Engine overheat despite all new water intake system

Ward H

.
Nov 7, 2011
3,645
Catalina 30 Mk II Barnegat, NJ
One of my winter projects was new thru hulls, valves and a nice new Groco bronze raw water strainer. The strainer replace the OEM plastic Sherwood strainer.
On the C30 the intake thru hull is 1/2" with 5/8" hose to the raw water pump. The Groco has 1/2" intake ports so I bought Groco bronze hose barbs with 1/2" threads and the barb would accept 1/2" and 5/8" hose.

Splashed the boat and no leaks, as expected. Motor ran well and stayed at 160 deg as is normal for about the 3 hours I've run it since launch.
I went for a sail Friday evening and as the sun was setting I dropped sail near our channel and headed back in. After motoring about 5 minutes and just after I entered our channel I heard the faint sound of an alarm. It took a minute to realize it was coming from my boat, then identify it was coming from the engine panel. I still had my sunglasses on and it was dark enough I couldn't read the panel gauges. My first thought was oil pressure but then I noticed the exhaust sounded different. Looked and sure enough only steam was coming out of the exhaust.
My options were:
Limp back to slip which was about 1/4 mile away, risking the engine.
Cut motor and drift into a fishing pier before I could get fenders and lines out
Cut the motor with enough momentum to steer across the narrow channel and drop anchor which is what I did.

Since it was now dark I decided to call for a tow and figure it out back in the slip.

Pulled the cover of the pump and the impeller was in good shape and the pump had some water in it. Pulled the strainer screen out and it was completely clean.
Pulled the hose off the intake side of the strainer and found this:
Intake Clog.jpeg
A clog of grass.
Since the barb is sized for 1/2" hose, then gets thicker to take a 5/8" hose, the ID of the barb must be less than 1/2".
I think my mistake was using the combo barb fitting and I would get more flow and less chance of a clog at that fitting with a true 5/8" hose barb fitting.
I now have on order a couple of true 5/8" hose barbed fittings.

Now on my project list are new gauges with better lighting with visual as well as audible alarms.
 
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Apr 8, 2010
1,942
Ericson Yachts Olson 34 28400 Portland OR
For your next haul out, consider changing the thru hull to a 3/4 inch. Those old half inch ones are indeed easily clogged.
 
Sep 3, 2013
38
Beneteau 331 Brewer's Warwick
While you were changing things did you forget to re-install the strainer on the outside of the hull?
 
Oct 22, 2014
20,995
CAL 35 Cruiser #21 moored EVERETT WA
That looks like a healthy gob of seaweed.

I have tried to avoid the multi size fittings and the 90 degree less expensive turns. Pay the extra and get the full flow bends. Also go with the 3/4 inch thru hull if possible. Water to the engine in volume is better than none.
 
Apr 8, 2010
1,942
Ericson Yachts Olson 34 28400 Portland OR
While you were changing things did you forget to re-install the strainer on the outside of the hull?
Some folks like those, but IMHO please do not put one of those on. It collects weed and critters and the only way to clear it is to dive in. Better to be able to clean the strainer screen inside of the boat.
 
Jan 19, 2010
12,362
Hobie 16 & Rhodes 22 Skeeter Charleston
That was well written and easy to imagine the layout. I like to read about other people's diesel issues since I don't know much about diesel engines.

The largest sailboat I've ever owned was a Balboa 26 and the largest sailboat I've ever chartered was a Ranger 29... and even the Ranger had an after market O.B. installed. So I've never had a diesel. Stories like this are one of the reasons I find diesels scary. In any given week there will be a story about water in the tank, or bacteria in the tank, (tank polishing) or a fuel line that needs bleeding, glow plugs that won't glow, or seleniods that wont solenoid and.....

I know gas O.B.'s have their problems... so I guess it is the devil you. But I can't help but wonder if a better system could be developed. What are the common denominators when it comes to diesel problems and what would be the engineering solution to avoid those problems?
 
Oct 22, 2014
20,995
CAL 35 Cruiser #21 moored EVERETT WA
@rgranger Diesel engines sound scary but they really are simple machines.

I was more concerned about the Atomic 4 gas engine I worked on then the diesel I learned to maintain. Power to fuel weight ratio is excellent for a boat. They just need air, fuel, and compression to run.

Love the diesel.
 
Sep 25, 2008
957
Macgregor & Island Packet VENTURE 25 & IP-38 NORTH EAST, MD
Cut the 1/2" part of your barb off with a hacksaw, then you will have a 5/8" fitting. I've done it afew times with those "combo" fittings.
 
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May 17, 2004
5,031
Beneteau Oceanis 37 Havre de Grace
That was well written and easy to imagine the layout. I like to read about other people's diesel issues since I don't know much about diesel engines.

The largest sailboat I've ever owned was a Balboa 26 and the largest sailboat I've ever chartered was a Ranger 29... and even the Ranger had an after market O.B. installed. So I've never had a diesel. Stories like this are one of the reasons I find diesels scary. In any given week there will be a story about water in the tank, or bacteria in the tank, (tank polishing) or a fuel line that needs bleeding, glow plugs that won't glow, or seleniods that wont solenoid and.....

I know gas O.B.'s have their problems... so I guess it is the devil you. But I can't help but wonder if a better system could be developed. What are the common denominators when it comes to diesel problems and what would be the engineering solution to avoid those problems?
I'm sure this could be debated nearly as much as anchor types, but I'm on the side of preferring diesels. The way I see it a gas engine is vulnerable to pretty much all the same risks, plus the potential for ignition / spark problems, and the slightly higher risk of explosion. A story like Ward's is just because of a clogged cooling water line, which is no less likely on a gas engine than diesel. Maybe your concern is more with inboards vs outboards than diesel vs gas. In that case I'd agree that an outboard is relatively simple, but on a larger boat brings its own issues with things like how to keep the prop in the water on a bouncing boat.
 
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Jan 19, 2010
12,362
Hobie 16 & Rhodes 22 Skeeter Charleston
@rgranger Diesel engines sound scary but they really are simple machines.

I was more concerned about the Atomic 4 gas engine I worked on then the diesel I learned to maintain. Power to fuel weight ratio is excellent for a boat. They just need air, fuel, and compression to run.

Love the diesel.
Good to know...
 
Jan 19, 2010
12,362
Hobie 16 & Rhodes 22 Skeeter Charleston
... A story like Ward's is just because of a clogged cooling water line, which is no less likely on a gas engine than diesel.
YES! And that gets to my point about designing a better system. I'm not an engineer so I feel like I'm speaking above my weight class a little but... at one point in the past I owned a 4-stroke AIR COOLED O.B. made by Briggs & Stratton. They no longer make them but I wish I had kept that engine. There was zero risk of a water pump failure or sucking up muck. So I can't help but wonder if we could design a better system. I can imagine a set of SS heat exchange coils glassed into the bottom of the hull. Or some sort of air cooled system that exits out the transom .... You would need a blower but at least no risk of sucking up seaweed. I'm just noodling ....

Maybe your concern is more with inboards vs outboards than diesel vs gas.
Yes! You are probably correct. I've never had an inboard and I like being able to just pull my O.B. and take it to the shop to work on. Maybe if I ever own a bigger boat I'll know.
 
Jan 27, 2008
3,045
ODay 35 Beaufort, NC
That was well written and easy to imagine the layout. I like to read about other people's diesel issues since I don't know much about diesel engines.
I know gas O.B.'s have their problems... so I guess it is the devil you. But I can't help but wonder if a better system could be developed. What are the common denominators when it comes to diesel problems and what would be the engineering solution to avoid those problems?
A friend of mine built a steam powered boat. It had a wood fired boiler and a steam engine. All you needed to do to fill it up and run it was get some wood, fill it with water, start a fire and go until you ran out of wood.
 
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Ward H

.
Nov 7, 2011
3,645
Catalina 30 Mk II Barnegat, NJ
I've never had an inboard and I like being able to just pull my O.B. and take it to the shop to work on. Maybe if I ever own a bigger boat I'll know.
I enjoyed having a boat with simpler systems including an OB. When it was time to move up to a bigger boat with multiple systems it was a sharp learning curve.
Having problems like this one is part of the learning curve. I think it is ironic that for all the planning, research and thought I put into upgrading the intake system that I got burnt by dual sized hose barb.

While you were changing things did you forget to re-install the strainer on the outside of the hull?
No external strainer for the reasons stated by @FastOlson.

Pay the extra and get the full flow bends.
I couldn't find full flow bends with 5/8" barb and 1/2" thread to fit the Groco. You had mentioned this before so I did go with a 45 deg street elbow to ease the bend. That was needed for clearance.

Cut the 1/2" part of your barb off with a hacksaw, then you will have a 5/8" fitting. I've done it afew times with those "combo" fittings.
That was my first thought but while I was checking for a blockage further into the fitting, it felt like the ID did not get larger where the OD expanded to 5/8".
If I didn't find a 5/8" barb with 1/2" thread I would give that a try.

For your next haul out, consider changing the thru hull to a 3/4 inch.
I may just do that. Another option is to use the 3/4" macerator discharge thru hull which is now a spare.

A question for the board. If I switch to a 3/4" thru hull, valve and hose I'll need to switch to a new strainer with 3/4" intakes, correct? If not, I will still have a 1/2" restriction at the strainer intake.

Thanks

PS: I think I need to also focus on a better engine temp alarm. The existing one can barely be heard with the engine running and the gauges are not readable in the dark. That is a subject in another thread.
 
Jan 19, 2010
12,362
Hobie 16 & Rhodes 22 Skeeter Charleston
When it was time to move up to a bigger boat with multiple systems it was a sharp learning curve.
Did you just dive into manuals or did you take some classes? If you were doing it again, would you make the same choices w.r.t. climbing that curve?
 

Ward H

.
Nov 7, 2011
3,645
Catalina 30 Mk II Barnegat, NJ
No classes. I studied Maine Sail's marinehowto.com web site, his section here on SBO, read every thread in the C30 section here on SBO and asked a lot of questions, no matter how stupid I felt, here on SBO.
Back in my teens and 20s I rebuilt a few cars and an engine.
Basically I've spent a lot of evenings and winter days reading threads and saving notes when the threads apply to a system I need to work on.
 
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Oct 22, 2014
20,995
CAL 35 Cruiser #21 moored EVERETT WA
I see. You can get 1/2 NPT to 3/4 but not 5/8. Wonder what would happen if you used 3/4 for the hose and found a 3/4 to 5/8 straight barb fitting.
 

Ward H

.
Nov 7, 2011
3,645
Catalina 30 Mk II Barnegat, NJ
I see. You can get 1/2 NPT to 3/4 but not 5/8. Wonder what would happen if you used 3/4 for the hose and found a 3/4 to 5/8 straight barb fitting.
Switching to my 3/4" thru hull/valve with 3/4" hose to a 3/4" barb-1/2"NPT fitting at the strainer will at least put the restriction at the strainer which gives me easier access if the restriction causes another flow issue.
Next time at the boat I'll have to see what I need to route the hose from the larger thru hull to the strainer.

In the meantime I'll replace that dual sized barb to the 5/8" barb I have coming from FS.