Where do I connect my heater lines? 98 SN - GT40

[beamons]

Hey everybody,
I need help in figuring out the best place to connect my heater hot water line and the return line. Can someone tell me or better yet, upload pictures?
I know that the low idle wye is supposed to be the best way but where do I put it?
Thanks in advance.

[wtrskrs]

I have a 97 (current project boat) and had a 96 (bought new, sold last year when I picked up the '97), both with a GT40. The line to the heater comes off the top of the block in the front to the starboard side of the distributor. There is a temp sensor there; you'll need a T. The return can go several places. One is to the elbow below the engine circulation pump. Another location is the starboard block forward plug (behind the raw water pump). The third is to use a Heatercraft Y connector. This is placed in your raw water hose just BEFORE the intake side of the raw water pump. The suction of the raw water pump will pull water through the heater core. I personally don't like that because you are constantly pulling hot water out of the engine and replacing it with cold water (not letting your thermostat keep the engine temp uniform. Probably not an issue, but I don't like it (and I wanted my water as hot as possible for the heater. So I put a hot water circulation pump in line in the hose to the heater. This keeps the water flowing at idle so I get heat, with the added benefit that I can shut my engine off and still get hot air for quite a while (nice when another boat is in the course and you are waiting.... Started to take pictures, but easier to take a video (a bit disjointed; I only had 4hrs of sleep last night and been non-stop all day so a bit tired...). Here's the link. https://youtu.be/lRETcn1n7j4

Let me know if you have any questions.

Gordon

[beamons]

Gordon,
Thank you. That was super helpful. Great explanation and very informative.

To anyone looking for this info in the future this is the clearest and simplest explanation of where to hook up you heater on a GT40.

Brian

[functionoverfashion]

The third is to use a Heatercraft Y connector. This is placed in your raw water hose just BEFORE the intake side of the raw water pump. The suction of the raw water pump will pull water through the heater core. I personally don't like that because you are constantly pulling hot water out of the engine and replacing it with cold water (not letting your thermostat keep the engine temp uniform. Probably not an issue, but I don't like it (and I wanted my water as hot as possible for the heater.

Gordon

First, I want to say I think your system sounds like it works great - clearly it does! But I don't know what you mean by 'not letting your thermostat keep the engine temp uniform' - there is always a flow of water coming in from the lake and going out through the exhaust, no matter what. As your engine warms up, the thermostat opens to allow more of this cold lake water to mix and flow around the engine to keep it around 160 or whatever. It's always replacing hot water with cold. So I don't see that a heater would make much difference, and if anything, it's mixing some warmer-than-lake-temp water in with the lake-temp water just before the RWP... but either way the thermostat is controlling how much fresh (cold) water comes in.

I'm not really arguing with you and I think your system is perfectly good. But I've had great luck with the Y pipes and don't really see any problem with them except the cost.

I do really like how an inline circ pump gives you heat longer after the engine is off. Normally you can feel it getting colder within a minute or two with the engine off.

Also: you can use the block drain as a hot water source, rather than building a T at the top of the intake manifold. Just get a single 3/8NPT x 5/8" hose barb adapter. On that note, I've had a hard time finding weird plumbing fittings locally, and found this great - and very literal - website: http://fittingsandadapters.com/

[wtrskrs]

First, I want to say I think your system sounds like it works great - clearly it does! But I don't know what you mean by 'not letting your thermostat keep the engine temp uniform' - there is always a flow of water coming in from the lake and going out through the exhaust, no matter what. As your engine warms up, the thermostat opens to allow more of this cold lake water to mix and flow around the engine to keep it around 160 or whatever. It's always replacing hot water with cold. So I don't see that a heater would make much difference, and if anything, it's mixing some warmer-than-lake-temp water in with the lake-temp water just before the RWP... but either way the thermostat is controlling how much fresh (cold) water comes in.

I'm not really arguing with you and I think your system is perfectly good. But I've had great luck with the Y pipes and don't really see any problem with them except the cost.

I do really like how an inline circ pump gives you heat longer after the engine is off. Normally you can feel it getting colder within a minute or two with the engine off.

Also: you can use the block drain as a hot water source, rather than building a T at the top of the intake manifold. Just get a single 3/8NPT x 5/8" hose barb adapter. On that note, I've had a hard time finding weird plumbing fittings locally, and found this great - and very literal - website: http://fittingsandadapters.com/

All great points.

First, on the water not being as uniform, as you mentioned, once the engine is warm, the thermostat is always letting in some cold water to keep the temp at 160 (or whatever). My re-circulation pump is rated at 4.5gpm although let's assume it is pumping 3gpm through the heater core. Assuming the Y connector is pulling the same 3gpm, then there are an additional 3gpm of cold (okay, mixed, so cool) water into the engine than the thermostat is expecting. I have no idea how many GPM a thermostat pulls into the engine at normal operating temperature (without a Y) to keep it at that temp (obviously lake temp will impact how much is needed). But I'm just guessing that if I could put a temp probe a little past where the cold water comes in past the thermostat, there would be a noticeable difference in the temp at that location between an Y and no Y. Of course, without the Y, if the thermostat is pulling in 10GPM of cold water when at operating temperature, then three more gallons doesn't make that much of a difference. But if it is only needing two GPM to maintain temperature and we're forcing 3GPM in, then it is harder to stay uniform throughout the engine. I may be way off base (all speculation on my part), but I also ski in the winter when the water temp drops below 50 vs the summer when it could be near 80. So I suppose this is just me being anal, but I liked the circulation pump route better for overall efficiency. And, with the Y, warm up times are going to be longer. And if you also have a shower or hot water line for a 'hot tub' like we do that 'uses' hot water (whereas the circulation pump 'recycles' warm water), I'd be replacing water for the heater through the Y plus the water I'm pulling for the hot tub (unless I put a valve on the heater hose to stop heater core flow while pumping the hot tub). So it would take that much longer to fill the tub and the engine would be running that much colder. That said, putting a Y in and not dealing with the pump, relays, etc., would be VERY nice and extremely simple. But if you go to HeaterCraft's website, while they do have the Y, they also sell a re-circulation pump option (quite expensive so I bought my pump on Amazon for less than half). In talking to them, they conceded that a circulation pump is the best option so offer it in addition to the Y. All that said, my boat (and my previous boat) has by far the best heater in our club....

Heatercraft recirculation pump: https://heatercraft.com/products/hea...nt=37942849803
Heatercraft Y: https://heatercraft.com/collections/...nt=37946119115

(note: The heatercraft pump is 3gpm; I got a 4.5gm pump since I have the larger heater core. Also note that these are demand pumps (valves), not centrifugal. I've used centrifugal on my old boat and it was not bad but not great, but since Heatercraft uses a demand pump, I went with the same thing to make sure water was pushed through with some pressure. Works better, but keep in mind demand pumps are noisy. I can hear it in the background at idle whereas I couldnt' hear anything with the centrifugal pumps. Just FYI if you are looking into pumps)

As for the locations to tap hot water, if you have the Y or a pump, then you can probably tap almost anywhere. I initially (on my old boat) didn't have a Y or pump and of course the water got cold at idle and had to warm back up when at speed (when you're driving the course, you're at speed for less than a minute). I put it at the top just before the thermostat since that is where the hottest water should be. While my heater (four hose 40kbtu) puts out a lot of heat, it can only heat up so much from ambient air temp. So when the ambient air is really cold, I want to squeeze as much heat as I can out of it. When the air is in the 40s, I'd love more heat than it can give.

BTW, cool site for fittings and adapters! Thanks!!

Oh, side note. I just redid my upholstery and I installed seat heating elements in the driver and observer seats. I don't need the heater anywhere as much as before; it is incredibly nice!!.


Finally, I should spent more time thinking about my set in the course this morning than writing this email; I've got lots of stuff to fix!!!

[wtrskrs]

.. but either way the thermostat is controlling how much fresh (cold) water comes in.

Ah, one other thing: This is very true about the thermostat controlling how much fresh water comes in based on engine temperature. However, a marine thermostat also has to let in more water if more water is being pulled out (shower, heater with Y, etc.). If more cold fresh water to replace 'used' water is coming in than the engine needs to stay at normal temp, the engine temp goes down as more cold water comes in. I also learned (from personal experience) that a regular automotive thermostat does NOT work in a boat environment where the engine is cooled by the lake/river (as opposed to a closed loop cooling system with a heat exchange). I don't know specifically how a boat thermostat allows more water in to replace water from a shower, etc., but an automotive thermostat doesn't work correctly.

Just a suggestion that you always opt for a marine thermostat rather than like me trying to be cheap......

[functionoverfashion]

This is way more discussion than I've ever seen on heaters. Don't get me wrong, it's great! Around here, it's cool most nights, and a lot of the days when we use the boat. I use it way more than I would have ever thought. SO many times, it's made the difference between my wife being willing to come out, and wanting to stay home where it's warm. I've put them in a few friends' boats and they rave about what a difference it's made, especially for early/late season or even mid-summer, late evening water time.

In my old boat, I had a 4-port heater like you have, and the heater core was under the spotter's seat, so that was a very warm area. Tons of heat, and short runs from the engine (I did have a Y also).

The v-drive has a WAY longer run to the heater core, so I put in a Y and a bigger heater core within a year of having the new (to me) boat. I've always wanted to do a circ pump, but didn't want the added complication - and didn't need it in my boat. Good tip on the noise, I'd want the quieter pump myself. We do a lot of idling around at night, any extra noise would be unwelcome.

I'm not sure we'll ever get to the bottom of the question of how the recirculated water affects or doesn't affect engine temp, because there are too many other variables, not the least of which is lake temp, but also: engine speed/load, heater placement and size, fan speed (to some extent), water source (e.g. block or intake manifold) and so on.


Oh yeah, and 'fittingsandadapters.com' is the best. It's like 'clipsandfasteners.com' which carries a huge variety of specialty automotive bits like trim clips and ... well, fasteners. It's mind-blowing if you've ever had a hard time finding a cheesy plastic bit that broke off when you pulled off a door card or random piece of trim on your car. Two of my favorite parts-supplying websites.

[SilentSeven]

Adding photos on how my heater is connected. I've done nothing but enjoy it as it came this way when I purchased the boat. Yes, I need to replace the hoses and I'm not looking forward to that

https://imgur.com/a/JADk1rS

[Tom_H]

Not to be too nitpicky, but just want to point out that the thermostat is the water outlet for the block and not the inlet that is being inferred here. From the raw water pump water either enters the block at the circulation pump (via the J-tube) or is shunted to the exhaust based on how much hot water the thermostat is letting out. Using a heater Y won't have any detrimental effects on engine temp. That being said, there's no good reason to run both a y-fitting and a heater circulation pump.

If I were plumbing one in, I'd probably pull the hot from a block drain and return with a y upstream of the raw water pump for the vacuum assist

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