All of the hoses and fittings on my 502 MPIs were 1-1/4.

- incoming from sea strainer
- Merc pump in/out
- transmission cooler
- power steering cooler
- engine oil cooler
- thermostat housing inlet

The above is a what was stock on the starboard engine (no power steering cooler on the port engine).

All of that has changed since dumping the MPI, but it’s still 1-1/4 all the way through.

Agreed on not using aluminum. I think I’ve seen in brass as well as plastic.

I think I can make it work with Marelon fittings. Now I'm trying to determine if I can bend the 1-1/4" steel reinforced hose enough or if I should put in a pair of 90s after the pump as it goes back under the motor.....Gonna grab some hose today and find out.

The steel-reinforced hose will bend pretty well. It will depend on how closely you want the hoses tucked around the engine. Do not use the steel-reinforced hose on anything that you need to easily take apart. The steel wire will make removal of the hose from fittings quite frustrating especially if space is tight (ie twin engines). I'm using it from the strainer to the pump, and then the pump to the transmission cooler (for added stability). Everything after the transmission cooler is soft-wall with 90-degree fittings to keep things close to the engines.

yes I’m doing it right now. You can buy the supports, and balancer adapter from marineenginedepot.com (where I got all my stuff from).

i was facing some pretty similar situations not long ago and found some 90 and 180 deg 1 1/4’ aluminum pipe. What an inexpensive and very practical way to go and looked good. I’ll see if I can find a pic and post. I know you could use multiple fittings to achieve the same but why when these are available. Just an FYI.


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Keep in mind you can always utilize your local muffler/exhaust shop to bend up whatever you need. Very inexpensive and nonrestrictive.

I’ve gone to local plumbing places to buy brass fittings (not Home Depot or lowes, you need a Ferguson or plumbing supply shop those big box stores should be able to tell you who the big guy is in town). You can make anything that way just beware of weight and cost…

my raw water is 1.25” from seacock through strainer to pump and to heat exchanger(s) From the main heat exchanger is 1” hose routed around to exit manifolds b/c of the fittings on the exchanger itself.

Yes. I run the F6B-9 with truck accessories but I can't post a pic, don't have enough posts for that privilege.

Only takes 10 I believe. Suck down a 12 pack and post. Hah… 😂

Allright. I have a question in regards to that alternator bracket Mercruiser part# 862778. It appears that the only place for that to mount to, has a tube connected to it that goes to my heat exchanger (Horizon motor with FWC). Am I right on that? Is that where it would go? I think I could grind/modify the bracket to fit but before I do that I wanted to confirm if that is where it is supposed to bolt to. See red circled bolt in pic.



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