Yamaha 15 mounted too high

[Sea Rider]

Some issues :

Doesn't matter if being a 2 or 4 stroke Yam motor both have tall gap plates, so ts is not an issue blaming one or the other.. For me that motor sits way high, can't tell how much the lower leg will drop when sitting the motor flush on transom, will guarantee that the combo will perfom much better in all water conditions from plain flat to choopy ones much better than if riding with a near exposed AV plate setting.

If sitting the motor flush on transom matches the nice prop/water performance as seen in pic 10 Bingo. Bad news, the wot rpm range factory stated for said motor is just 4500-5500, so at near 6 K the motor is being over revved by 500 rpm with current prop which is ? How loaded, number of souls were on board when the motor achieved 6 K ?

One big favor, when sitting the motor at 90 deg flush on transom, check if the wot rpm achieved were lower than before and by how much rpm if so.

Hez FB, I understand that you you're bored at home, but why do you want to unnecessarily confuse way more the OP with your post which it's all about recreational boating. If the motor hasn't been performing right as the OP expected while sitting way high surely to meet the BS dry motor installation about the AV plate facing the aft boat's bottom which everybody here loves going for, for what dark purpose do you want the OP to sit the motor much higher on transom to achieve or better what ?

Happy Boating​

 

[Hoppi84]

The motor is a 4 stroke. And its bolted to transom at 1 1/8" above transom so if I dropped it down it'd be deeper than pic. Full throttle operating range is 5-6k according to owners manual. And playing with the trim setting it was 5500-5600 all the way down and all way up was 5880-5900. That picture was all the way up.

 

[99yam40]

4 strokes are usually rated at a higher RPM than the 2 strokes is why I asked what the motor is
6K may be fine if it is a 4 stroke,

 

[Hoppi84]

F15SEHA 6AGK

 

[Hoppi84]

I was by myself but I have two batteries deck and bow mount trolling motor up front and the prop is 9.25x10.

 

[Faztbullet]

Fact ...The distance between the upper splash plate and AV have NOTHING to do with performance or mounting height. So give your BS on tall and short gap plates a rest. Below is straight from Yamaha manual........"motor to low increases drag and reduces efficiently". When you bury the prop/lower unit the drag is increased and prop is LESS efficient resulting in replacing it with a lower prop pitch to get RPM near spec. Manufacturers do not make boats that need the transom "butchered" so a motor can set deeper.