Freshwater/Saltwater boat - how to find out

Egor

Member
Jul 22, 2023
45
Monterey Bay, California
Boat Info
SeaRay 340DA 1999
Engines
Twin mercs
I am total noob in motor boats. I bought Searay 340DA in San Francisco bay , which is salt water. And I moved it to Moss Landing which is for sure even more salted. At the moment of purchase I did inspection, tried the boat, listen to motor and transmission, checked UIN and history and others - I did all precautions which I could imagine. what I did not checked - that the boat might be freshwater one. It was outside of my imagination.

Today I meet with technician who helped me with generator. And he surprised me, he mentioned that my boat does not have heat exchanges on engines and therefore it is pretty much freshwater boat. He said that heat exchangers are large clearly visible devices which usually located on top or side of the motor and are clearly visible.

I was given an offer to buy heat exchanger kits (2x$3100) and install them.

QUESTIONS:
1 How do I verify that my boat really don't have heat exchangers?
2 Does it make sense to buy those kits and install them? (I will use mechanic help to choose right ones)
3 Motors were factory refurbished recently, and probably spent in salt water like 30-40 hours. Will they survive? Should I try and somehow use "Salt Away" on them?

I would appreciate any advise on my case

Image of my motor: https://c2n.me/4j9aSRq
e3876-clip-1686kb.jpg
 
Two types of engines: “fresh” water cooled and “raw” water cooled. Fresh water means the block contains anti freeze like a car. Raw water is run thru a heat exchanger to cool the antifreeze. The raw water cooled skips the anti freeze and just runs sea/lake water thru the engine for cooling. In salt water environments it is common to have the fresh water cooled as the salt water is corrosive to the engine.

Looks like you have the fresh water version. Since they have been in salt water, it probably is too late to add the cooling kits. You should be flushing the engines after each run.
 
Two types of engines: “fresh” water cooled and “raw” water cooled. Fresh water means the block contains anti freeze like a car. Raw water is run thru a heat exchanger to cool the antifreeze. The raw water cooled skips the anti freeze and just runs sea/lake water thru the engine for cooling. In salt water environments it is common to have the fresh water cooled as the salt water is corrosive to the engine.

Looks like you have the fresh water version. Since they have been in salt water, it probably is too late to add the cooling kits. You should be flushing the engines after each run.
Golfman - good explanation, but, I don’t know if you caught that he stated the motors are rebuild with only 30-40 hrs. In my opinion converting these may not be too late.
Egor - I had the same motor in my 270 and had well over 1000 hrs always in salt. It’s not that uncommon to have raw water cooling in salt water, it’s just way better in my opinion to have a fresh water cooled system.
While I did not convert mine when I replaced the motor I always regretted that decision. Do a little more homework on this. I personally haven’t installed a kit on that motor yet, but hopefully others who have will chime in.
 
Thanks, Golfman, Thanks Boatrboy. I really appreciate your input.

I pulled up documentation, and found that boat inspection (which I did before purchase) states "cooling system - Heat Exchange"
Either inspector was inaccurate or Technician today was mistaken. I personally dunno what to think. Where on my boat can be heat exchanger and how it can look like? Please help me find it (boat and motor info in first post)

If no heat exchanger - I think will most likely install them.
I am also discussing it with www.orcamarine.com - that is the place who manufacturing installation kits and they have some real knowledge on the subject. Discussion in progress..
 
From that picture you don’t have a heat exchanger for the cooling system. As Golfman said you have sea water cooling.

You can look at this link and see what the heat exchangers look like. It appears the inspection report was not accurate

https://boatstoreonline.com/fwcmercfull.html
 
One of the most costly maintenance items are the exhaust manifolds and risers. Every five years they should be replaced if the boat is kept in a salt water environment. It appears that around 90 percent of engine replacements are due to exhaust manifolds leaking in salt water boats.
So, if upgrading the engine to closed loop cooling I'd also include the exhaust system in that closed loop system. Now the exhaust manifolds and risers will last indefinitely.
 
Golfman - good explanation, but, I don’t know if you caught that he stated the motors are rebuild with only 30-40 hrs. In my opinion converting these may not be too late.
Egor - I had the same motor in my 270 and had well over 1000 hrs always in salt. It’s not that uncommon to have raw water cooling in salt water, it’s just way better in my opinion to have a fresh water cooled system.
While I did not convert mine when I replaced the motor I always regretted that decision. Do a little more homework on this. I personally haven’t installed a kit on that motor yet, but hopefully others who have will chime in.
That depends on what is meant by rebuilt. If they used the same blocks, the deteriorating has been going on.
 
Thanks, Golfman, Thanks Boatrboy. I really appreciate your input.

I pulled up documentation, and found that boat inspection (which I did before purchase) states "cooling system - Heat Exchange"
Either inspector was inaccurate or Technician today was mistaken. I personally dunno what to think. Where on my boat can be heat exchanger and how it can look like? Please help me find it (boat and motor info in first post)

If no heat exchanger - I think will most likely install them.
I am also discussing it with www.orcamarine.com - that is the place who manufacturing installation kits and they have some real knowledge on the subject. Discussion in progress..
You’re reading way too much into it. You still have a heat exchanger for the transmission fluid, and I believe the engine oil, as part of the cooling system.

If you have freshwater cooling, you’ll have a heat exchanger at the top of the engine with a radiator cap, along with plastic antifreeze overflow containers. From your picture it looks like raw water cooled engines.
 
Now the exhaust manifolds and risers will last indefinitely.

I don't believe that is the case. The closed cooling system will cover the block and a lot of the internals but the manifolds and risers are still raw water cooled and used to expel the cooling water. So even with a closed cooling system you have to replace the risers and manifolds every 5 years or so if in saltwater.
 
Certainly looks like raw water cooling to me.

If you need a second bit of data to support this - take a look around the engine room for coolant reservoirs.

If you don't have these:
upload_2023-8-15_7-58-23.png


And none of these:
upload_2023-8-15_7-59-33.png


Yer raw water cooled...
 
I don't believe that is the case. The closed cooling system will cover the block and a lot of the internals but the manifolds and risers are still raw water cooled and used to expel the cooling water. So even with a closed cooling system you have to replace the risers and manifolds every 5 years or so if in saltwater.
They make kits that can include the manifolds and risers in the FW cooling loop. More $$'s but worth it if the owner desires to keep the boat for a long time.
 
I don't believe that is the case. The closed cooling system will cover the block and a lot of the internals but the manifolds and risers are still raw water cooled and used to expel the cooling water. So even with a closed cooling system you have to replace the risers and manifolds every 5 years or so if in saltwater.
What TT referred to is a full closed system, what you describe is known as a half system and the elbows will be raw water cooled in both.
 
Other than Illmor all the 'standard' marinized OEM closed cooled systems are the half systems. It's quite rare to find full closed cooling that include the manifolds and risers. I'm not sure of the cost to add these full systems, but risers and manifolds every 5 years isn't too expensive. Especially if you're doing the work yourself.
 
In a fresh water cooled engine risers can not be in the loop. The raw water needs to exit the raw water loop through the riser.

Keeping the exhaust manifold's in the fresh water loop is a very good idea, although not done on most boats because the cooling system can not keep up with the exhaust temperatures.

EDIT: I know the diesel guys are saying huh? Most if not all diesels have the exhaust manifolds in the closed loop side of things and don't really have "risers", but "shower heads" instead to let the raw water exit the system.
 
Don't confuse the term riser with elbow, risers can def, be part of the closed system
 
Other than Illmor all the 'standard' marinized OEM closed cooled systems are the half systems. It's quite rare to find full closed cooling that include the manifolds and risers. I'm not sure of the cost to add these full systems, but risers and manifolds every 5 years isn't too expensive. Especially if you're doing the work yourself.
There are a lot of OEM full closed loop Mercruisers around here. Hardin makes a nice aftermarket kit BTW.
Mr. Cool also made some nice kits but I don't know if they still do.
 
Don't confuse the term riser with elbow, risers can def, be part of the closed system

Risers are usually somonis with the outlet of the raw water when gas engines are discussed, but diesels most definitely have a riser that is not part of the raw water system and why I had the edit.
 

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