Whats the difference between a 125 & 150HP

[mrjeep]

I have an 89 Force 125 that needs rebuilding. I was wondering what the major changes between a 125 and 150 are. Is it a simple bigger bore,, does the 150 have a different crank, cam? Or are they two totally seperate creatures?
What can I do to get MORE POWER out of the 125 when I am rebuilding it?
Thanks, Nate

 

[Frank Acampora]

Re: Whats the difference between a 125 & 150HP

Aside from 25 ponies, the 125 is a 4 cylinder twin carb engine with a 2.875 stroke and 3.3125 bore. 150 is a 5 cylinder triple carb engine with a 2.80 stroke AND either a 3.3125 bore OR 3.375 bore depending upon year.

The 150 will usually beat the 125 hollow--"there aint no substitute for cubic inches" or "no replacement for displacement".

The 125 is difficult to get more power by modifying; I consider the 120 to be a better engine but: While you have it apart, you can square and enlarge the BYPASS ports to allow better airflow. Do not modify the exhaust ports. Since the #3 and #2 cylinders exhaust next to each other with a 30 degree timing overlap and into a common exhaust chamber, modifying exhaust ports will result in less power than stock.

You can try Boyeson reeds. Some people swear by them, some hate them. Me? I don't think much of them but I have not actually compared results on the same engine---yet.

You will gain a little speed out of the same engine by changing the lower unit to a 2 to 1 ratio gearpak and increase prop pitch by 2 inches.

 

[mrjeep]

Re: Whats the difference between a 125 & 150HP

WOW that was a lot of great info. Thanks I'll probably just go back with a stock rebuild then and look into changing the gearbox.
It's been my experience with Jeep engines that OEM factory stuff tends to last longer and be more dependable than high performance go fast stuff.

 

[kenmyfam]

Re: Whats the difference between a 125 & 150HP

WOW that was a lot of great info. Thanks I'll probably just go back with a stock rebuild then and look into changing the gearbox.
It's been my experience with Jeep engines that OEM factory stuff tends to last longer and be more dependable than high performance go fast stuff.

Is it worth the investment ?? or possibly better to find something else in good condition.
Just my 2 cents though.

 

[mrjeep]

Re: Whats the difference between a 125 & 150HP

Well I found a complete rebuild kit for under $600 or I can buy an old worn out unit that I have no idea of what I'm getting for about $2,000. Used outboard engines are ridiculusly expensive!!! You can go out and buy a complete boat,motor, and trailer for what they want for a used engine by itself.
I'll rebuild it!!!