Covert 115hp to 150hp

[Time2fish]

Ok, here is what I am thinking and hopefully some of you wiser gents than me can help.
What I presently have is a 1977 blue band Merc 1150 and my question is as you can tell by my post, what would it entitle to convert this motor over to a 1500.
I have a blown 1978 1500 and from what I can remember from other posts is that both blocks are pretty much the same, 99 cu in motors.
What or if I can even do this would I have to scavange from the other motor. I know the carbs, exhaust ports make it differenet, I had already took the distribitor off and rebuilt it last year and have it now on my motor.
I know Clams doesnt visit here anymore but pretty sure Laddies or some more knowledge people could answer some of these questions.
My 115 is a great motor, good compression across all cylinders, not sure even if I will do this maybe more than anything curious in case I get the winter blues.
Thanks, Rob8)

 

[jimmbo]

Re: Covert 115hp to 150hp

The blocks, pistons, reed valve assemblies, carburators, and exhaust tuners are different.

BTW a 1978 150 is a V6, 1977 was the last year for the inline 150.

 

[Time2fish]

Re: Covert 115hp to 150hp

I do stand corrected, the 1500 is in fact a 1976 model.
Looking at the motor it is the same as my 1977 1150, I know both of these motors as well as the 135 and 140 are all 99 cu in blocks, inline 6.
Thanks and sorry about that,
Rob

 

[Chris1956]

Re: Covert 115hp to 150hp

Time, The blocks are the most different. Can you reuse the 1500 block? The pistons differ by a power port on the intake skirt, and you can buy these. The carbs will swap. The reeds will likely swap. Ignition is identical

 

[Time2fish]

Re: Covert 115hp to 150hp

Thanks Chris,
Not sure about the block on the 150 if its worth salvaging or not. I guess you answered another question for me though, my block is not the same as the 150 even though cu in are pretty much the same or are you just talking about the skirting on the pistons?

 

[jimmbo]

Re: Covert 115hp to 150hp

The pistons have the 1 inch port(hole) on the intake side of the skirt, which matches up to an additional transfer path in the 150 block. This allows slightly more air/fuel into the cylinder.

 

[Time2fish]

Re: Covert 115hp to 150hp

OK, I understand
Seems to me that should salvage all the electrical parts of this motor and then R.I.P
The old 1500 is really not worth salvaging but that actually was not my original intent with this post. I was just curious if I could have used my 115 block without getting into it too much ($) and coming out on the other side with a 150 hp. I am quite fine with my 1150 just curious.
Thanks,

 

[Texasmark]

Re: Covert 115hp to 150hp

The port you mention is the "Direct Charge" port; Merc's answer to OMC's Loop charging prior to their patent running out. Don't know what else DC may have done, but mine had super fuel economy and ran like a sewing machine.

Mark

 

[Bob_VT]

Re: Covert 115hp to 150hp

Okay.... this is direct from Clams (who is one of the best on the subject) All about 99cu inch.....

1968/1969 Merc 1250 (125hp) Is a critter unto itself and only interchangable with a '68 or '69 1250.

In 1970 the new "direct charge" powerhead came out. The 1970,1971 Merc 1350 (135hp) as well as the 1970, 1971, and 1972 Merc 1150 (115hp) all used this new powerhead. Also I can convert those early 115's to 135's for a small additional fee. This cannot be done with the 1972 and up powerheads.

The 1972 1400 (140 hp) marks the beginning of the "new" exhaust ports and base gasket / bolt pattern. This pattern lasted to the end of the inline six. In 1973 the 115 also got the new bolt pattern. This means that (with the exception of the 1972 115 that interchanges with '70 and '71) all the distributor ignition inline six powerheads made from 1972 to late 1979 will bolt on interchange. Also, this means that you can bolt a 140 or 150 onto a 115 leg to upgrade your outboard - the only difference in the powerhead is the internal porting. You cannot convert these 115's to 140/150 hp version, the internal porting is radicly different. But you can bolt a 150/140 powerhead to the 115 leg with no problem at all, the lower units are all the same. Also the 1972 140 is a "true 140". But, the later 70's 140's are identical to the 150's. Once Mercury came out with the V-6 150 in the mid-70's, the marketing guys renamed the 1500 inline to a 1400 so as to not have two 150's competing against each other.

Lastly, In late 1979 mercury did away with the distributor ignition and went with the modern ADI ignition. In 1982 they re-rated the powerheads to "propshaft HP" as opposed to earlier "crankshaft HP". The old 115 was called a "90" and the 140 became the "115". All the ADI ignition powerheads will interchange.

 

[jimmbo]

Re: Covert 115hp to 150hp

The port you mention is the "Direct Charge" port; Merc's answer to OMC's Loop charging prior to their patent running out. Don't know what else DC may have done, but mine had super fuel economy and ran like a sewing machine.

Mark

Actually the port or hole in the piston skirt is not the "Direct Charge Port". It is the "Power Port" of Power Ported Pistons.
Direct Charge is a variation of crossflow charging. The deflector on the piston has a different shape when compared to other crossflow pistons.
Power ported pistons, in addition to the 1 inch hole in the skirt, have a beveled edge at the top of the piston directly above the power port. The port, the beveled edge, and a recess in the lower cylinder wall combine to
create a new and third intake port. this extra port, combines with the two regular ports all direct charge engines have

 

[Texasmark]

Re: Covert 115hp to 150hp

Yeah, that's what I said jimmo 8) . I don't know. :% I just know I saw the hole (know it wasn't in there before) and saw their pictures in their sales literature and read their sales pitches about this great thing and all. I had the '89 115 but never had to pull the pistons...think I had it 7 years and only replaced the water jacket gasket over the pistons once. I did look at the crown of the pistons when changing plugs (once) and thought it was like the crossflow (observed that it wasn't flat like loopers), but not having a crossflow there to compare just made it a (looks like) ill conceived (looks like) assumption.

I do know this, however. I had a 10 gallon tank in a 17' Ranger Fisherman and I didn't always fill it before a trip and never ran out of fuel. Don't remember the performance numbers, but it was fast, considering it only 115 hp on a heavy (padded however) boat and I liked to pull up along side other boats (in my hp range of course) and try to coax them into a little sport.

Mark

 

[Time2fish]

Re: Covert 115hp to 150hp

Thanks guys,
I knew I had read that post long ago from Clams but just could not remember where to look.
My question has been answered though, I do love my 115 but as I noted earlier, was just interested. There is a world of wealth on this site thats why I always look here first if I ever need any questions answered.
Thanks,

 

[timmathis]

Re: Covert 115hp to 150hp

What has happend to clams? You said he does not visit here anymore? What is the deal? Tim

 

[gungalunge]

Re: Covert 115hp to 150hp

if this helps in your idea to torque up a mercury 115 to a running machine . I set out on the same quest . and did it . asking all of our techs out her ,for lots of advise . I DID DUMB THINGS .. I started out last year. by late july i was on the water . rebuilt the engine . all of it . a week at a time . I tried to max mine out , And did it . I cannot say i got 150 hp out of it . but man does it run , I bored the engine block wiesco pistons . and new reed valves .it fires right up .proud of that . i set the timming .clams helped me there .. the carbs on this engine need .help not consistant ..someone out there give us good a mod to make this motor . right .. PLEase .