quick heater core question

[SoldTheBayliner]

Hi, sorry, I'm sure this gets asked every year... I tried searching I swear.

Apparently I didn't have the lung capacity I've had in the past when winterizing last year... wet feet at the driver's seat first time out this year, leaky heater core. Booo.
Boat is a 2000 SAN.
I bypassed the heater core and took out the heater unit... The previous owner made that even more fun by wrapping the whole thing in stereo amplifiers. I have yet to pull the core out of the box and take it to the auto parts place to try to match it up. I hear that's way cheaper than buying a Nautique-specific one.

My question is: does it matter which hose goes on which hose barb on the heater core? I can't imagine that it does, but maybe there's flow from one or the other and you want input at the top and outlet at the bottom...?

Follow up question: When blowing out the heater core from the engine end of those hoses, I'd assume it would be more effective to be blowing into the upper hose, and pushing water out of the lower hose. Which hose is which at the engine end? There's one up near the water pump, and one at the lower engine block on the starboard side. Engine is the 5.7 Apex. Maybe I was blowing into the lower hose and trying to push water uphill out of the core, and that's why I had issues.

Thanks!!

[t.franscioni]

I wouldn't think it matters which hose goes where but would think its best to attach supply hose to top and return hose to bottom to aid in pushing any debri through the system that may come in through the raw water pickup.

The hose coming off the bottom of the block will be the hot water supply to the heater.

[t.franscioni]

I will take a look at my heater core to see if there is a specific inlet and outlet as I have my boat torn apart and heater is sitting on my bench. Heater Craft is the manufacturer they have a website you can order direct from so you can compare replacement cost vs repair cost.

[SoldTheBayliner]

Thanks! I didn't think to look to see if it's labeled... I'll check that out also since mine is on the workbench (pulled it out and just attached the hoses together to bypass it for the time being... lake plans this weekend).

I was thinking the opposite on the hoses... figured it would flow out of the high spot on the motor and back into the low spot. But I really have no idea....

[scottb7]

I don't think it matters either way for use or blow out if you blow out with approximately the psi they recommend.

[SoldTheBayliner]

What PSI is that? I've done it with a compressor and with my mouth with no issues until this winter... I'll pay a bit more attention this year though...

I found an exact match for size in the catalog at Napa Auto Parts... fits a few older Ford models. $26 compared to $70 or $80 for the "nautique" part. They had to order it so I'm not sure it will fit exactly without altering the box at all. I'll pick it up today or tomorrow.

[scottb7]

http://heatercraft.com/content/Insta...tal_Marine.pdf

I think it says do not exceed 35 psi.

p.s. someone somewhere gave the part# to get from auto shop for replacement.

[SoldTheBayliner]

Here's what I wound up with from Napa. I had to drill out the rivets on the sides of the heater box that were holding a kind of little bracket thing that the old heater core slipped between (like to keep it from shifting around in the box). The new core slid in so snugly that that's not going to be an issue anyway.

Then the little "U" cutouts for the inlet and outlet didn't line up exactly... super close:



So I had to take a dremel to those "U" cutouts. No big deal:





$28 at Napa. Here's the part #