Force 125 vs Merc 115

[Glenn Iverson]

I have a 1989 Force 125 single exhaust with the 1.73:1 lower end. Just curious how this motor would compare to one of the later Merc 115 6 cylinder "tower of power" motors assuming that both are running well.Which would have the better top end ? Which would be thirstier on fuel? And lastly which one is harder to work on?

 

[flyingscott]

The force will be better on gas and easier to work on. The merc will be faster

 

[jerryjerry05]

"Faster"
​Put on the same boat, with the motor at peak operating.
The right prop and the motors running the recommended the rpm's.
The 125 has 10 more horses.
That would be the faster one.

These 125hp Forces were rated at the time.
"The best power to weight ratio on the market"

Now remember it's only 125hp and your not gonna set speed records.

Actually a 83/4 85hp Force set a speed record.
On a 12ft.hydroplane and a jack plate it went 83 mph.

 

[jimmbo]

How late of a merc? 1981? 1982? 1986?
The force, having more displacement should have better acceleration. The merc will have better exhaust tuning and will be better on gas, the exhaust tuning might put it on par for acceleration. Top speed will be close, probably within 1 mph.

 

[Glenn Iverson]

The Merc is a 1988 or 89. A guy has one for sale with power trim & cables. Says compression is great on all 6 & services every year.He bought a 4 stroke.My 89 force runs well but I think it's on borrowed time before a rebuild is in order. For the price if the motor is as good as he says if a swap would make sense. My boat is a 19.7 Arriva bowrider.

 

[Keith Ogden]

No Title

I love my Force 125 ! she is old but starts up every season (4 now) and have dropped no money other then replacing the fuel screen .
https://youtu.be/-HCgrDutpE8

 

[SkiDad]

i grew up on a tower of power - it was pretty fast on top end but didn't pull as hard out of the hole for slalom skiers. We tried several props. This was a 1973 model though so they might have fixed that torque issue later down the line.

Still love that sound of that old Merc. I don't think they would be anywhere as easy to for on as the Force though - we have 2 of them and easy as pie. As for starting - ours has always started very easy when cold - something that Merc wasn't always famous for.

 

[jerryjerry05]

Not an expert but have heard the reason they stopped the "tower" was the problems with the exhaust and not getting fuel to the top cylinders.
​Same reason they stopped the 150hp 5cyl. inline Force.

IF??? your compression is good and you maintain it properly??
That motor can last a lot longer than your thinking!.

Little things like a de-carb, cleaning the fuel recirc system, adding a filter between the carb and pump can increase the life span significantly!

My twins are 1988 and the compression is as good today as when it was new.

 

[jimmbo]

I believe 86 or 87 was the last yr for the inline 6. You say your Force runs well, but... The owner of the merc says it's in great shape and runs well... The Merc is as old or older as your engine. If the merc is a real great deal. buy it, prepare it for a long nap, and use you force till it quits, then swap.

 

[jimmbo]

i grew up on a tower of power - it was pretty fast on top end but didn't pull as hard out of the hole for slalom skiers. We tried several props. This was a 1973 model though so they might have fixed that torque issue later down the line.

Still love that sound of that old Merc. I don't think they would be anywhere as easy to for on as the Force though - we have 2 of them and easy as pie. As for starting - ours has always started very easy when cold - something that Merc wasn't always famous for.

Which 'tower of power' did you have? The 150? It made great power between 4000 - 6000 rpm, but from 2000 - 4000, it wasn't the smoothest or a torque monster. The 90hp from the late 70s til 86 had low end pull to spare. Heck my 1984 115 pulled barefooters out of the water without skies

 

[Glenn Iverson]

I believe 86 or 87 was the last yr for the inline 6. You say your Force runs well, but... The owner of the merc says it's in great shape and runs well... The Merc is as old or older as your engine. If the merc is a real great deal. buy it, prepare it for a long nap, and use you force till it quits, then swap.

My mistake that Merc is an 83 model. Yes my Force runs well, that was my plan to have a backup motor to put to sleep until that time comes. Force parts are starting to get scarce & copycat parts from the Orient are crap.For the time being I think I will leave well enough alone.