Replacing Volvo 4.3GS (Volvo 290Duoprop) with Mercuriser 6.2- 350HP

Hello everyone,
I have Sealine S28 Bolero 1996 boat with two Volvo 4.3GS engines, Volvo 290 Duoprop sterndrives.I would like to replace the engines with Mercuriser 6.2L-350HP engines on my remaining sterndrives.What changes,modifications should I do? Is it possible or not?

Thanks everyone in advance )

More gearing in the outdrive.

Jeff

Ayuh,..... Not only will there be oodles of problems puttin' Mercs into Volvo engine beds, yer drives will need to be regeared as Jeff mentions,....

Fuel, electrical, exhaust, Everything will have to be re-engineered,....

Merc to Volvo beds not issue... V6 to V8 spacing from transom to engine support lag screws on stringers is the issue. Also as previously posted reduction for 8 and 6 cylinder engines different. Given hideous prices for parts from Volvo, you may be better off just changing the lower 1/3 of the drive legs... all "reduction" gearing takes place there. Gearing in top 1/3 is just fwd/n/rev. Lower 1/3 often avail used.... AND.... I discovered that the exhaust porting thru the transom and lower unit on 200 series Volvo drives is too small for V8s. Merc specifies (for 5.7 for example) that the exhaust port, if a single needs to be 4" dia, 3" if duals. The equivalent diameter on later 200s is less than 2 1/2". I changed my thru drive exhaust to thru transom (with dual 3"centek shorty mufflers) I got another 450 RPM at WOT. Even if you stay with thru drive, exhaust routing will be a challenge.

You have a 1996 boat with Volvo Penta AQ290 drives?

Pardon my language, and don't take it personally, but there's not much to be gained by repowering a great fat whale of an express with bigger engines. You MIGHT get a couple knots of high end out of it. You'd still be pushing the same hull, same weight (ugh), with the same old drives and propellers. If you have visions of skittering across the wave tops like a Pete Fountain racer, well, um, no.
These bloated luxo-pads are designed for entertaining, weekending, and generally behaving like a water borne RV. Am I being harsh? Probably.
If it were me, and I was looking at the 40,000 quid for just the parts (no idea on installation costs over there) I would start looking around for a faster boat that was more in keeping with my needs.