Heater Install Q's

Getting ready to install by 4 outlet heater. This is going in a 07 Supreme V232 with a Merc Black Scorpion. Got just a couple questions that I couldn't find answers to.

1) Electrical Connection. Where do I get the power for the sucker? From what I remember underneath, the battery runs to a mounting post and then several wires to the fuse panel, then back to the components.(It's further confused because I have a dual batt setup) There are also some red wires with female connections on them that look fairly thick just hanging around. Can't remember where they come from other than just looking like they come from a tangle of wires. Will be adding a fuse of course.

2) Connecting the water supply lines. Can I just loosen the screw clamps and pop off the hoses that are going to what I think is the thermostat housing? It might spill a little water, but once they are out of the way, it'll be a lot easier to make the connections. Can't imagine there is a prob with doing this, but I want to make sure. Also should I use teflon tape/plumbers putty on the connections? I have already bought ball valve shut offs.

Other than that, the install doesn't look too tough.

Thanks much.

1) For power you can go directly to the engine start battery using a switch and fuse in line or get power from an accessory switch under the dash.

2) As far as water connections are concerned these pages are from Mercury install manual for Black Scorpion.

1. I ran a 4 ga power wire to a distribution block under my dash for accessories. I originally had the motor running straight through the switch (I used a switch in my dash) but it got wicked hot from the power draw, so I wired in a relay. The high setting pulls quite a few amps.

2. I don't remember exactly where I pulled the hot water from, but I returned it into the v-drive, which feeds into the raw water pump. I'll take pics later. Ball valves are a great idea, as well as teflon tape.

I am going to redo the return into the v-drive, as I am going to add a female hose connection with a valve so I can connect a hose straight in when running the motor out of the water or use it as a back up with a ballast pump when my impeller goes.

Yea, they put a coil of red and black wire in the heater kit that is real small gauge. I don't know if it can handle 15 amps. That wire is supposed to power the switch which then powers the unit. It is wierd because then the wires from the switch to the heater unit are much beefier.

I think returning to the v-drive is a good idea. Returning to the outlet side of the v-drive may be best so the v-drive doesn't overheat. That could probably be done by adding in a simple T fitting to the outlet. I guess I am not sure about why then people are buying a seperate hose fitting to return the water before the impeller. Seems like a lot more work that putting a T on the V-drive.

Todd, my above post is directly from Mercury install manual for the Black Scorpion Engine. The two 1/2" NPT plugs on either side of the thermostat housing go to your heater inlet. The 1/2" plug on the side of the circulating pump goes to the outlet of the heater. These plugs are there just for installing a heater and this is where all the factories that install Mercury motors install them. Just go to your local auto parts store and get two 1/2" NPT to 5/8" hose barb.

I pulled the hot water from the thermostat and returned it as shown here. The ball valve to the left is the shut off of the feed and the one to the right is for the return. I also wired in a blower fan as I have one run that goes all the way around the nose of the boat.

Dumping hot water into the v-drive is a bad idea. The water entering the v-drive is supposed to be lake temp, so let’s just say 75 degrees for the sake of discussion. The heater return is dumping 160-180 degree water in to the v-drive increasing the operating temp of the v-drive. Now the hot water mixed with lake water enters the raw water pump that uses a rubber impeller that was not designed for water this hot. From the raw water pump the water enters the heat exchanger for the transmission thus not allowing for the absorption of as much heat from the transmission fluid. Reductions of 40 degrees in your transmission fluid temperature can double the life of the unit. After the transmission the water (which is now supposed to just warm and in Eric's boat is now probably hot) enters the fuel cooler, key word here being cooler. So instead of cooling the fuel you are pre-heating it. After that it’s all the same as to inlet water temp. It’s your boat and you can install the heater any way you want, just thought I would give you a heads up!

I had never really thought about it that way. It makes sense that even water a few degrees warmer would impact the whole system. Thanks for the heads up. I thought I would be making life easier this way! So take my pic as a "What not to do!"

(Message edited by rowdy on July 09, 2009)

No problem just extend your return hose to the side of the circulating pump on the front of the motor. Live and learn

Cool Brandon, are these pages from the service manual?

No, its from the installation manuals.

Just for the next person's information, I found it impossible to install a shut off valve right out of the supply and return ports on the engine. There just wasn't enough room to install any combo of brass fittings. Instead I installed the hose barbs to the engine, ran a couple feet of hose and installed the shut-offs there. Then ran more hose to the core.

I have been watching this thread and wanted to input on something that may help for the long runs or more tubing needed.
I installed a 4 port heater in my boat. The 2 longest runs were to the drivers side since they went all the way around the nose of the boat. Heatercraft only sent 25 foot total. I started looking for more hose at lowes/home depot, etc. They use a 3 inch opening.
After wandering around wal-mart I was in the automotive/rv section. I found tubing that works perfectly and is more insulated than the heatercraft tubing they sent. It is RV Sewer hose. I picked up 20 feet of Rv sewer hose for about 7 bucks. It is 12ml thick and there is virtually no heat loss and I didnt have to install a blower fan. My longest run was to the rear drivers side and a hot tube at that. I lost all heat since I used the heatercraft tube and just had cold air blowing. I then bought 20 ft of Heavy duty rv sewer hose that was 15ml thick and re-ran my lines. Now I have hot air coming from all the tubes and they are all consistent airflow instead of some having more pressure than others. Just thought I would mention that as an option for people that are adding this to theirs in the future. Also, the Mambe Blanket is a great investment too. The plug in heater ports on the blanket are rockin and its a great blanket all around.

I too used rv hose on my long run around the nose. It's cheap, easy to use and doesn't crush easily. I still elected to go with an inline blower, as I was finding there was still too much friction loss.

Brandon, I ran the boat this weekend with the water lines to the heater shut off and noticed a significant difference in the way the motor ran. It ran 10-15 degrees cooler. Also, I think the heater line was dropping an embolism of air into the raw water intake when the motor would start, and who knows what kind of trouble that could bring. Thanks again for the heads up.

I didn't see any need to run around the nose for my setup, my boat must be different as I ran right up the starboard side to the heater.

How do the flexible air hoses get attached to the heater unit itself? Zip ties?

Also is there a place to buy a rocker switch that will fit right into one of the rectangular dash openings?

I had to run mine around the nose unless I wanted to drill into the ski locker and then back out to the heater for my application. We put a 700lb sac in there so it would be crushed the first time we used it. My front bow seats are coolers as well so they are totally sealed. As far as attaching the hoses to the heater, yes, use the zip ties they provided but make sure your zip tie and tube is below the lip on the heater ports. If not, it will come right off. Snug down the zip ties. Also, after talking to heatercraft, they mentioned hooking the longest running hose closer to the water in lines instead of the last port. There could be a little heat loss if you have it farthest from the water lines and a long run of tube. I dont know about the rocker switch. I have heard people running a 3 position switch that just controls 2 speeds (low and high would be my guess) that matches the other switches. I put the heatercraft switch beside my cupholder on the drivers side and it turned out pretty good. Sorry about the crappy camera phone pic

Todd, what kind of dash switches do you have? I put a 3 position in my dash and wired the heater to high and med. I didn't see a point to low, especially in an open air environment.

I have the rectangular rocker switches, pretty much the standard ones I think. I have several blanks were I could put the switch.(no unused switches though) I would be more than happy with just high and medium if I could find a switch.

Not my dash, but almost the same. Hopefully u can see

Brandon, how's the low rpm performance of the heater when it's plumbed to that return?