View Full Version : Mercury inline 6 interchangability?

08-20-2002, 07:43 AM

I've heard the bolt pattern is unique for my 1970 1350 however how unique is it? If I wanted to put a later model powerhead on it, what sort of changes would I need to do? I don't have a later model powerhead to compare with.

Thanks for any and all help!


08-20-2002, 09:48 AM
Totally different mid sections and powerheads. Just get a later model motor if that's what you want.

08-20-2002, 06:07 PM
Actually the bolt pattern is the same as the motors that preceeded the 135...the gasket pattern is different.

The difference between the later (140& higher and related 115's) and earlier bolt patterns is one stud on the exhaust side (and maybe the one behind it). The other 6 studs are the same place they've been since 1956. If you are willing to risk running with 7 studs and nuts you can bolt them up.........the gaskets will not correctly match.....but isn't that why they make RTV?

Jeff is right basically.....if the 135 gives up on you you are best off going for a whole late type 115, 140 or 150.

08-20-2002, 08:30 PM
Ew wee, I gotta add my 2 cents on that one. I've never tried sticking one on with two of the studs missing, because the exhaust isn't even close between the 71 and older stuff, and 72 1400 and everything else 73 and newer. The configuration is so different I don't think you could do it without major.......nevermind, it just won't work. The later mids are pretty plentiful and usually real cheap, even on E Bay, and the gearcases and cowl stuff all interchanges,

08-20-2002, 08:55 PM

This is what I was afraid of! Oh well, live and learn I guess. Now I have two odd balls! My 1100SS is unique and so is my 1350SS! Just for the record, how does it compare to the 1400? Is it basically the same without the powerport in the cylinder? My parts list shows it identical to the same year 1150 except for the reed stop settings and carb diffusers.

By the way, anyone ever put a small phillips screwdriver through their finger taking out the piston pin clips? Just before it slipped, the thought that this wasn't the smartest thing I've done went through my thick head.


Thanks again and good night!


08-21-2002, 09:07 AM
KIRK! No I haven't put a phillips screwdriver through my hand. Only slotted screwdrivers.

08-21-2002, 07:28 PM
In 70 & 71 the 1350's and 1150's were identical except for the carb diffusers and reed stops. In 72, the 1400 was the only engine in the line with the new bolt pattern in the bottom of the block. The 72 1150 still had the old bolt pattern and was still the same as the 70/71's. The 1400 was identical to the 73 and foward 1500 with the exception of the power ported pistons. When the new 1500 came out, the port timing was different from that of the 1150's for the same years and the reed stops and diffusers became the same for both engines. It would surprise me to learn that any 1150 after 71 had the port timing the same as the higher horsepower engine of the same year, although I've never been inside an 1150 after a 71 until a 75.

As far as the SS designation for the 1100, it distinguished it as having the new electronic ignition (SS = Solid State) This designation was not used on the 1350's. Many people now confuse the term with short shaft, but that's not what it was used for on the earlier engines. There were of course short and long shaft 1350's, just none designated SS.

stan merck
08-22-2002, 05:09 AM
2 other diff between 1350 and 1150, the ports on the 135's were as big as 150's , no power port though. the 1150 had much smaller and lower port timing. also the combustion chamber is tighter on a 1350 than any other in-line. a friend of mine discovered this when boring his. I cant remember how much diff it is but he said it was quite a bit.

08-22-2002, 07:12 AM
Stan, I've gotta disagree with you on that if you're referring to the same year model engines. The 1350 and 1150 powerheads were EXACTLY the same in 70 & 71 except for the reed stops and diffusers. The bare block is the same part number and Merc dealers regularly made the conversion from 1150's to 1350's back then. I believe that the 72 1150 shared this same configuration since it retained the old bolt pattern although the 1400 of that year had the new one. I think the 1150 changed port configuration in 73 when it got the new bolt pattern at the bottom, but again, I never got inside an 1150 again until a 75 model, but I'm pretty sure it took place in 73.

08-22-2002, 06:45 PM
Great stuff! Learning a bunch about my motor! My engine has a red decal on the wraparound, did Mercury change the color when the 1400 took over? I have the opportunity to pickup another spare block and was told it came from a red banded 1150. Since I have the oddball exhaust configuration, I figure it can't hurt to have a spare. Is there a way to machine the power port into the older blocks or is it just not worth it?

Thanks again!


08-22-2002, 07:57 PM
It can be done but I wouldn't bother. I have a 150 block that had porting added, basically a long slot. I haven't tried it yet. It was more common in the good ole days!

08-22-2002, 09:10 PM
Kirk, the 1400 had blue stickers as did all of the 72 motors. If the motor is truly a red stripe 1150 it would have the older bolt pattern and would be a suitable spare. If it was truly from a red motor, the powerhead would be silver and it'd have 2 fuel pumps on the side of the block. The silver block doesn't in itself define compatability. All 1500's and any other inline newer than 73 would be black though. Safest way is to look at the bolt pattern on the bottom.

08-22-2002, 09:38 PM

Thanks... Yeah, it has the two fuel pumps on the side and is the silver block. The price is right so if it has the odd bolt pattern, I'll pick it up. Kinda nice that Mercury used the same part for both motors and just made a couple little mods.

I seem to like the old stuff!


08-22-2002, 10:39 PM
Yes this all good stuff to learn since I have one of these old 1350 red line from 1970. No ss though.I am trying to pick some info on this engine and how to do things with it. It has been in storage for about 17 years and is very good shape. After taking the cover off I did notice that it looked very clean for being so old. It did have a new lower unit on it back in 85 with only 10 hours on it before storing it. I changed the oil and it did fire up ! Wow!
Any thing else I need to know about this engine would help. I did buy an mercury cd for the parts diagram and part numbers and a got a mercury book on it. So anything else that I need to know here.BEsides where to find parts!
Thanks to all,
I am glade I joined this forum!:D

Phillip Kastrup

08-23-2002, 06:58 AM
Kirk, the 135 bolt pattern isn't ODD, it is just the earlier pattern. There are probably as many with the same gasket pattern as the 135 as with the newer bolt and gasket pattern.

As for the bolt pattern remember it starts in 1956 with the Mark 75 and runs through the 135 in 1971; if either pattern is odd it is the 140/150 pattern.

08-23-2002, 08:04 AM
Hey who you calling odd Sam?

08-23-2002, 11:17 AM
does this mean the powerhead would bolt onto an earlier center section? How about interchangability of lower units? Will the later model lower units bolt onto the earlier center sections? I've also heard that it would be a good idea to get rid of the 1.78:1 ratio lower unit as this can lug the motor and cause the dreaded detonation problems.