Upgrading to 90 Merc to 125 2+2 merc? Experience with the 125/115 2+2 mercs?

GreedyMuffin

GreedyMuffin

Petty Officer 3rd Class
Joined
Jul 1, 2016
Messages
97
Hi!

I got an Alicraft 18 Norwind.

Something is off and I only get 28 knots with 90HP, while others are reporting 33-35 with 90HP on the same hull. (It is a light hull, only 500KG).

I saw this great deal on a 2004/2005 Mercury 125HP 2+2 engine, two-stroke. I got the two-stroke classic as well.

With 28 knots, at 5400 WOT the engine is using around 38-39L, but on cruise (18-19 knots if I remember correctly) at 3500 it is only using 17-19L.

Would a 125HP at around 20 knots use more fuel at the same speed with a lower RPM?

Have anyone got any experience with these engines? My engine is stable at 7.5 bar on all cyls. Starts first try and is a solid engine!

Would it be a dumb choice to "re-power" with that engine? Fuel is around 1.63 USD pr liter, or 6.2 USD pr gallon of fuel here in Norway.

Thank you!

The 125 is cheap. Very, needs an service. I will test comp. and I can fire ut up. So I do not know the condition, but looks decent. I could perhaps make 500-600 USD from "upgrading".

Anyone know what sort of consumption at what RPM it is drinking? ex. at 5250 it is 50L, 4750 38L, 4250, 32L, 3750, 26L, 3000, 20L etc.
 
flyingscott

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
7,988
The 125 will use more fuel than a 90, more hp more fuel you may get a better cruising speed out of it. The 125 will be better on gas below 1800 rpm where it is running on 2 cylinders. I don't think there will be a big difference in fuel mileage but there will be a difference. I had a 125 2+2 motor I liked it very much. That being said they are quirky motors and one that needs service should be evaluated extra carefully. That is a motor that should be test driven before buying otherwise that $500-$600 you think you will make will be sucked up quick. The reason to test drive is to check the transition at 1800 rpms you can't just rev it in neutral.
 
GreedyMuffin

GreedyMuffin

Petty Officer 3rd Class
Joined
Jul 1, 2016
Messages
97
Hi!

Thank you!

Would it be needed to have it on water, or can you test on land, quick shifting it in gear?

The engine ran a little sour in the end of the season sad the owner. I am young (17), but I am not afraid to work on these two-strokes. They are simple, and I know the design very well if it is like the 90HP/75HP as I have read pages up and down before I got that engine.

The major thing to attract me is this: 35HP more for only 20KG, same or better fuel usage at the same speed. It is a few years newer.
 
flyingscott

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
7,988
The 125 is just your 3 cylinder with a 4 th piston added and that is where the similarities end. The 2+2 operation is controlled by the carbs the link and sync is tricky and must be done on the water. The bottom carbs have accelerator pumps in them you will need to buy the Factory manual it is the only one that will work for that motor. The 2+2 operation cannot be tested without being on the water or a test prop and tank. If the compression is good and you can keep your 90 hp for the time being until you know the 125 is running, and the motor is cheap. Also check for spark the 4 plugs always fire. I would take a chance but ultimately it is up to you.
 
GreedyMuffin

GreedyMuffin

Petty Officer 3rd Class
Joined
Jul 1, 2016
Messages
97
Hi!

Yeah, but the thing is that I can't test the engine in water I believe.

I can check for everything else though. Would you still take the chance?

He said that the enigne needs a new controll box as the trim-button does not work. I will take mine with it to test.

In Norway we only use the boat bewteen April-October. So the usage is low.

I can keep the 90HP for the time being yes. Will sell it later in the summer, worth more then.

So check-list.

? Check compression.
? Check gear oil
? Check trim/tilt
? Start the engine and see how it runs
? Check for spark

Is there anything else to do?

If I buy it, I will change plugs, impeller; thermostat, gear-oil, clean carbs.

Aka, full service!

The price is 17.000 NOK. I paid 19.000 for the 90HP newly served and checked from a dealer.

But in the summer I could probably get around 25.000 for my engine.
 
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