Pump jet and reverse bucket - bolts too long?

So I have just replaced the pump with one from PWC. I went to put the reverse bucket and all that back on, and I can’t tighten the bolts all the way in - stops about 1/4 or a bit more from the top. I believe the stock calls for M8x50 bolts. I’m nearly positive it needs shorter bolts based on some measurements I took with an Allen key inside there just for depth.

So two questions - is that the case? And two, why? Is the PWC unit not to manufacturer specs or have they decided for some reason not to include the correct size bolts or even guidance on that?

Pictures don’t want to attach