Merc 450R - rigging

Toffen Gunnufsen

Active Member
Oct 10, 2016
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I hope you all are well.

I will buy a 450R in near future. It will replace my Verado 400R on my Phantom 25.

If I am correct this set up is not a plug and play as fx Verado 350 Sci to 400R.

Do I need to buy a wire harness, different fuel line and steering set up? Anything more?

Can I use something from my 400R setup with the new motor?

If I am correct the upgraded steering for 450R has a higher psi. Is the upgraded steering more precise than the standard Verado power steering? My steering cylinder below the helm has a little slack. Its been replaced with a new and the issue still is there. My reason for asking is that a 100% precise steering is a must driving close to 100 mph.

Thanks for your help !

Cheeers, Toffen


Bullhead bully

Well-Known Member
Oct 26, 2014
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Hello, you are correct there will be some changes that need to be done. The rigging that you have for the 400 will need to be changed a bit. If I am correct the wire harness will need to be pulled back in to the boat you’ll need to install a rigging center box in the aft transom area , the 450 comes with its own pigtail that will plug into that. All your fuel lines will need to be changed to half inch diameter. 3/8 is not big enough for the 450. And you will also need to go to the higher psI 450 mercury steering. Stick with the matched set up that they have. I know there’s aftermarket steering I would just stick with what’s proven and warranty for the motor which is all mercury stuff.

Also the engine mounting needs to be rated for the 450 With 9/16 diameter bolts. Even though the weight is almost the same the torque the engine puts out will put extra stress on whatever mount you have. If you’re bolted directly to the boat you should be good.

There’s a few people that check on The church that are more versed with that. I know one or two of them I will send a message to them and ask them to chime in.

Have fun with the update. The 450s are quite impressive engines.