What is the Difference Between an inline 6 115HP and 150HP?

[Merlin509]

Am looking at doing some work on my 1975 1150 inline 6, and am wondering what I can do to boost horsepower while I'm at it.

I'm wondering what the difference was between the 115hp and 150hp. Where the bore sizes different? Carbs? Compression (heads)?

Also, where is a good source for parts, including performance parts?

Any help would be greatly appreciated.

Thanks in advance.

 

[Faztbullet]

Re: What is the Difference Between an inline 6 115HP and 150HP?

I'm wondering what the difference was between the 115hp and 150hp.

Block and pistons are power ported on the 150 as are the internal passages on carbs and exhaust port timing is a little higher...

 

[Merlin509]

Re: What is the Difference Between an inline 6 115HP and 150HP?

Block and pistons are power ported on the 150 as are the internal passages on carbs and exhaust port timing is a little higher...

So, same bore and same heads? Any advantage to swapping with 150 carbs? Anything I can do to bump the power?

The deal is that this motor was dunked, so I'm cleaning it out and figured I'd step it up if I can.

Thanks again!

 

[jimmbo]

Re: What is the Difference Between an inline 6 115HP and 150HP?

Even though the displacement is the same, the Block, reed valves, carbs, exhaust tuners are different. Parts that might be different; cam follower on throttle linkage, pistons( some 115s, 1982 and later were power ported, but around 1984 a lower compression piston was used)

 

[j_martin]

Re: What is the Difference Between an inline 6 115HP and 150HP?

About 35 horsepower.

 

[mr 88]

Re: What is the Difference Between an inline 6 115HP and 150HP?

Last of the 150's was 1977 then the V6's 150's came out.Last of the 115's was 1988 and by that time they were very, very close in performance to the 150 Tower. Merc was pushing the V's and did not want to be in competition with itself and have two 150's in the lineup at the same time.So unless you have a 87-88 115 your out of luck with trying to turn it into a 150.Now you could buy new pistons,rings and gain in compression which would make it like new.There are some reeds available,[not boyeson from what I have read] that will add a tiny bit of oomph.Depending on your hull the best way to gain some hp would be to add a LWP and maybe a jackplate to get the lower unit out of the water.Less drag =more speed.
Adding larger carbs, or jets will not translate into more hp in stock form.The engine can only burn so much gas depending on the cylinder size etc.If all you had to do was add larger carbs on any engine to gain hp there would be a huge selection of them on every marine web site.

 

[Merlin509]

Re: What is the Difference Between an inline 6 115HP and 150HP?

About 35 horsepower.

Very funny.

Thanks to everyone for all the responses. Looks like I'll just have to put it on a smaller boat if I want to go faster.

 

[jimmbo]

Re: What is the Difference Between an inline 6 115HP and 150HP?

Very funny.

Thanks to everyone for all the responses. Looks like I'll just have to put it on a smaller boat if I want to go faster.

Proper setup; height, trim, propeller. Can make a pretty big difference. Getting rid of any unnecessary ballast(wife, kids) in the boat will help, girlfriends and Mistresses can stay

 

[Texasmark]

Re: What is the Difference Between an inline 6 115HP and 150HP?

Last of the 150's was 1977 then the V6's 150's came out.Last of the 115's was 1988 and by that time they were very, very close in performance to the 150 Tower.

I bought a 1989 17' Ranger Fisherman with a titled as 1989 115. Since you are not the first person that has mentioned the last production year for that engine was '88 one can only assume that it was built in '88 but made for '89 sales....like you can already buy a 2012 car but it's not 2012 yet.

Anyway they called it Direct Charged induction. It wasn't a looper, but it did have the ported piston, 2 rings per piston, high performance reed valves and all the other goodies and it was pretty gutsy. With a 24P prop on the first outing I hit 55 mph but the rpm's were low....don't remember the number. Dealer replaced it with a 19P as I recall (or 21) where by it spent it's life at 6000 rpm at WOT (still running today) and could pull me up on a slalom with a boat full of people.

My first vision of a 150 was a blue band as I recall, on a blue Hydrosport and the guy had just punched it out and was jumping my wake. The boat was clear out of the water and I could see his gearbox. She was singing like a meadowlark. In a flash he was out of sight.

Mark

 

[Merlin509]

Re: What is the Difference Between an inline 6 115HP and 150HP?

Proper setup; height, trim, propeller. Can make a pretty big difference. Getting rid of any unnecessary ballast(wife, kids) in the boat will help, girlfriends and Mistresses can stay

Assuming that I can get it in good running form again, I'll find a little 15' Allison or Hydrostream to throw it on with a jackplate, nose cone w/LWP and a good stainless prop and have some fun.

Mistresses and girlfriends tend to be lighter, so they don't slow it down very much. It's a scientific fact.