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On my 2003 Super Air, there is a factory-installed 2-port heater. I have never been that impressed with the heat output on these, especially on a v-drive where the hoses have so far to carry the hot water. On my old direct-drive, they were about 3-4' long each, and worked great at any engine speed. One night as part of party, we towed my boat alongside a floating dock and it spent hours idling, partly for music and partly because girls who were cold kept getting in and starting it up to run the heat. Idle only, tons of heat all the time.
So this spring, I changed the factory water return location to a y-pipe from Heater Craft to put the return right before (upstream) of the raw water pump. This is also how I had it setup in my old boat.
Last year, the heat worked ok, but it was hard to compare to the output of the old boat. It worked, mostly, but if you idled for too long, you'd have to just give it a little throttle to increase the flow a bit and heat would come back. It was not sustainable at just idle speed.
Now with the new setup, I am certain there is less heat coming from the heater core. One issue I've seen is that silt, or sediment from the bits of rust that come off the inside of the engine, can get trapped in low spots in the heater core and reduce the flow. So I removed the heater core and flushed it out with a hose thoroughly, both directions. I can't say whether anything came out. But I did notice that even with a fairly high-pressure hose just held up to one of the hose barbs by hand, the water flowed pretty slowly out the other side.
So I have a couple theories as to why the heater doesn't work as well as it did. And while the obvious culprit is the new return going into the y-pipe instead of the circ pump, I have to believe that's not the only thing going on. I really want to have better heat at idle, so I'm not sure what to do. I also know there's no reason why it shouldn't work with the y-pipe setup, if everything else is working properly.
One theory is that there is sediment that is hardened inside the inner (water) passages of the heater core, and flow is very slow. The heater core looks to be original, or at least very old. But it didn't build up just over the winter.... or was it just enough difference from last season... I kinda don't think so. Or is the inside of that heater core just a little corroded after 15 years, and slowing the flow of water? It's copper, though... so that shouldn't be an issue.
Another theory is that my impeller is tired; I do believe it was new at the beginning of the season, 2016 - the previous owner replaced the whole pump assembly because it was seized. My take on impellers is to replace every 2-3 years. Every year is overkill, but every "few" years is good. I've never had one fail, and this is also the general rule we used to follow at the marina where I worked. Now I like this theory because I DID change the return location for the heater, and it relies on the impeller creating strong suction. With my lake being ~55F still, it could easily cool the engine without being perfect. But maybe it's just not creating adequate suction for the heater, whereas before it was going into the circ pump.
A third, and sort of non-theory but possible solution is that I just don't get the heat output I want, even when it's working right, so why not just get a 3-port heater core (same heater core as the 4-port with one less opening, and less money). That gets me back to the supposed 40k btu output, up from the claimed 28k from the 2-port... and another vent if I want it. The core on the 2-port is probably half the size. I feel like that would make a big difference.
Last but not least, while the v-drive certainly allows for more passenger space, which I love, I'm kind of thinking the heater should be based in the stern, with vent hoses that extend up to the driver's seat and that area. This way, the air would have to travel farther but at least it would be more likely to be HOT. I feel like part of the problem is that the heater is too far from the engine.
But relocating the whole heater is kind of a last resort.
I guess now that I've thought this through, I should replace that impeller... I hear it's loads of fun on the v-belt v-drive Excalibur. And if that doesn't yield any results, then what?
So this spring, I changed the factory water return location to a y-pipe from Heater Craft to put the return right before (upstream) of the raw water pump. This is also how I had it setup in my old boat.
Last year, the heat worked ok, but it was hard to compare to the output of the old boat. It worked, mostly, but if you idled for too long, you'd have to just give it a little throttle to increase the flow a bit and heat would come back. It was not sustainable at just idle speed.
Now with the new setup, I am certain there is less heat coming from the heater core. One issue I've seen is that silt, or sediment from the bits of rust that come off the inside of the engine, can get trapped in low spots in the heater core and reduce the flow. So I removed the heater core and flushed it out with a hose thoroughly, both directions. I can't say whether anything came out. But I did notice that even with a fairly high-pressure hose just held up to one of the hose barbs by hand, the water flowed pretty slowly out the other side.
So I have a couple theories as to why the heater doesn't work as well as it did. And while the obvious culprit is the new return going into the y-pipe instead of the circ pump, I have to believe that's not the only thing going on. I really want to have better heat at idle, so I'm not sure what to do. I also know there's no reason why it shouldn't work with the y-pipe setup, if everything else is working properly.
One theory is that there is sediment that is hardened inside the inner (water) passages of the heater core, and flow is very slow. The heater core looks to be original, or at least very old. But it didn't build up just over the winter.... or was it just enough difference from last season... I kinda don't think so. Or is the inside of that heater core just a little corroded after 15 years, and slowing the flow of water? It's copper, though... so that shouldn't be an issue.
Another theory is that my impeller is tired; I do believe it was new at the beginning of the season, 2016 - the previous owner replaced the whole pump assembly because it was seized. My take on impellers is to replace every 2-3 years. Every year is overkill, but every "few" years is good. I've never had one fail, and this is also the general rule we used to follow at the marina where I worked. Now I like this theory because I DID change the return location for the heater, and it relies on the impeller creating strong suction. With my lake being ~55F still, it could easily cool the engine without being perfect. But maybe it's just not creating adequate suction for the heater, whereas before it was going into the circ pump.
A third, and sort of non-theory but possible solution is that I just don't get the heat output I want, even when it's working right, so why not just get a 3-port heater core (same heater core as the 4-port with one less opening, and less money). That gets me back to the supposed 40k btu output, up from the claimed 28k from the 2-port... and another vent if I want it. The core on the 2-port is probably half the size. I feel like that would make a big difference.
Last but not least, while the v-drive certainly allows for more passenger space, which I love, I'm kind of thinking the heater should be based in the stern, with vent hoses that extend up to the driver's seat and that area. This way, the air would have to travel farther but at least it would be more likely to be HOT. I feel like part of the problem is that the heater is too far from the engine.
But relocating the whole heater is kind of a last resort.
I guess now that I've thought this through, I should replace that impeller... I hear it's loads of fun on the v-belt v-drive Excalibur. And if that doesn't yield any results, then what?
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