Cooling System

Hello all, first post for me.* I'm working on a 36' International with twin Ford Lehman 80s.*** We weren't getting much water from the starboard exhaust, so after checking the strainer we opened up the sea water pump and found a damaged impeller.* After replacing it, we checked for impeller pieces in the rest of the system.* Salt was caked very heavy on both inlet and outlet sides of the heat exchanger for the engine water cooling system.* Maybe meaning there's been low flow for a while?*

After getting out as much debris as we could find, we started it up and initially got good flow.* Then at higher rpm (1800) it would start to heat up.* It would cool off at 1200 or so.* Back to the dock, checked the intake, did find some sea growth and cleaned it all out.* Rechecked the strainer, found some shellfish, cleaned out.* At this point, I was sure flow would be restored, but unfortunately was disappointed.** I opened both sides of the transmission and engine cooling water heat exchangers, both still look good.* The oil cooling heat exchanger is hard to get to, but its up stream of the seawater pump and I think flow is fine there.*

The seawater pump is Jabsco.* I've seen in other threads that a change to a Johnson is recommended.* With the cover to the pump off, and turning over the engine with the stop button depressed, the impeller does turn and is still undamaged.* There's around 2500 hours on this engine.

So, my question is, Is it possible the pump gearing is slightly damaged and thus causing low flow?* Or is it more likely one of the heat exchangers is internally clogged?* Any suggestions for further troubleshooting?

Thanks in advance for any replies!

Have you check the though hull.* twice a year I have a diver clean/check the though hulls, running gear and zIncs.* Most under water though hulls have a grate over them that does not take much to restrict the flow.*

Yes, thats what I meant by intake.* Sorry if wrong terminology.* There was sea growth, and after cleaning it I was just sure the problem would be solved.**No such luck...* I am confident it is free flowing there, because I get free flow downstream of the strainer if I disconnect the hose.* Thanks for your reply.

Hard to say if the problem is caused by the oil coolers but it doesn't hurt to change them every 200 hours or so. If you don't know when they were last changed you should do it. Keep the old ones as spares if you think they are still good.

You could be collapsing the intake water hose at higer rpm. Did you check the hose for internal delamination that could be collapsing and reducing flow?

The strainer cap may be sucking air at a higer rpm. Use grease on the treads and make sure it is sealed well.

If the raw water pump is old, the cam might be worn and that will reduce flow.

There are a couple of possibilities

jleonard,

Thanks, I will check the strainer cap. hoses look good inside. Right now, there is minimal flow even at lower rpm. If we just start up cold the port engine sends good flow from the exhaust, but starboard is a trickle. We won't get up to higher rpm until we solve this problem.

There are some/all things to consider*to get*your decades old HX and cooling system back in good order:
<ul>[*]Replace all hoses[*]Clean strainers[*]Replace raw water impellers[*]Replace coolant[*]Remove HXs and take to a reputable shop for cleaning[*]Ridlime or similar product should be used to clean out system[*]Check exhaust elbows for wear[*]Insure exhaust hose is not plugged with growth or debris[*]Insure coolant and raw water pumps are not leaking at seals.[/list]
Do the same for your genset.*All of the above are considered normal maintenance on a boat. Go by the manuals for any other coolant system checks and maintenance.


-- Edited by sunchaser on Thursday 7th of July 2011 10:14:26 AM

The intake hose between the though hull and the water pumps has to be wire reinforced hose so it does not collapse as the pump is sucking.* The hose after the pump**does not have to be reinforced as the pump is blowing.* It sound like the heat exchnagers need to be cleaner/reamed/tested.*Over time most of the out side tubes will*plug*so the water flows only though the a few center tubes.*Most exchangers are a bundle of copper tubes and most marinas have a local radiator shop that can clean and test.*

Each time I start the engines are run to the sten to check the water flow.*

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If you cleaned out the debris from the heat exchanger but did not clean out the honeycomb of small tubes inside the exchanger, all of the other suggestions made will be good maintenance, but won't solve your problem. We posted the info on our website on one way to do this,

http://trawler-beach-house.blogspot.com/2009/09/servicing-cooling-system-on-our-ford.html

You can also pull the exchanger and take it to a radiator shop for cleaning if you are not comfortable with it. Hope this helps. Chuck

Fotoman wrote:
Hard to say if the problem is caused by the oil coolers but it doesn't hurt to change them every 200 hours or so. If you don't know when they were last changed you should do it. Keep the old ones as spares if you think they are still good.

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I think changing the oil and transmission coolers at every 200 hours would be expensive and time consuming. We did change ours at 1200 hours just because we were not sure how long they had been on the boat. The boat and engine are 30 years old so we figured it could not hurt. Chuck

Thanks all for the great suggestions. Does anyone have experience witha Jabsco pump failure, specifically, do they fail catastrophically or just become less effecient?

fshrcutb8 wrote:
Thanks all for the great suggestions. Does anyone have experience witha Jabsco pump failure, specifically, do they fail catastrophically or just become less effecient?

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*Fishrcutb8---* We have Ford Lehman 120s in our boat which are essentially the same as the engines you have but with two more cylinders.* The stock Lehman raw water pump setup on* the FL120*consists of a Lehman-designed drive coupler with an off-the-shelf Jabsco impeller pump on the end of it.* Their are several things that can cause the Jabsco pump to fail outright or reduce its waterflow.* If the impeller fails, no water will be moved.* So that's the "catastrophic" failure.

There is also a gradual "failure."* The pump has a wear plate behind the impeller and a cover plate in front of it.* Both of these plates wear over time from the friction of the impeller.* As the plates wear the fit between the plates and the impeller loosens up and the impeller starts losing"compression."* This will reduce the waterflow.* The cure is to install a new wear plate and cover plate.* At the same time this is done it's also a good idea to replace the seal on the impeller drive shaft.* A trick diesel mechanics sometimes*do on pumps that allow this is to simply flip the cover plate over, which puts the worn side out and the smooth side in.* So you get twice the time out of the cover plate.

If your pump impeller is turning properly and the impeller is the correct size and shape for the pump, I would suggest perhaps overhauling the pump with a new wear plate, cover plate (or flip the one that's there), and shaft seal.* The impeller has to be a very tight fit against both the wear plate and cover plate in order to move water properly.

The Johnson pump you refer to is the way to eliminate the eventual catastrophic failure of the Lehman raw water pump drive coupler, which has a fatal flaw in its design.* The Johnson pump eliminates this drive coupler altogether.** They can be fitted to FL120s and FL135s.* The FL120 normally takes the 3/4" pump while the FL135 has to use the the 1" pump.* HOwever the 1" pump fits the FL120 very nicely so some people--- including us--- put the 1" pump on the FL120 for a slightly higher water flow.

I don't know if the four cylinder Ford Lehman can be fitted with a Johnson pump.* The people to ask are American Diesel.* The founder of American Diesel, Bob Smith, designed some of the mariniztion components for varioius Lehman conversions*way back when, including the FL120's*raw water pump drive coupler (which he says today is a less than ideal design).* He or his son Brian can tell you anything you want to know about Lehman engines and they also supply parts.


-- Edited by Marin on Thursday 7th of July 2011 09:06:53 PM

Hi fshcutb8
I didn't see anyone mention it, but here is a couple of real simple tests that may help you find the problem.
1. With the engine off, squeeze the raw water rubber hoses with your hands and note the softness of the hose.* Then start the engine and squeeze them again and note if the hoses get overly hard or may even seem to swell up with pressure.* If so, your pump is working fine, but you have a restriction somewhere in the water cooling system.* If you have a low place where salt water sits when the engines are off, salt/silt may have deposited and reduced the pipe size to as thin as a pencil.* It may be in a metal pipe, so check inside them closely. This happen more often than you think, especially if the engines sit for long periods of time without running.*
2.* Sounds like you have checked the coolers thoroughly and good advice about rebuilding the pumps.* But how about your exhaust manifolds and risers?* They too need to be checked and cleaned every so often.* Exhaust heat and salt water cause exposed cast iron to form iron oxides and excretions which will build up and restrict passage ways and water flow. Shocking how quickly this can happen. *Open them up and remove any loose excretions or blockage. *I've seem quarter sized excretions which laid loose in the exhaust manifold and when the engine was started would wash up and partially block the water outlet.*
Don't take anything for granite, check it all until you find the problem. *It's there somewhere, just a process of elimination.
Good Luck
Larry B



-- Edited by Edelweiss on Thursday 7th of July 2011 09:05:24 PM


-- Edited by Edelweiss on Thursday 7th of July 2011 09:06:14 PM