3.0 to 5.7 lt conversion (engine mounts)

[madbruno76]

Hi just replaced my blown up 3.0 lt mercrusier with a 5.7 mercuriser in a maxium sr 2004 has anyone got any info on what needs to be done to change the engine mounts. Cheers.

[mmwjr]

Wow that’s quite a change! The rear mounts in both cases are through the flywheel cover to inner transom plate. The front mounts are completely different between the two and are not interchangeable. You’ll need to use SBC front mounts and potentially modify the engine stringers to make them align.

[madbruno76]

Cheers mmwjr, the motor all ready is set up with SBC front mounts from the boat that it came out of, I was wondering if their was an out of the box solution for the front mount, I thought that the 350 was a stock option in the 2004 1800 sr, but can find no info or even mount pics to go by on the net.
Would be great to see how this motor was installed in a boat the same or similar build.
Is awesome that this forum exists fantastic resource and great to have people like yourself willing to share their experience.
Thankyou.

[shrew]

Originally Posted by madbruno76

I thought that the 350 was a stock option in the 2004 1800 sr, but can find no info or even mount pics to go by on the net.

A 350 in an 18 foot boat would be a lot of engine.

[mmwjr]

Not sure about the 350 being an option but the 4.3 was which is basically the same engine less 2 cylinders. Not sure how Maxum handled this but I know Bayliner had different stringer configurations for the 3.0 vs 4.3. So as I said you may need reconfigure them. Have you measured the distance between the 350’s front mounts and compared that to the stringer spacing?

[jparsons121]

Mercury published installation guides for all stern drives...
For example the 2004 3.0 has a single center mount where the 5.7 uses a side mounts.

Keep in mind you’re also adding approx 200lbs more weight to the stern than what the hull was designed for.

https://samerwebapp01apncus01.azuree..._2002-2004.pdf

https://samerwebapp01apncus01.azuree..._2002-2004.pdf

[madbruno76]

Cheers, Jparsons121 awesome thanks for the specs all sorted.