Height of transom to waterline when resting in water

[ithica]

Hi there starmada friends . I have a 1974 or 1975 not sure , Starcraft holiday . I recently re powered with a new 2021 Yamaha f90 . Previously I had a 1969 mercury 80 hp. The weight of the old motor was 223 lbs . And the boat was rated back in the day for up to 125 hp which in 1975 with two stroke tech , the heaviest motor for a 125 was 265 lbs . The new motor I installed is 363 lbs . The transom is still good , it had been replaced once before and a pretty good resto was done on the boat about ten years ago . Now that I have the motor on and taken it out for some test runs , it runs great and planes beauty but now when I’m looking at it , it seems to sit low to the water at the back . As you guys know , the transom swoops down from the sides to a low point in the middle . In the middle I bet the water line is about two inches below the drain holes on the splash guard . What does everyone think the proper height from the transom top in the middle to the waterline should be when it’s at rest . ? When I reverse the water comes up over the transom
Onto the transom splash guard a bit if it’s turbulent . It’s been so long since I’ve driven it with the old motor I can’t remember if this was normal . Lol

 

[ithica]

Pardon me it’s an 18ft by the way

 

[mattsteg]

I've run boats (not starcraft) where you would get water in the splashwell if you went to the stern.

Is there a visible muck/waterline on your boat? These boats can sit low in back, if you add more weight they can sit lower, and if the flotation foam is saturated with water they can sit lower still.

Does the boat ride well? And is the transom very well sealed against water intrusion? You definitely want to avoid kicking off a rotting transom...

 

[ithica]

Hi and thanks for the reply! Yes it planes well , cruises really stable and you can’t move the motor at all or make the transom wiggle at all when applying pressure to the motor on the trailer . There’s no water coming in to the transom from
The wall at all . One soft spot for a Couple inches at the very bottom right inside where a fuel
Tank had rubbed and one small soft spot on the top left inside I think due to moisture from the stern light post but the main transom
Area all across is solid and firm
And all along the top of it is as well .

 

[roscoe]

I've had several Starcraft, Alumacraft, and Spectrum boats, that water came up to or into the splash well drain holes. You should be fine.

One of my current boats has a very shallow splash well (3-4" ) and it's only 11" front to back, so I must be careful to not back into a large swell or wave.

 

[ShoestringMariner]

Got pix?
My 16’ super sport has only had water come in the drain tubes at a super steep launch.

Under normal use, not even with a 65hp merc, an 8hp kicker, 3 cans of fuel and a battery in the back...plus waterlogged foam, 2 plys of rotten ply and my fat arse...in swells on Lake Huron....the tubes were high and dry.

Are the 18’ holiday tubs that much lower to the waterline than the SS’s?

 

[Watermann]

Holly's have a very light bow so that angle will add to your SW taking on water. I see no issue with what you're describing and that weight of 363 is nothing, my 18' Chief has an 800 lb cast iron V6 in the back albeit it's a full size IO transom.