Merc 25xs

[apache88]

Just picked up a 25xs Merc--short shaft--for my C stock hydro. The boat is a Giles. The transom height is 14 inches. My question is how high can I run the motor on the transom. The Merc is shorter than my Yamato 302. I don't race the boat, so I'm looking for a safe height to keep from starving the motor for water. Thanks.

[Aeroliner]

The water pickup for the engine is low. We run our 25XS with the prop shaft level with the bottom. Never had an issue.

Alan

[apache88]

Thanks for the reply. I think I have to cut the transom 2 inches to get close to the bullet being level with the bottom of the boat.

[zul8tr]

Thanks for the reply. I think I have to cut the transom 2 inches to get close to the bullet being level with the bottom of the boat.

As Alan states he runs the prop shaft level with the bottom. AS I understand his meaning that is not the same as the prop shaft center height at the bottom.

Consider cutting the transom to several 1/8" shims below your target height to allow for adjustment for different props and setup. Note that the prop shaft center is below the gear case front point of the casting (also true of the old Quicki A/B/C/D gear cases). So if you want the prop shaft center at the bottom that front point is above the bottom. See the pic of the 25xs in this link:

http://www.screamandfly.com/showthread.php?190317-Stock-outboard-racing

Even though you are not racing the boat in present APBA rules the 25SSH class hydros are limited to run the rear prop shaft center no higher than 1/2" below the bottom, but there is no rule restricting the angle of the prop shaft relative to the bottom. I would run the prop shaft level with the bottom and the rear center of the prop shaft no higher than 1/2" below the bottom as a safe location. You will determine by testing if you want to change the setting based on conditions, props, etc.

Be careful with this engine properly set up a hydro will run over 70 mph.

[champ20B]

As Alan states he runs the prop shaft level with the bottom. AS I understand his meaning that is not the same as the prop shaft center height at the bottom.

Consider cutting the transom to several 1/8" shims below your target height to allow for adjustment for different props and setup. Note that the prop shaft center is below the gear case front point of the casting (also true of the old Quicki A/B/C/D gear cases). So if you want the prop shaft center at the bottom that front point is above the bottom. See the pic of the 25xs in this link:

http://www.screamandfly.com/showthread.php?190317-Stock-outboard-racing

Even though you are not racing the boat in present APBA rules the 25SSH class hydros are limited to run the rear prop shaft center no higher than 1/2" below the bottom, but there is no rule restricting the angle of the prop shaft relative to the bottom. I would run the prop shaft level with the bottom and the rear center of the prop shaft no higher than 1/2" below the bottom as a safe location. You will determine by testing if you want to change the setting based on conditions, props, etc.

Be careful with this engine properly set up a hydro will run over 70 mph.

Exactly!!! Those 25XS mercs are quite fast I hear. The main thing is to NEVER RUN A FULLY EQUIPPED KNEELER RACE BOAT WITHOUT A SAFETY SPOTTER ON SHORE just in case something were to happen. Make sure you and your spotter agree on signals and he/she has a working cell-phone and binoculars. It is also good to bring a regular passenger boat along to have if needed.

[Aeroliner]

When I stated level to the bottom That puts the center down a little over 1/4 inch. We also run about 1/8 tuck on the engine to manage bow lift on our Montana Race Craft. Must also assume it has the correct later 25XS gear foot. The tall tower 25XS has the regular Quicksilver lower unit.

Alan

[zul8tr]

Exactly!!! Those 25XS mercs are quite fast I hear. The main thing is to NEVER RUN A FULLY EQUIPPED KNEELER RACE BOAT WITHOUT A SAFETY SPOTTER ON SHORE just in case something were to happen. Make sure you and your spotter agree on signals and he/she has a working cell-phone and binoculars. It is also good to bring a regular passenger boat along to have if needed.

"NEVER RUN A FULLY EQUIPPED KNEELER RACE BOAT WITHOUT A SAFETY SPOTTER ON SHORE". Goes for any race boat not just knee busters.

[BJuby]

"NEVER RUN A FULLY EQUIPPED KNEELER RACE BOAT WITHOUT A SAFETY SPOTTER ON SHORE". Goes for any race boat not just knee busters.

Totally agree. Got my first taste of a 25xs powered hydro on a fast rig last summer. Ran in the low 70s. What a ride! Dad ran it too, and since he weights 30lbs less than me was probably a little faster. It was the fastest he had been in a hydro. The owner of the rig was in his Jetski waiting on the shore to come assist if needed.

I have a line on a 25xs that I will be picking up in April, but may be in need of a used 25ssh/CSH hydro for it if the guy won't sell his.