Here's a pic from today of where the heater connections are at the engine. (V drive) The two black hoses that come vertically off the back of the engine are the hoses. The supply one has a tap (red hose) directly to a pump to the shower nozzle. NOTICE THAT BOTH BLACK HOSES ARE KINKED. They need 90 deg elbows right there. That will DEFINITELY affect heater performance. If you have that problem, I'd fix it first, I certainly will.
I will pull these hoses off to winterize the heater next year, blow some compressed air through the heater core. I'll probably be replacing that as it was probably not winterized at some point. I have to move the heater to fit a sub in there anyway.
I am not sure if our heaters are hooked up the same way that they are on other boats. I will say that the two pipes where the water comes out on our M1UZ engines is just like most auto applications.
How big is the large part of that hose fitting they sent you Shawn? If it is over 1" I would think that they may hook up heaters differently on other engines, like right in the thermostat hose. That's my guess. If not, maybe there's a tap off the 5/8 or so heater hose up under the dash for the hot line, and maybe that's a bigger fitting. You might ask a local boat dealer. Mine has no idea, they never sell boats with heaters here. THat kills me, except for one month year, there are sunny 70 deg days once in a while with no wind. MINE's gonna work, and blow hot.
