2015 721 with 20024 Merc 4Stroke falls off pad

[Tjflickshake]

I have a 2015 721 that had a 2 stroke Merc 250 that ran awesome, thought I would repower with a new engine for warranty purposes. This issue never happened with the 2 stroke on it. So I just got the New 250 pro XS 4stroke out of the 2hr break in and wanted to see where it was at. Oh it also has 10in h atlas and 24 Croxton B&B worked Fury on it as well jackplate was all the way down and never lifted. When I trim it out and gets to about 5700 at 67-68 the rear end kicks out. The original engine never did that it would run 70+ and smooth as silk the only thing that has changed is the new engine. Has anyone experienced this

[ThomasD]

Gearcase design is different between the 2 stroke opti and new 4 strokes.

[Tjflickshake]

So what’s that mean

[bassfisher444]

Where you running a 24 Fury on your 2 stroke and was the motor at the same height? Generally when switching to a 4 stroke you need to drop 1 or 2" of pitch and possibly lower the motor some.

[Tjflickshake]

It’s on a hydraulic plate that was all the way down

[bassfisher444]

It’s on a hydraulic plate that was all the way down

So you have tried adjusting it some then? What is your prop to pad with it all the way down?

[BassDaggett]

It’s on a hydraulic plate that was all the way down

If you are running 60+ with the HJP all the way down that is a problem waiting to happen IMHO. I've had a 721 (SHO then ProXS) and currently have a 921(4XS). Somewhere between 10-14 on an Atlas HJP was the sweet spot depending on prop. If I had ran either one of them all the way down, 0 or 1, in the 60s and started trimming up it would have been a squirllly ride!!!

[Tjflickshake]

So you are saying raise the plate up. The only reason I didn’t raise it is bc I just got out of the two hrs of break in and I don’t have the water pressure sensor yet for my smartcraft gauge to tell me pressure so I left it down. It never did it with my 2stroke Pro xs but I also never ran that motor with the plate all the way down trimmed out before either

[BassDaggett]

So you are saying raise the plate up. The only reason I didn’t raise it is bc I just got out of the two hrs of break in and I don’t have the water pressure sensor yet for my smartcraft gauge to tell me pressure so I left it down. It never did it with my 2stroke Pro xs but I also never ran that motor with the plate all the way down trimmed out before either

I would start the HJP (Assuming it’s an Atlas) at 10 and see how it performs. When I went to all Lithium batteries recently I’ve noticed the stern runs higher and lowering seems to help speed. From there you could go up to 12 or down to 8 and see what works best. If you have lead batteries I would only go up to 12 or 14. Hope that helps. I’d be REALLY surprised if you have any water pressure concerns running between 8-14 regardless of battery type unless you are running the trim really high (which Phoenix hulls typically don’t like IMHO).