1985 Mercury 18xd

[kingsnakejr]

Have a 1985 merc 18xd and repair manual. All specifications for 18xd and 25xd are identical (stroke,bore,displacement,etc are exactly the same. The only differences are the rpm range for the 25xd is about 500 rpm higher than the 18xd and the high speed jet size for the 25xd is .080 and the 18xd is .057. Will changing the .057 jet for a .080 jet result in 25 hp?

 

[JB]

Re: 1985 Mercury 18xd

No. It would result in a lousy running 18.

There are differences that are not listed in the specs.

 

[Laddies]

Re: 1985 Mercury 18xd

The main differance in the 2 engines is in the tuning pipe which is NLA

 

[kingsnakejr]

Re: 1985 Mercury 18xd

Thanks fellas,
Glad I didn't waste my time and money. Seems a shame that I can't get 7 more HP out two almost identical engines.
Thanks anyway.

 

[rvbilly]

Re: 1985 Mercury 18xd

I have a 18XD also , if you can find a 25 Hp exhaust tuner it will work !!

 

[nelsonag]

Re: 1985 Mercury 18xd

I have a 18XD also , if you can find a 25 Hp exhaust tuner it will work !

Re: 1985 Mercury 18xd

The main differance in the 2 engines is in the tuning pipe which is NLA

I just did this! there is no difference between the 18, 20, and 25 aside from the carb, and the tuner. I replaced the carb with a 25hp model, did not touch the tuner, I cant say how much the 18hp tuner is holding it back but it was well worth the upgrade in power for a $150 carb upgrade.