125 low power?

[danny9696]

Hi all I have an 89 1901 Bayliner with a force 125 on it, It usually runs about 35-38 with just me and a full tank of fuel @ about 4500rpm, thats the best I can get out of her, a friend of mine has a 97 force 120 on a 19' astro that weighs more than my boat, it flat runs, we swapped everything onto my boat just to try it out (not recommended, lots of work control...) but man did my boat run, almost 50mph @ 5400 rpm, I am running a 15 pitch prop and I can?t get over 4500rpm, we ran a 19 on the 120 and wow I was impressed, my compression is good @ 120psi on all cylinders, his was a bit higher at 125 but it would seem that I should be getting a little better, also with my 125 force I can run wide open down the lake and use 1/2 tank of fuel, the 120 used less than half of what I used, I rebuilt my carbs and re jetted them but it sure leaves a cloud behind it when running wide open

Can anyone give me any advice, maybe I am using the wrong plus? they seem way wet when I replace them,

Any help would be great

Thanks

Danny

 

[pnwboat]

Re: 125 low power?

I've played around with different jets on my 1988 125HP, but never could tell any difference. The standard jets gave the best overall performance.

The gear ratio on the lower unit in the 1997 is 2.07:1. On the 1989, it's 1.73:1. That's one reason why you can run a 19 pitch prop on the 97 at 5400 RPM's for more top end speed.

 

[Frank Acampora]

Re: 125 low power?

The 97 has Mercury lower unit and midleg, Mercury ignition, and different reeds. It is also a big bore-3.375 versus your 3.3125 125. I also think your engine has a closed hub prop while the 97 has thru-hub exhaust. These changes and the lower unit gear ratio make it a much stronger engine than yours. Nothing you can do about it short of massive modifications.

You can try swapping a 2 to 1 lower from a pre-1990 90 HP engine onto yours. That with a 17 pitch prop should give you about 3-5 MPH more.

 

[danny9696]

Re: 125 low power?

Thank you both for your help, I am going to try to talk him out of his engine, he wants more anyway and the 120 gives me just what I need for my fam! thank you again

Danny