91 Mercury 115 Rebuild - Let's see how it goes!

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Well now that's a coincidence! This is my thread that I started over a year ago. Then SUMMER HAPPENED! And also hunting season (got my 13 year old daughter into hunting with me and we got a turkey last October), and some other stuff. I just got back to chamfering the ports last week and I am ready to start reassembly. Recently inventoried all the parts I bought for the project (many from Faztbullet and here on IBOATS), reviewing the manual, etc. I just happened to check the forums and found that beatoangelo resurrected my thread almost to the day that I got side tracked!

I'm hoping, depending on the weather, to do the final cleaning of the block this weekend outside before I start reassembly. I'll start posting pictures again as I reassemble.

One thing I found when I chamfered the ports is that ALL three of the cylinders I had honed had a good burr on the ports. The honing looked just right and the cylinders are in spec. The cylinder I had bored/honed did NOT have burrs. How could that be? Did it come from the factory that way originally with burrs on all four cylinders? Or when it was rebuilt the first time? In any case, I think I have them all good now. Took me about 4 evenings to get them all cleaned up the way I wanted them. Used a lot of different bent files, dremel tools, and abrasive papers to do them.

Anyway, I'm making progress again!

 

[Yesterday]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Awesome! Looking forward to watching your progress!

 

[Hamo1]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Been waiting half way round the globe for this thread to start up again...LOL

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Scrubbed out the block thoroughly today with hot water and detergent a brush and sponges. It appeared that in just a few minutes after I was done I started to get two streaks of flash rust forming in two of the cylinders. When they say oil the cylinders immediately they aren't kidding. Rubbed real hard with an oily paper towel and rubbed it off.

Hopefully tomorrow I can start reassembly.

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Well, I had second thoughts tonight about my scrub job. I went and checked the intake ports (behind the sleeves) for Cyl 1,2,3. All were clean. Then I checked Cyl 4 (the one that had the melted piston). See the picture for what I found. I think this is some of the vaporized/burnt aluminum from the piston. I think I'll have to get all that out of there, correct? I'm going to have to get some kind of flexible brush or something.

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

So, this time used Gunk Engine Degreaser shot into the ports. Let soak 15 minutes, then used small sponges and forceps to break it up. Then I hit it with my pressure washer and fully 12 inches of black water came out before it ran clear. Also was johnny on the spot with my oiled up rag to oil the cylinder before rust set in. Turned out good. See picture!

 

[Yesterday]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

certainly won't hurt to be sure everything is cleaned out! You might as well start back out as close to new condition as you can, given the investment both in terms of dollars and time.

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Ah, bummer. Went to assemble my new .015 piston (insert rod, bearings, install rings) and found it's the wrong piston! Double checked my order from last year. Ordered the correct one, but received the wrong one. The tag wasn't on the box when I received it, but I didn't want to brake open the plastic seals on piston, pin, rings, etc. until I was ready to use it. It is for a Mercury, maybe a 135? I'll have to get a new one and figure out what this one is.

 

[marinermercury]

1985 Mariner 90 hp compression

1985 Mariner 90 hp compression

Hello, I am new to the site but have read a lot of you guys posts. I was hoping that one or more of you could help with some knowledge. I bought an 85 fish ski 17 ft with an 85 mariner 90hp six cylinder. On paddles it cranked and ran good. We took it out on water yesterday and it ran great. Planes out fast and sounds awesome. Well we only stayed out long enough to just see if it was a decent motor. While I was getting trailer, my son idled around just a few minutes in forward while I backed trailer in. Once he landed the boat he told me that it cut out on him a few times but he got it cranked again. After reading many posts from y'all I decided to go through the steps, compression test first. I checked and all six are reading right at 90 give or take 1. I read where many guys say the motor is worn out if below 100. Well I did the Decarb seafoam procedure on paddles and it actually sounded better once finished. I did the version where you have a gallon premix in small can mixed with full bottle of seafoam until all gone. I also sprayed a little in each carb while running. I thought about changing the plugs too but they look fine. My questions are,
Does low compression primarily affect idle and not so much mid and wot power?
What's likelihood of running motor couple seasons at the 90 psi without damaging anything else?
Is there any major parts stores that carry a comparable spark plug for this motor or do I need to just go to boat place or online?
Any help you guys can provide would be greatly appreciated. Thanks.

 

[marinermercury]

1985 Mariner 90 hp low compression

1985 Mariner 90 hp low compression

Hello, I am new to the site but have read a lot of you guys posts. I also posted this first as a quote somewhere, sorry i have never posted in forums. I was hoping that one or more of you could help with some knowledge. I bought an 85 fish ski 17 ft with an 85 mariner 90hp six cylinder. On paddles it cranked and ran good. We took it out on water yesterday and it ran great. Planes out fast and sounds awesome. Well we only stayed out long enough to just see if it was a decent motor. While I was getting trailer, my son idled around just a few minutes in forward while I backed trailer in. Once he landed the boat he told me that it cut out on him a few times but he got it cranked again. After reading many posts from y'all I decided to go through the steps, compression test first. I checked and all six are reading right at 90 give or take 1. I read where many guys say the motor is worn out if below 100. Well I did the Decarb seafoam procedure on paddles and it actually sounded better once finished. I did the version where you have a gallon premix in small can mixed with full bottle of seafoam until all gone. I also sprayed a little in each carb while running. Once done it actually sounded better.
Here are my questions.
It runs really good at 90psi, if I hold off on rebuild do I stand a chance of damaging any internals?
Is low compression a sure sign that I will always have idling problems in gear when really warmed up?
Is there a comparable spark plug that is available anywhere other than boat dealers and online?
50:1 or 40:1?

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

So, after a little research, I received one complete 0.015 piston (piston, rings, wrist pin, clips) for a Mercury 3.5" Loop Charge L3-L4 Part ? (OEM 821896A3?) (can anyone tell from the picture what brand??) and three standard ring sets also for a Mercury 3.5" Loop Charge L3-L4 Part 200-20 (OEM 39-822821A12).

I need an OEM piston 0.015 over 777-815965A5 and also three ring sets 96170A12.

Anybody want to trade? :lol:

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

I put the three ring sets on EBAY, auction starts tomorrow. Still trying to confirm for sure if the piston is 821896A3?

Now to get the RIGHT piston and ring sets!

 

[Faztbullet]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Those are WSM brand piston and rings which in my opinion are better than OEM (I sell a lot of these) and are correct for your motor if 3.5 bore

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Thanks for the feedback! That should help. Also, unfortunately it's not a 3.5 bore.

 

[Faztbullet]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

The shop charged me $30 to hone 3 cylinders and $45 to bore and hone the bad one. Total with tax $79.86! See before/after pics of the bad cylinder. They ended up boring it to 3.390 in or 0.015 oversize

Havent gotten the list on Email yet but yours is a small bore bottom guide piston engine.

huh

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

I could be wrong, this is my first rebuild. My engine serial number is 0D013888, 1991-2 115HP 4 Cyl. The specs from the manual and my measurements are:

 

[reynold460]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

I am currently rebuilding a 1989 115 hp merc serial number oc106992 I had a bad cylinder also bored out .015 and ordered piston merc number 9009a6 comes with rings my rods have number 638-8532-1 yours would be the same if you have same rods . I got new standard rings for other pistons on ebay cheap under 50 bucks also found seals etc cheap on ebay ,have not found the cause of my piston burning up yet but I suspect carb issues also since it was only cylinder good luck with your project I will be watchin to see how you make out and if I run into anything that may help you I will post it

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Good luck on your rebuild also! Rebuilding carbs is easy, I'll be interested hearing if the gunked up carbs did your engine in also.

I definitely have top guided pistons and rods, see manual and pics. I'll be ordering the correct piston and rings this week.

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Received my 0.015 piston kit today. It was loose in a box which was loose inside another box. :mad-new:

No apparent damage. I verified this time that it is the correct piston as soon as it arrived.

Rings for the other three pistons should arrive tomorrow and I can get back on the assembly track.:lol:

 

[reynold460]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

how ya makin out with your rebuild