.

I am guessing a Mariner is a Merc with different clothes. I have never seen a Mariner outboard but all I read says it's a Merc of a different color. Originally a saltwater series engine I think is what they were designed for? All other engines I have messed with have a removable head just like an automobile engine. I have really grown to like this engine with it's power and torque and man is that sucker LOUD. I had the top up on the boat the first time I took it out and couldn't believe how loud this motor was. She was talking at WOT out in the river. Looks pretty impressive back on the transom too. Only thing is this motor is a very thirsty beast. I guess I need to learn how to keep backed off the throttle but I do love my speed.


Nick

 

[Chris1956]

Re: Mercury outboards

Nick, A Mariner is a grey Mercury motor, as you have guessed.

Merc motors may be serviced without special tools, for the most part. The gearcases do require some special tools(i.e. a gearcase nut spanner), but the balance of the motor can be serviced with normal tools.

When I rebuild my Mercs, I remove the crankshaft from the connecting rods, carefully keeping the rod cap and bearings together for each cylinder. I use 6 small cups numbered 1-6 to do that. Do not reuse connecting rod cap screws. if you have the older bolts and nuts, they may be reused.

I install each piston individually using my fingers to compress the rings. When they are all in, I use some grease to hold the connecting rod bearings in place while I bolt on the rod caps.

 

[~Nickolas~]

Re: Mercury outboards

Sounds easy enough... I don't need to get inside the motor yet but just more curious than anything. All I had to do was the impeller and carb overhaul so far and she runs great. Just a PITA to get started that's the only issue I got with it. But when spring rolls around I have an enrichment valve to put on it so that should take care of that. Don't think the gear case needs to be re-sealed yet. I re-sealed the case on the old Chrysler and that was real easy. Just a tool here and there and it will be just as simple as the other's. I do see though the reeds in this motor are set up a whole lot different than what I am used to. Looks like you have to tear down the whole engine and remove the crank maybe to replace them???

 

[Chris1956]

Re: Mercury outboards

Yes, you must remove the powerhead and split the crankcase to get to the reeds. The good news is that very rarely do they need replacing.

Remember to replace the impeller every few years, including gaskets and wearplate, change the gear oil at least every fall, use fresh premixed gasoline and hit the grease fittings at least every year.
Keep an eye on the carbs. If they get gunked up, you can have major issues. Usually using fresh fuel wil keep them pretty clean.

 

[~Nickolas~]

Re: Mercury outboards

That is odd to have to take the entire motor apart to get to the reeds. The reason I am curious is I have put in Boyesen power reeds in an Evinrude I have and really like the results they gave me. Real easy to do with removal of the intake and there they are but this Mercury has to have the entire engine disassembled? I think I'll just leave it be in case I get bored one day and just feel like tearing into an engine. A lot of people say don't waste your time and they don't do anything but I beg to differ. I noticed a very nice improvement in all aspects of how the motor ran afterwards. I'm glad I did replace the stock reeds as the motor runs much smoother. Anyway thanks for your input. I always replace the impeller every year or so along with changing gear case oil, greasing it and adding ethanol additive to each tank of gas so I'm good. I see a lot of folks saying also to run premium gas in these motors but I do mid grade and it seems fine.

 

[Rmoore45]

Re: Mercury outboards

Mercury was a pioneer in the business they were the first ones to develop exhaust through prop, rubber water impellers, and many other things that make outboards great today. If you want more history on mercury watch this playlist

http://www.youtube.com/playlist?list=PLE8CCDE8539503214

 

[gwukena]

Re: Mercury outboards

And a tower will dance around a johnnyrude v4 all day long. My 83 115 still will dance a new etec 115 all day, hole shot to top end, until I need to fill up.

 

[Chris1956]

Re: Mercury outboards

The Merc inline motors are real compact. On an inline six, the motor is really 3 two cylinder motors sharing a crankshaft and block. The reed blocks are donut-shaped, held captive by the crankcase halves and double as main bearing supports. That is why you need to split the crankcase to get to them. There is one reed block between cylinders 1 and 2, one between 3 and 4 and one between 5 and 6.

This is quite different that the johnnyrude design for cross flow motors.

 

[~Nickolas~]

Re: Mercury outboards

After installing reeds in the Evinrude 60 which was a breeze and looking at the design of the inline 6 motor it's a huge difference. I have no problem taking the block off and taking the motor apart to replace them if I was going to because it will get me more familiar with this engine. I actually will replace them sooner or later with aftermarket reeds as I want to put new gaskets in this motor anyway. It is nearly 32 years old and I doubt it has ever been apart. It wouldn't hurt to remove the exhaust covers and get them cleaned up real good and have new gaskets installed.

That is an interesting design with reeds being the intake system along with also being a bearing support. Next spring I'll park the boat and start this task of removing the block and taking it apart to do the gaskets and reed job. I always enjoy taking a motor apart and fixing or updating it for an improvement. I've been a mechanic all my life and taking things apart and fixing them is what I'm best at. Motors are a joy for me whether a pain in the rear or easy I always am satisfied when I turn the key and it fires up and runs. Learning to work on something new that I haven't worked on before is exciting and then when the time comes I can say I know what your talking about and I've done that. Might be able to help out a friend in need one day.

I see a lot of folks talking about running these motors at 40:1 and on 93 octane? Is it really necessary for either? I know gas is not as good as it used to be but oil is a lot better than it used to be so what's the issue? Do these motors have oiling issues or are folks just sticking to what was the norm back in 1970 and not want to change? Now I always use 89 octane with an ethanol additive and it seems to get the job done fine.I don't understand the oil ration unless the motor has an inherit issue in design. I run 100:1 Amsoil in my 1972 Evinrude 85 and it runs great. Idles better, starts easier, throttle response is better and less smoke and plug fouling.

We have a gas station around the corner that advertises ethanol free gas and with my test kit it shows a trace amount so it's worth .10 more a gallon to me. One other station advertises 100% Ethanol free so I filled it up one day and when I was out in the water the motor ran like crap. When I got home I tested it with my kit and guess what....... 10% Ethanol content!!! So don't believe everything you read or hear. I was going to go back and say something to the owner but decided I just wouldn't buy gas there anymore. Ethanol is BAD for an outboard and I treat my gas with an additive regardless of where I fill up. I still want to hear about the 40:1 oil ration though as I don't know why so rich.

Anyway I am getting to like these motors the more I mess with them and run them. This has to be the loudest outboard I have ever had. When me and my girl were out in the boat one day with the top up and I was near full throttle I had to yell as loud as I could to talk to her. But when I am by myself it is music to my ears and it doesn't bother me a bit. I love the sound of a screaming two stroke and the smell of the oil. This may turn out to be my favorite outboard in the future as I run it more...

 

[Chris1956]

Re: Mercury outboards

Run that motor at 50::1. No need for any other ratio. Make sure the max spark advance is 21* BTDC maximum, and you can run her on regular gas with alcohol or not, as is desired.

The water jacket covers and exhaust covers on that motor are famous for having the bolts break, when someone tries to take them out. if you are determined to do that (no reason I can think of to take them off a good running motor), use heat and penetrating oil to get them loose. Use a hand impact driver as well to coax them out. Prepare to break a couple of bolts.

 

[~Nickolas~]

Re: Mercury outboards

I appreciate your reply but my question still isn't answered. I want to know why 40:1 or 50:1 there has to be a reason when we have oils today that we can run leaner and still get the job done properly. As I asked is there an issues with design of this engine and this much oil is needed? I have had many people tell me to run it at 50:1 but I have yet to hear a sound reason for doing so. And as far as those bolts I was wondering about that. We had another motor with lots of salt water use and ALL of those bolts wrung off. But I do have another motor from 1977 that I got all of the bolts out without any heat. I had to put penetrating oil on two of them and the rest all came out with ease thank God. And that motor sat for 20 years in a barn.

A lot of people say if it ain't broke don't mess with it.... Well I would rather take it apart and have it fixed right and have those bolts clean and new with the proper goup on them so they don't seize up on me as long as I have it so if and when I do need to take it apart it will come apart like it should. I am going to test a few of them with a ratchet and see if they wanna budge or not then next time I go over to the house...

 

[mr 88]

Re: Mercury outboards

I run 40-1 on my 66 1100ss and 73 500.In the process of rebuilding a 140/150 and will run that ratio.If aftermarket reeds are available for the stackers design ,I would still stick with stock.Have you seen the reeds or a picture of them? They are not like most reeds on two strokes.Your compression is perfect so why tear it down.There should be a twisted wire going through a bolt on the side cover with a lead "tag" soldered on.If that's there then it has not been torn down.These gentlemen on here are very knowledgeable and will help you at every turn.I have found the older X-racers on Facebook to know these ol beasts like the back of there hand.Post up there on your reed question and you will get a straightforward reply...search icon on FB....inline 6 mercury outboard motor fans. The 115 is a great motor and depending on year may actually be closer to a 150hp.Loud yes, but then again you do not have to listen to anyone,including GF while your out at WOT,just the L6 singing!!! That's What I Am Talking About...................................

 

[Gomer50]

Re: Mercury outboards

The book say's 50:1 so 50:1 it is, turned the max timing down to 21 degree at WOT due to today's gas .I use mid grade fuel mine doesnt seem to like regular,I also use a double shot of sea foam for every 6 gallons and my 1978 90hp inline 6 is as clean as a whistle.Keeping your carbs clean and a good water pump will keep you in and on the water for some great fun..

PS: On a side note all these older Mercury's over time the wiring would deteriate and if not attended too would cause problems that can really become a headache troulbe shooting.

 

[~Nickolas~]

Re: Mercury outboards

There should be a twisted wire going through a bolt on the side cover with a lead "tag" soldered on. If that's there then it has not been torn down.

I don't see any twisted wire with a lead tag anywhere. Which side is it supposed to be on? Someone has written in white on the port side "89 whatever that means I don't know. As clean as it is you would think it has never been touched or maybe it has been and that's why it is so clean. But the guy did say it was in storage for years so that is another probability. From what I have read I don't think my motor is close to 150 but also with Mercury I guess you never know what block they may have used. All I seen on the side is a casting number of 352-7738 Serial number is 5725107 so 80-81 year from what I read.

It does run damn good and is loud as hell and I love it... I am the type to do preventative maintenance so I won't have any problems down the road. I know that side exhaust cover is probably a bit nasty inside and bolts may be stuck but I want to make sure it is clean and not clogged up with any crud. Thing is I have so much free time on my hands because I don't work anymore I want to clean it up a bit and re-seal it cause I have all the time in the world and it would make me feel better out on the water. I'd rather fix it now before it possibly goes out on the water and ruins my day ya see...

 

[gwukena]

Re: Mercury outboards

I wouldn't worry so much about the mechanicals on the towers, but be more concerned about the ignition side, ie: switchboxes, stator and ditch the idle stabilizer if not already done

 

[~Nickolas~]

Re: Mercury outboards

The book say's 50:1 so 50:1

You answered my question right there. So I know you run your motor at this ratio because of the manufacturer suggestion at the time it was made. Good I've made a little progress.

 

[~Nickolas~]

Re: Mercury outboards

I wouldn't worry so much about the mechanicals on the towers, but be more concerned about the ignition side, ie: switchboxes, stator and ditch the idle stabilizer if not already done

Yep the wire is showing a little fraying but not too bad. I don't have a stabilizer and am going to add an enrichment valve because when it's cold it is a real PITA to start!!!

 

[gwukena]

Re: Mercury outboards

Yep the wire is showing a little fraying but not too bad. I don't have a stabilizer and am going to add an enrichment valve because when it's cold it is a real PITA to start!!!

So somebody already removed the stabilizer/disconnected it? it's a little black box on the front cowl support. Even with an enrichener there's a knack to starting them. They like to have a lot a throttle to get going, and need to start pulling back on throttle as soon as they fire. Practice the technique and you'll have no problem starting her even with the rope

 

[~Nickolas~]

Re: Mercury outboards

So somebody already removed the stabilizer/disconnected it? it's a little black box on the front cowl support.

No black box and I don't think it ever had one. This is a 1980 model 115. I read they all didn't come with it like the enrichment valve. I am glad it is at least a 1980 because it has electronic ignition and not a distributor but I wish I did have a later model with integral tilt/trim...

 

[gwukena]

Re: Mercury outboards

Easy upgrade, I have an 83 that has been retrofitted. Have a trim and swivel bracket off of an 87 mariner 75hp installed, love it