I have been on an extensive journey trying to manage the build-up of salt deposits within the cooling system of my Honda outboard motors, between 7.5 HP and 15 hp, As a normal management of these motors, I have always have always run them in fresh water after marine use to "flush" them clear of any salt residues. What I have discovered in all of them, that as much as I try to clear these motors of salt residuals, when I access the water jacket pathways inside the motors to change thermostats, etc., I still find caked salt crystallization within the interior of the motors. My first clue is usually a reduction of flow through the water flow indicator hose (pee hose). The 15 hp Honda hose connects to a plastic nozzle fitting at the exit point, which constricts the pee flow, as "kidney stones" try to be passed, which complicates water discharge considerably, but the constriction gives a warning that all is not well within.
On all of my motors, when I have removed the intake manifold casting, I have found precipitated salt deposits constricting the water flow throughout the motor. On one of my motors, a 7.5 hp, these caked deposits caused overheating in the unit, yet for years, I have religiously flushed the motor with fresh water after any marine use.
Puzzled, when I last changed the thermostat, I cleaned all salt deposits reachable with the intake manifold removed, but was left wondering how much salt was left within the motor that I could not see. I used mini-bottle brushes and all sorts of physical tools to remove any crystalized salt that I could find. I also ran vinegar down the passageways accessible with the intake manifold off, but never had a way to figure out how many areas that were inaccessible to my labors.
I am by no means an outboard mechanic, but I have enough background in chemistry to understand solutions at some level, crystallization forces and bonding, heat effects with solubility, and electrolysis.
I worked on my engine blocks diligently, injecting vinegar solutions, flushing with fresh water, digging out any loose crystalized salt, etc. before reassembling the motors. My end results were greatly improved water flow, and a return to normal operation. I noted that the vinegar solutions used had the effect of turning the hard-crystalized salts into a more friendly slushy aggregation when I encountered crystals in the process of reassembly. Visualize here, slushy snow rather than a salt cake.
Building upon this observation, I am reasoning that a continuous program of post-marine use maintenance should involve some form of treatment that re-dissolves crystalline deposits rather than simply a quick freshwater rinse. the reason here is a basic chemistry law that requires an energy bump to convince a crystalized salt to give up its tightly bound structure and return to a solution form.
Following this train of thought, crystals are more easily released into solution in a heated environment. An acidic environment also discourages crystal formation. If that is the case, using a warmed acidic flush should help to remove crystals of salts from the internal areas of the motor, without tearing down the motor or finding all of the inaccessible channels.
I used this chemistry logic and put it to use on my three motors. After some initial purging in a vinegar solution in my test tank, (clean garbage can), I was able to capture little bits of slushy crystalline shards. Think passing kidney stones here. After a time, the kidney stones dissipated somewhat, and all motors began to pee like 8-year-old boys.
So in a sense, I have found a way to manage salt build-up in my motors. However, here is where I would like input from the brain trust.
I just ran my 7.5hp for sea trials following some major maintenance. It Peed OK, but I was still unsure if all cooling channels were clear. I was freshing out the motor in my "tank", the motor was at full operating temperature, with thermostat open, and I looked at the pee hose. I said to myself, "Self, what would happen if I back-flushed the water pathway with vinegar right now with the warm engine? The vinegar should find its way completely through the cooling system back to the water pump, dissolving any salt left in the system."
With little to lose, I did just that, a mouthful at a time upstream into the pee hose. I let it sit for a bit, and then restarted the motor. Granted, I may be biased, but I believe I had improved water flow even more. I have no way to know how much residence time I had within the motor for the vinegar, but I think I ran enough vinegar into the motor to at least wet the cooling surfaces.
I am thinking that this little step after marine use might be a simple way to reduce both residual salt deposits inside the motor as well as discourage the formation of future salt deposits. the only downside I can see is that vinegar , being acidic, will react with any sacrificial anodes (zincs) inside the motor, shortening their life somewhat. To lessen that concern, after letting my vinegar flush sit for awhile, I did a final rinse with fresh water to purge the acid.
My 7.5 has no internal anodes, but my 15 hp does, which reminds me: I need to locate it and change it.
There are a lot of really smart folks on this site: what do the real guys think here? I am happy to be sent back to chemistry class, which is way easier than dealing with an overheated motor in rough seas.
Best to all, and thank you in advance for any inputs. Glen Moore, Seattle.
On all of my motors, when I have removed the intake manifold casting, I have found precipitated salt deposits constricting the water flow throughout the motor. On one of my motors, a 7.5 hp, these caked deposits caused overheating in the unit, yet for years, I have religiously flushed the motor with fresh water after any marine use.
Puzzled, when I last changed the thermostat, I cleaned all salt deposits reachable with the intake manifold removed, but was left wondering how much salt was left within the motor that I could not see. I used mini-bottle brushes and all sorts of physical tools to remove any crystalized salt that I could find. I also ran vinegar down the passageways accessible with the intake manifold off, but never had a way to figure out how many areas that were inaccessible to my labors.
I am by no means an outboard mechanic, but I have enough background in chemistry to understand solutions at some level, crystallization forces and bonding, heat effects with solubility, and electrolysis.
I worked on my engine blocks diligently, injecting vinegar solutions, flushing with fresh water, digging out any loose crystalized salt, etc. before reassembling the motors. My end results were greatly improved water flow, and a return to normal operation. I noted that the vinegar solutions used had the effect of turning the hard-crystalized salts into a more friendly slushy aggregation when I encountered crystals in the process of reassembly. Visualize here, slushy snow rather than a salt cake.
Building upon this observation, I am reasoning that a continuous program of post-marine use maintenance should involve some form of treatment that re-dissolves crystalline deposits rather than simply a quick freshwater rinse. the reason here is a basic chemistry law that requires an energy bump to convince a crystalized salt to give up its tightly bound structure and return to a solution form.
Following this train of thought, crystals are more easily released into solution in a heated environment. An acidic environment also discourages crystal formation. If that is the case, using a warmed acidic flush should help to remove crystals of salts from the internal areas of the motor, without tearing down the motor or finding all of the inaccessible channels.
I used this chemistry logic and put it to use on my three motors. After some initial purging in a vinegar solution in my test tank, (clean garbage can), I was able to capture little bits of slushy crystalline shards. Think passing kidney stones here. After a time, the kidney stones dissipated somewhat, and all motors began to pee like 8-year-old boys.
So in a sense, I have found a way to manage salt build-up in my motors. However, here is where I would like input from the brain trust.
I just ran my 7.5hp for sea trials following some major maintenance. It Peed OK, but I was still unsure if all cooling channels were clear. I was freshing out the motor in my "tank", the motor was at full operating temperature, with thermostat open, and I looked at the pee hose. I said to myself, "Self, what would happen if I back-flushed the water pathway with vinegar right now with the warm engine? The vinegar should find its way completely through the cooling system back to the water pump, dissolving any salt left in the system."
With little to lose, I did just that, a mouthful at a time upstream into the pee hose. I let it sit for a bit, and then restarted the motor. Granted, I may be biased, but I believe I had improved water flow even more. I have no way to know how much residence time I had within the motor for the vinegar, but I think I ran enough vinegar into the motor to at least wet the cooling surfaces.
I am thinking that this little step after marine use might be a simple way to reduce both residual salt deposits inside the motor as well as discourage the formation of future salt deposits. the only downside I can see is that vinegar , being acidic, will react with any sacrificial anodes (zincs) inside the motor, shortening their life somewhat. To lessen that concern, after letting my vinegar flush sit for awhile, I did a final rinse with fresh water to purge the acid.
My 7.5 has no internal anodes, but my 15 hp does, which reminds me: I need to locate it and change it.
There are a lot of really smart folks on this site: what do the real guys think here? I am happy to be sent back to chemistry class, which is way easier than dealing with an overheated motor in rough seas.
Best to all, and thank you in advance for any inputs. Glen Moore, Seattle.
