Corroded Exhaust Plate

[captaintony3]

2B018118
2013 200hp Optimax 25”
1300 hours

I have upper motor mounts on my exhaust adapter plate that have corroded and bad rubber. I removed the exhaust adapter plate together with the exhaust tube from the driveshaft housing so I may inspect both sides of each part and found that my bolts are corroded and cemented in place. Three of the bolts snapped off. A friend is removing the remains of the bolts from the plate. At least the exhaust adapter plate is separate from the exhaust tube. The problem with the exhaust adapter plate is that there is corrosion where the idle exhaust boot hose couples up to it and does not seal properly.

Can I have a welder put an aluminum plate and cut out an opening where the exhaust boot hose couples up to it? If so, what kind of weld should be used? Also, I want to have the surfaces of the exhaust plate and exhaust tube milled at a machine shop for the new gaskets for a perfect fit. Looks like the surfaces had black Mercury paint on them. Should I also paint after milling? Once I know I can put in my order for parts to Ms Rhonda and get my BBC discount. A new exhaust adapter plate is about $900+ and I am trying to keep cost down.
exhaust plate.jpg

[EuropeanAM]

Replace that plate. Not even a question in this case.

[captaintony3]

Will do. Thanks.

[captaintony3]

Ordered my new parts thru Rhonda. I have cleaned up the exhaust tube and exhaust housing areas. Had some corrosion and sanded them to clean aluminum. Should I prime and paint the bare metal where the new gasket will join the exhaust tube to the exhaust plate? Also, should I prime and paint the bottom of the engine block where the new gasket joins the exhaust plate?

[lpugh]

Ordered my new parts thru Rhonda. I have cleaned up the exhaust tube and exhaust housing areas. Had some corrosion and sanded them to clean aluminum. Should I prime and paint the bare metal where the new gasket will join the exhaust tube to the exhaust plate? Also, should I prime and paint the bottom of the engine block where the new gasket joins the exhaust plate?

No, but pull those studs for proper cleaning, do no use any power or rotary tools to do this as they will destroy that flat surface

[captaintony3]

Do I use the two nut method on the stud with heat and penetrating oil (I use Kroil)? I have not removed anything on the powerhead. Should I?

[EuropeanAM]

Do I use the two nut method on the stud with heat and penetrating oil (I use Kroil)? I have not removed anything on the powerhead. Should I?

Yes on Two-nuts and Kroil. Heat only if necessary, and recommend only a heat gun.

DON'T SAND ON SURFACES- EVEN A VERY SLIGHT DISTORTION FROM DOING SO WILL CAUSE SIGNIFICANT LEAKAGE!