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AQ 120 B Adventure

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ddutton

Contributing Member
Here is my adventure so far. Engine rebuilt 9 years ago 150 hours on it. Start up this season squealing timeing belt tensioner puller frozen. Pulled apart and fixed. Put boat in water running OK but rough, basic carb clean. Out in boat fishing trolling, went to start it and sea water came poring out of carb. Back to shore oil in cylinders turned over regularly till new exhaust manifold installed. carb rebuilt engine runs well. Take it out, water poring out of raw water strainer. Plastics that raw water cap attaches to breaks. Questions for the gurus.
1) what could be blocked past the raw water cap (new exhaust manifold installed)
2) Can I get a new raw water cap, gasket and the part it attaches to. ( I see a lot of expansion tanks on ebay but no raw water part.
3) when I took it out oil pressure was zero. It ran so I assumes I might have yanked on the wire will replacing the manifold
I'm to the point of saying this engine is dead to me.
 
ddutton,

Damn! "If it wasn't for bad luck, you'd have no luck at all!" You definitely have had a string of major problems. I'd wait for Rick or Gary to reply. They have dealt with this stuff for years.

I can answer one of your questions,

"1) what could be blocked past the raw water cap"
Under the cap is the plastic strainer--that catches bits of seaweed, etc.. and needs regular cleaning. Next is that plastic housing where a few water lines connect. UNDER that plastic housing is the Heat Exchanger. Basically a cast aluminum housing containing the HEAT EXCHANGER CORE (it's a brass "widgit" that looks and acts like a little radiator). Seawater goes through one part of it and your engine coolant/anti-freeze mixture is cooled by flowing past the "other" part of it. The two should not meet. If they are mixing then you probably have a leak inside that Heat Exchanger Core (or element, whatever it's called). They get old and corrode or develop small pinholes, etc..They can also get plugged up with misc. stuff that gets past that plastic strainer. You should take it out and have a quality radiator shop "hot tank" it and do a pressure test on it--or just find a replacement. These parts get VERY PRICEY....
If you want to get it cleaned out and pressure tested, the best place to take would be a radiator shop that specializes in testing and repairing marine heat exchangers.
Hope this helps a little.
 
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Ok it may be worth saving. Took it out of water and ran. I have the dreaded cylinder 4 block corrosion. Exhaust leaking out. Rather than repeat can someone point to any of the many threads on cylinder #4 block corrosion.
Any answers on the raw water plastic housing, not strainer, availability?
How can I check if the oil alert sender is good?
 
OK after searching I have found the raw water housing, around $200.00, $275.00 in Canada. Now I need to decide do I get the housing only to find the housing below is plugged or should I just look for a used heat exchanger. Can you unplug the raw water portion of the heat exchanger?
 
ddutton said:
OK after searching I have found the raw water housing, around $200.00, $275.00 in Canada. Now I need to decide do I get the housing only to find the housing below is plugged or should I just look for a used heat exchanger. Can you unplug the raw water portion of the heat exchanger?
Click to expand...

At this point, it would be prudent to take the heat exchanger apart. You remove the plastic top portion, removed the top plate from the housing, carefully. The heat exchanger core comes out in one piece, approx. 9" tall, maybe 4" wide and about 2" thick. It's not very mysterious.
Get it out and take it to a good radiator shop that works on marine heat exchangers (As I mentioned in a previous post).
They will:
A) "Hot Tank" it to get it as clean as possible in a mild acid bath (I believe). This will clean most if not all the corrosion, old chunks of seaweed, etc. out of the core.
B) Then, they will do a pressure test on it to see if it has any leaks. They do this while the unit is under water. Any leaks will show as bubbles rising.
It's either that or pay about half the cost of the boat for a new heat exchanger.
I've had a few done in past years. Some failed at the pressure test phase--they are very hard to "repair" if they fail the pressure test.
I always run my stuff in fresh water after saltwater trips. You get a lot more hours out of the parts.

The plastic housing on the top can SOMETIMES be repaired if some skill is applied--JB weld, heli-coil treads, things like that. It's worth a shot if you're good at detail work and being creative with fixes. Next, run an ad on Craigslist looking for a used or dead _______whatever model and see if you can buy some parts. The mechanics who post here, Rich and Gary may have the part for sale. Also check EBay...hope all this helps.

P.S. If you can post a few pictures of that plastic housing, I should be able to tell you if it's "Fixable". I've repaired one or two and they can last for years longer if done correctly. Depends a lot on the damage. Or course, finding a good used one or a new one at a reasonable price would be nice!
 
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From bad to worse. Pulled heat exchanger off, bottom raw water drain was corroded so I was trying to clean it up and it fell apart. Drain came off element. Bottom filled with sand and crystallized salt, hence the circulation problem. It looks beyond repair, good thing I didn,t pay 300 for a strainer housing to put on a spent heat exchanger. Anyone know of a source of used ones. eBay only has expansion tanks.
 
BOC Member Ryan builds a shell and tube style heat exchanger for the Volvo Penta OHC 4's.
This solves all Volvo Penta OHC 4 cylinder OEM heat exchanger problems.

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Rick,

That is a sweet upgrade! That would save a lot of time, money and grief and provide a long term solution for DDutton's heat exchanger problem for sure.

I might be interested in one myself. It would make changing out timing belts, etc. much easier also. Can you provide contact info for Ryan?
 
ddutton said:
From bad to worse. Pulled heat exchanger off, bottom raw water drain was corroded so I was trying to clean it up and it fell apart. Drain came off element. Bottom filled with sand and crystallized salt, hence the circulation problem. It looks beyond repair, good thing I didn,t pay 300 for a strainer housing to put on a spent heat exchanger. Anyone know of a source of used ones. eBay only has expansion tanks.
Click to expand...

I may have one at the shop, let me know if you want it.
 
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