Mercury v-225

[Btaggart]

I have 1980 mercury V-225 3.0l. Have had many issues with it. My issue I'm currently working with is that when I back in and submerge the the motor, it will not run if I lower it all the way down. I have to leave the motor titled upwards. I'm thinking motor may be setting to low on the factory plate causing to much back pressure through the exhaust system. Any opinions would be helpful

 

[faztbullet]

Merc did not make a 3.0L in 1980...either a 2.4L or a old 3.4L.....