My boat stays in salt water all year and I don't have fresh water to the mooring to flush with. The motor is a 454 Mag MPI that has closed cooling from new, I am just fitting a set of Keith Eikert cast aluminium headers with stainless twin wall dry to the tip tails.

I would like to plumb the exhaust manifolds in to the fresh water circuit in order to prevent corrosion and would dump the salt water in to the stainless tails which should be pretty corrosion proof.

Will my heat exchanger have enough capacity to cope with the extra demand?

I am running manual hydraulic steering so the power steering cooler is redundant, I was thinking of plumbing that in series with the main heat exchanger, would that help?

I am boating in the UK where sea temperatures aren't exactly warm so that would probably help too!

Will I get away with it?

Thanks

Paul.

This is something that can be done and with your water temps and lower power level of a 454MPI its should not be difficult. I would advise talking via email to a couple of comapnies like maybe Monitor Industires and Sen-Dur Products both in Florida and have them verify if your current heat exchanger size is adequate to handle the added heat production of the exhaust manifolds. I think they actually make higher capacity heat exchangers that are physically about the same size of your existing unit. These have more tubes to provide more heat exchange and you will also have to make sure your raw water pump and system are up to the task.

Best Regards,
Ray @ Raylar

Thanks Ray, I will email them.

Forgot to mention that I am installing a cam and full valve train from Bob Madara together with a Holley HP Efi and Vic Junior from Alex Haxby - hoping to make close to 500hp. that might make the coolant temps climb a bit...

Bob can help you with the plumbing Bro -

I have Gill exhausts and closed cooling....salt water goes in hull, through exchanger, and dumps into top SS portion of the Gill risers and out the boat.....water Temps have not been an issue with bone stock merc motors. Thermo needs to be 160 (versus the 140) in closed cooling. dont know if MPI is different. Good luck