Late model Merc. I6 115 vs. Merc. 1500

[croSSed]

The later Merc. I6 115's were propshaft rated and had the same internal porting as the earlier (crankshaft rated) 1500 (150 crank h.p.). Has anyone out there dyno'd these two engines side by side? What is the REAL h.p. diff. between these to engines? I gotta know!!!! Thanks!

TG

 

[steelespike]

Re: Late model Merc. I6 115 vs. Merc. 1500

You might go over to Johns Old Mercury Web Site.
Excellent forum and great links.

 

[croSSed]

Re: Late model Merc. I6 115 vs. Merc. 1500

Thanks! I'll check it out.

TG

 

[ZmOz]

Re: Late model Merc. I6 115 vs. Merc. 1500

There is no difference. There were no mechanical changes when they started using 115hp stickers.

 

[croSSed]

Re: Late model Merc. I6 115 vs. Merc. 1500

There is no difference. There were no mechanical changes when they started using 115hp stickers.

Really??? Clams Camino told me that some where in the switch to the 140 h.p. (when Merc. intro'd the V-6 150) they used low dome pistons, to drop the compression I imagine. Then, when they went to the propshaft-rated 115 every other reed valve was reduced in size around the reed block. I would think that these two changes would result in a slight de-tuning. Is this wrong?

TG

 

[jimmbo]

Re: Late model Merc. I6 115 vs. Merc. 1500

I thought the low dome pistons were introduced in the 1984 models.

 

[croSSed]

Re: Late model Merc. I6 115 vs. Merc. 1500

I thought the low dome pistons were introduced in the 1984 models.

You're probably right; I never knew what year this happened. Isn't that also the year that they stopped producing the I6 140 and just had the 115, and it was propshaft rated?

TG

 

[croSSed]

Re: Late model Merc. I6 115 vs. Merc. 1500

I called my local Merc repair shop. The guy who owns the shop has been working on Mercs for MANY years, and he has a dyno. He had a book that showed how many pounds of pressure each engine should produce on a dyno - not h.p. per se, but comparative numbers nonetheless. According to Mercury's book the '87 115 produces 2200 lbs of force, whereas the later 140 produces 2350. Unless I am mistaken, the later 1400 was the exact same motor as the earlier 1500; they just put 140 stickers on it because they now offered a V-6 150. So, there is a difference; not much of one, but it's there.

TG

 

[phatmanmike]

Re: Late model Merc. I6 115 vs. Merc. 1500

same motors. no discernable diffrence

 

[jimmbo]

Re: Late model Merc. I6 115 vs. Merc. 1500

I called my local Merc repair shop. The guy who owns the shop has been working on Mercs for MANY years, and he has a dyno. He had a book that showed how many pounds of pressure each engine should produce on a dyno - not h.p. per se, but comparative numbers nonetheless. According to Mercury's book the '87 115 produces 2200 lbs of force, whereas the later 140 produces 2350. Unless I am mistaken, the later 1400 was the exact same motor as the earlier 1500; they just put 140 stickers on it because they now offered a V-6 150. So, there is a difference; not much of one, but it's there.

TG

I think you meant 77 not 87. 77 was the last year for the inline 150.

Merc prop rated the inline 6s in 1982.

 

[phatmanmike]

Re: Late model Merc. I6 115 vs. Merc. 1500

the late 70's inline 140s were 119hp at the prop.

the late 80s 115 inlines were also 119 at the prop.

the 140 became the 115 and the 115 became the 90

 

[croSSed]

Re: Late model Merc. I6 115 vs. Merc. 1500

the late 70's inline 140s were 119hp at the prop.

the late 80s 115 inlines were also 119 at the prop.

the 140 became the 115 and the 115 became the 90

Interesting! Thank you, Mike!

TG

 

[Texasmark]

Re: Late model Merc. I6 115 vs. Merc. 1500

Well I am a testimate to all that raw power cause I had an '89 tower and for a 115, that sucker was awesome.

When I first bought it the dealer had installed a Mercury 24P prop on it (don't remember which name but it was 3 blade, SS, and was ported). I had it on a Ranger 680 17' Console Fisherman which is deep V, lifting strakes, and padded (like their BB's but the rest of the hull was different; deeper).

I had to shut her down at 55mph cause of chine walk first time I had her out (and I couldn't see; eyes watering; and it scared me as I had never been that fast in a boat before). I replaced the 24 with a 21 of the same type and that's wherere I ran her.

With the ports in the prop she had an awesome hole (skiier popup) shot and after you were up and running real good, the holes would close and the rpm's would drop (under the load) and you would swear you had an automatic transmission (like in a car) and it had just settled down in overdrive.

I'd run trim out to the point where the speed would fall off. Rpm's were hard fast at 6000, she was just a singing and you could hear the prop's blades whacking the water.....made a humming noise distinctly different from the engine singing.

I loved to run that boat....son-in-law has it now.

Mark

 

[Clams Canino]

Re: Late model Merc. I6 115 vs. Merc. 1500

All close... no cigars.

When the V6 150 came out the inline 150 was stickered 1400 - no changes. However, VERY soon after the 1400 got the low-dome pistons to slightly reduce compression and avoid piston melt with the cheaper gas appearing.

In 1982 the ex-1400 went from 10 reeds per block to the 10/8 config with the even numbers getting only 8 reeds, this was called the propshaft rated 115.

So if you took a late 115 and put in 10/10 reed blocks and hi-dome pistons - you'd have an ADI 1500.

All that said.. in actual operation, they are virtually indistinguishable unless you are looking for the N'th degree of power.

-W

 

[Plainsman]

Re: Late model Merc. I6 115 vs. Merc. 1500

All close... no cigars.

When the V6 150 came out the inline 150 was stickered 1400 - no changes. However, VERY soon after the 1400 got the low-dome pistons to slightly reduce compression and avoid piston melt with the cheaper gas appearing.

In 1982 the ex-1400 went from 10 reeds per block to the 10/8 config with the even numbers getting only 8 reeds, this was called the propshaft rated 115.

So if you took a late 115 and put in 10/10 reed blocks and hi-dome pistons - you'd have an ADI 1500.

All that said.. in actual operation, they are virtually indistinguishable unless you are looking for the N'th degree of power.

-W

Glad to see your back!!! 8)