water in boat

[mario p]

hi guys this is my first post,having trouble with my sea nyphm its 17ft the one that the engine sits in a well in the boat,just changed outboards from a jhonston 25 horse two stroke,to a honda 15 horse four stroke,and gave it its first run yesterday problem is was taking in a lot of water at the back end when i tryed to gain power it was as if it was digging in everytime i tryed to give it throttle is this a problem any of you guys have knolledge of,is it the propeller?same size of longshaft any help or advice greatly apprieciated

 

[alldodge]

hi guys this is my first post,having trouble with my sea nyphm its 17ft the one that the engine sits in a well in the boat,just changed outboards from a jhonston 25 horse two stroke,to a honda 15 horse four stroke,and gave it its first run yesterday problem is was taking in a lot of water at the back end when i tryed to gain power it was as if it was digging in everytime i tryed to give it throttle is this a problem any of you guys have knolledge of,is it the propeller?same size of longshaft any help or advice greatly apprieciated

:welcome: to iboats

The leg may be tucked under the boat a bit to far, bring it out a bit farter from the transom.

 

[mario p]

tryed that made no difference?????

 

[Sea Rider]

Which size is you engine S, L, by taking lots of water, are you referring having water splashes out or intrusion over transom ? What's your transom height measured from middle transom to lower bottom/keel in straight line ?

Happy Boating

 

[steelespike]

If the motor is too short and in a "well" then it would be throwing water against the back of the well.
The boat probably needs a long shaft motor.
If the 25 was a healthy motor the 15 will struggle mightily to match the performance.

 

[Sea Rider]

If you are using a short/long shaft engine and having water splashes back or over trasnsom, need to raise engine a tad with wooden shims for water flow to skim right under small water deflector plate.



Water flow seems is hitting the (X) upper leg when should pass right under OK mark. Boat must be well trimmed and deck ballanced to ride parallel to sea level when on its way to play spot on with engine height.



Happy Boating

 

[steelespike]

He says the motor is in a "well" probably requires a long shaft.Would seem to me that it could be a short shaft and pushing water against the stern portion of the "well"throwing it over into the boat."taking in a lot of water at the backend when trying to gain more power".
I suppose it could simply be a 15" "well" and a long shaft motor simply splashing water over.But he actually seems to indicate it is"same size long shaft.
Perhaps he's wondering if the Honda is the same length long shaft

 

[Sea Rider]

All engines brands varies a bit its lower legs lengths among them, doesn't matter if are same S-L-XL sizes, some splash, others not. Having a well, the only possible way to check/solve that splash issue is with a pal riding a second boat parallel to Mario's boat. Spoter must face engine's side to have a good frontal visual to determine at which tail's height is water flow passing by at speed.

For me, the issue is Honda's small shaft length difference with water flow hitting the X mark as seen on previous posted pic. That's the only spot where water splashes out/over transom can be produced. To understand : there's a sharp edge right under small upper water deflector plate that extends to anticav plate, if water would be passing right under those plates would be perfectly cut there with no back splashes whatsoever. For the moment try height shimming the engine until water splashes disappears completely. Good luck.

Happy Boating

 

[Sea Rider]

Some data is missing :

To start with, what's the max HP rated for that size alum boat ?

Did the 25 HP previous engine plane the boat well ? the new 15 HP isn't.

Fast displacement speeds that doesn't achieve plane to overcome hull drag fast (raise hull out of water) will produce water flow to splashes against middle leg.

Seems a insufficient engine to plane such a large 17 footer.

Happy Boating