Older mercury 115 rebuild

kuyote

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Mar 3, 2007
Messages
2
It looks like I bought a bad motor. When I took the plugs out, there was some aluminum around the hole. This I believe is a pretty common problem if run too lean. Should I rebuild it? Or get a new powerhead on ebay for $1400? How difficult is it to put on a new power head? I have never rebuilt marine motor's, but have plenty of experiance with auto's. The quote for a rebuild was a minimum of $1700. Thanks.
 

WillyBWright

Fleet Admiral
Joined
Dec 29, 2003
Messages
8,200
Re: Older mercury 115 rebuild

You can't overhaul it without special piston ring clamp tools. You have to clamp the rings and install all six pistons simultaneously with them already attached to the crankshaft. It's quite a feat, not for the squeamish or impatient. Have some extra rings handy. Most first-timers crack at least one.

Removing and reinstalling the powerhead is actually very easy. The hard part is synchronizing everything after you transfer all the parts to the new powerhead. Another task not for the squeamish. Do it wrong and bake another piston.

You would learn a lot about old Mercs in the process, including why they call them Black Anchors. ;)

You'll want to rebuild all three carbs and replace the whole water pump.

Check the compression. I've seen motors run for years with partially baked pistons. Maybe you'll get lucky and just need some carb rebuilds and a thorough sync & Link. I set max timing two degrees shy of spec to prevent detonated pistons in all of my tune-ups and overhauls on these. You'll never notice the <1mph loss of speed, and you need to to use today's alcohol blended gasoline.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,850
Re: Older mercury 115 rebuild

Willy is incorrect about having to use six piston ring compressors. It does make the job faster, but is not essential. I remove all pistons from the crank, collecting all the roller bearings and cap into six paper cups. Now oil and install each piston individually. I use fingers and a screwdriver to compress the rings. Now install the crankshaft. One by one pull the pistons up and using grease to hold the roller bearings and cages in place, install the bearings and cap.

The carbs are next to rebuild. They are pretty simple. The hardest part is the idle adjustment, but Clams posted an excellent link and sync method on these forums.
 

kuyote

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Mar 3, 2007
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2
Re: Older mercury 115 rebuild

OK, I think I will give it a try. If all else fails, I can get the powerhead on ebay.
 

Clams Canino

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Jan 10, 2004
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2,179
Re: Older mercury 115 rebuild

kuyote said:
OK, I think I will give it a try. If all else fails, I can get the powerhead on ebay.

OR, you could just contact me directly. :D

-W
 

OldMercsRule

Captain
Joined
Nov 30, 2006
Messages
3,340
Re: Older mercury 115 rebuild

Willy's right about the reputation of the old black motors I luv. My brother from Cordova Alaska is always trying to convince me to try to see if my motors will float, (known as: the float test), which generally verifies their significant value as great anchors, (drain all fluids first). But even though many think them anchors, (not me), if ya know their weakness: cooling, fuel systems, et al, and keep your eye on 'em, (knowing those weakness areas). pound for pound; dollar for dollar they have great power for the weight, and old water skiers, (like me), luv the no wake stump pullin' power for great skiing! Welcome to iboats! JR ps no reason to buy on ebay. If you are going to spend the $ for a rebuild might as well get from one of the very best: Clams, (the previous poster)
 

Scaaty

Vice Admiral
Joined
May 31, 2004
Messages
5,180
Re: Older mercury 115 rebuild

I'm putting together a little 16 foot Flatbottom SK type boat, and heres a pic of the totally rebuilt 135 going back together...go for it...best looking motors made

S5301518.jpg
 

OldMercsRule

Captain
Joined
Nov 30, 2006
Messages
3,340
Re: Older mercury 115 rebuild

Scaaty said:
I'm putting together a little 16 foot Flatbottom SK type boat, and heres a pic of the totally rebuilt 135 going back together...go for it...best looking motors made

S5301518.jpg

Lord that looks sweet n' clean n' all! Do you only work on your own stuff? JR ps not only are they the BEST lookin' but they do deliver lot's o' power/LB SCAATY!! JR
 

Scaaty

Vice Admiral
Joined
May 31, 2004
Messages
5,180
Re: Older mercury 115 rebuild

I usually do my own work, but I have a Merc friend that is a total wizard with Tower of Power Mercs. I have the short shaft case middle painted and back over there, and the PT+T ready. My motor will be a solid black wrap, newer style face plate...couple silver stripes for looks.. good looking now just sitting here in the shop!
On the motor, heres whats being done...
.."The powerhead I am building for you was originally a '72 1150.
The '72 1150 is a choked down 1350 with a few flow restrictions to give the lower HP rating so Merc wouldn't have to come up with a different powerhead to fill that HP range for the consumer market.
Initially this 1150 needed a rebuild because the inner water jacket had cracked and let water into #3 which was trying to die when I rescued the beast. It still had 95 psi on #3, but the rings had started to seize and consequently had scored the bore.
I had #3 bored .015 and installed a new piston there.
I had all holes pro-honed while I was at it and mic'd for roundness, etc to insure the beast was still within factory tolerences.
The block surfaces were machined too to insure everything was flat in the water jacket areas for a correct sealing.
All other pistons were carefully inspected, mic'd, & cleaned. I replaced one standard size piston too, but (4) of the (6) original pistons went back into their original holes.
Everybody got brand new rings & needle bearings.
The crankshaft got new main bearings.
The end caps got new seals & so did the crankcase.
I installed 1500 reed blocks and reeds, which meausre out the same as the original 1350 reeds.
I am installing '73 1400 carburetors - which are virtually identical to the original 1350 carbs & I am installing the original .0785main jets required for the 1350 at sea level
The exhaust tuner plate and inner water jacket are both NOS 1350 parts that I had machined to insure they too are flat so they will seal correctly.
These modifications: Main jets, reed blocks, tuner & inner wj complete the conversion of the 1150 to a true 1350.
The only difference between the 1350 and the 1400 blocks is the 1350 had an oval tuner to the mid-section and the 1400 had the dual square port tuner to the mid-section. And,...The inner wj & tuner plate configuration changed barely."

So when I can find somebody thats knows his stuff, its money well spent. Pick your friends well, and life is good. I'm in the process of getting wiring done on the boat, and couple months should get the hull wet. I'll do a post with pix in the Boat Building Forum when it comes together. Lots of work, but lots of fun too.
 

OldMercsRule

Captain
Joined
Nov 30, 2006
Messages
3,340
Re: Older mercury 115 rebuild

Hey SCAATY! Wow that was/is impressive. Just printed it to put in my favorite motor manual for safe keeping. I sure hope I get to meet you some time. If iboats has a left coast get together I will buy ya a beer or something just to soak up some of that knowlege. Maybe I could buy ya lunch sometime. I would luv to learn more. Thanks a lot! JR
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,446
Re: Older mercury 115 rebuild

I was wondering how you had a blue band 135 being that 71 was the last year for the 135 and the blue band cowl was introduced in 72. The 1400(non power ported) was only made in 72. In 73 the 1500 was introduced, so your carbs, if they were from a 140 must have been off of a 72.
 

Clams Canino

Commander
Joined
Jan 10, 2004
Messages
2,179
Re: Older mercury 115 rebuild

All the info above is correct on the 1150 to 1350 conversion. I'll add that you MIGHT get better (or safer) performance with the .080 main jets that all the other high output 99ci's used. Also make sure that max spark advance is get to no more than 21 degrees and that you run it on mid-grade gas only.

-W
 

Scaaty

Vice Admiral
Joined
May 31, 2004
Messages
5,180
Re: Older mercury 115 rebuild

He's well aware of the jetting and that I will be using cheap gas. And Jimbo, the wrap is sitting at my house. The wrap in the pic is for something else he building. This motor is a total "Frankenmerc" He has probably 10 motors just in that part of the shop, and 30-40 more in the garage...real eye candy. He's been building Tower of Power's for quite awhile...knows his stuff.
Yeah, an IBoats get together would be fun. Maybe we can hook up sometime anyway, if summer ever gets here! Got another pic sent yesterday of the motor...I'll post it in a second..(and just 10 feet from the block is a 1500XS like I used to have...just gorgeous! (not the one in the background in the pic..next time I go out there I take a pic of it)
PS. I'll forward the info on the .080 jets too, see what he says

RobbysFlattyproject22.jpg
 

Clams Canino

Commander
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Jan 10, 2004
Messages
2,179
Re: Older mercury 115 rebuild

What's always bothered me about the 1350 jetting is that the 1250 before it and the 1400 after it both used .082 as the default main jets. The later 1500 defaults to .080 Most experts advise against going smaller than .080 on a 1350 - especially with todays gas.

Merc was pretty reckless with the 1350 both in jetting it a bit lean, and setting tha max-advance to a whopping (reckless) 27 degrees. Within 2 years they learned and cut the advance back to a much safer 23 degrees.

Many, many, pistons melted in the early 70's due to detonation caused by the above combo of jets and timings.

-W
 

Scaaty

Vice Admiral
Joined
May 31, 2004
Messages
5,180
Re: Older mercury 115 rebuild

Melted a 1500 XS piston myself in the 70's. On the .080 jets and .0785, we will start on the 78ths and good gas for break in, see how it acts, do a plug chop or two, go to .080 if needed. Timings at 21. Thanks for the great info!
 

OldMercsRule

Captain
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Nov 30, 2006
Messages
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Re: Older mercury 115 rebuild

Aint it fun to be a fly on the wall when the BIG GUNS yak at each other? Great stuff!! JR
 

Clams Canino

Commander
Joined
Jan 10, 2004
Messages
2,179
Re: Older mercury 115 rebuild

Scaaty said:
Melted a 1500 XS piston myself in the 70's. On the .080 jets and .0785, we will start on the 78ths and good gas for break in, see how it acts, do a plug chop or two, go to .080 if needed. Timings at 21. Thanks for the great info!

Cool... just be carfull... one of the best ways to find out it's a little lean is to run it WOT and have a piston melt.
:(

-W
 

Scaaty

Vice Admiral
Joined
May 31, 2004
Messages
5,180
Re: Older mercury 115 rebuild

On the 1500XS I had, I melted a piston. Took it to my Merc Guru (lived back in Illinois then), and he tossed a new one in. Rest looked good. I get back out on the water, touch of break in, nailed it, and the beast just FLEW! Until it seemed like I had a bag plug. and the damn thing STILL ran like it did before I melted the first piston! Turns out I melted another one! He set me up for premium gas on timing, and I was running regular!!. Ah, the stupid and innocent days! Ran it back, new piston, then ran fine until I trashed the gearcase running a surfacing prop..heres a pic of what I'm building now. The motor parts are just the shell, and balanced there before painting. 15'9" Olsen Flatbottom, I weigh more than it does, trailer was free, but just got done making a new "roller" for it, back and rolling, in the shop, and doing whats needs to be done. I'll post a couple more pix in a second of my old Switzer, and the Flatty as it looks now..still fun to go broke building a fast boat!

S5301489.jpg
 
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