Which is better: 1988 Mercury 100 HP or 1991 Mercury 115 HP?

[eduventure]

I am looking into purchasing a boat for the first time and am looking at two 16 foot Starcraft Medalist boats. One has a 1988 100 HP outboard and the other has a 1991 115 HP outboard. I was told that the 115 HP would go through fuel more quickly than the 100 HP. Is this true? I understand that it depends on many factors, but want to know if there is a big difference in the efficiency of the motors. I would appreciate any help in this area. I am planning to use the boat on small lakes for skiing and tubing.

Thank you,
Shawn

[faztbullet]

These are the same exact motors and the only difference is the carbs, the 115hp will use less fuel at as the 100hp will work harder at the same speed.

[eduventure]

Thank you for answering my question so quickly!

[Frige]

I know really old thread sorry. But I have a 1988 merc 100. I have had some people say that changing the carbs will make it 115 hp. Then some say no I will just waste my money and it will flood out. Ideas?

[Texasmark]

I bought a new Ranger bass boat with a 115 HP 6 cylinder "Tower of Power" in 1989...on the title listed as a 1989 engine. Folks in the know on here said that Merc. did the change over in 1988.......sooooo I guess I had an engine built in '88 and marketed in '89, not an unusual process. The engine was "Direct Charged" and was Merc's intermediate solution to the OMC Loopers which were known for their fuel economy over their previous "cross flow" conventional scavenging engines....which loved to stop by the gas station....BTDT

Out comes the new Loop Charged Mercs in 1989, 3 and 4 cylinder, 60 HP Jet 3 cyl to 125 HP 4 cyl. Later on I bought a 115 hp one of these engines. I remember the '89 was very fuel efficient as is the current 2002 115. I can't recall that fuel was an issue worth mentioning with either. Do I have a preference? Well, it's hard to beat a 2 stroke 6 cylinder engine of any type for smoothness of idle.....like a well oiled Singer Sewing Machine. But the current 4 cylinder, which runs on 2 cylinders at low speeds is very smooth....as long as you tilt the back of the engine up 10-15*. Otherwise it wiggles a bit.

To answer your question, I'd say noise would be the big difference as the newer engines had a foam insulated one piece, plastic cover, very effective noise canceller, where as the inline 6 had a wrap around cowl with a plastic bag of loose fiberglass for sound deadening. Course when it was making the most noise, it was going the fastest, which it did very well and most of the sound was way behind the boat.

Also the lower unit was beefier, I don't recall the '89 being thermostatically controlled, and the improved trim setup did a better job of allowing the engine to raise up when hitting an obstruction, reducing damage to the LU.....the trim ram was separate and just pushed up against the mid section rather than being a single cylinder for trim and tilt, locking the midsection to the hydraulic pressure of the TT unit at the time of impact.....as I recall on the '89. I recall an earlier Merc 850 I had with the same trim and one day I ran over a concrete anchor to a marina. Rear of the boat raised and fell as I passed over it.....don't recall any noticeable movement of the engine. Upon loading the boat on the trailer to go home, I noticed that the lower part of the skeg was missing...just sheared right off.

[racerone]

The ---" direct charge " ----Is not much different than ---" crossflow " ----as far as scavenging the cylinder.-----Marketing 101 says that most folks have no clue on internal working of a 2 stroke.----You can fool them with this terminology.

[faztbullet]

The 1988-1993 are all small bore 105 CID motors and the 1994 and up are big bore 113 CID motors. If you can find a set off a pre 1993 motor it will work...

[Texasmark]

The 1988-1993 are all small bore 105 CID motors and the 1994 and up are big bore 113 CID motors. If you can find a set off a pre 1993 motor it will work...

Interesting. Being of a curious nature, what else was different in the engines for a given HP....RPM max rating changed? Carb jets? Reeds? Porting? I guess, like their 2k vs 2.5k Bass boat V engines, better hole shot with more cubes?

[Frige]

I found a set of 115 hp carbs but I dont know the year. There is a number on the carb 3301-9012

[XS POWER]

When it comes to part numbers i just punch them into my search bar and it usually tells me what i need to know hope this helps good luck