Engine overheat despite all new water intake system
- Thread starter Ward H
- Start date
I believe I found the reason for that seaweed clogging my raw water intake.
The dual sized hose barb, as stated before was made so either 1/2" or 5/8" hose could fit on the barb. The other end was 1/2" NPT thread with 1/2" ID.
Turns out the 1/2" hose barb portion ID was only about .312". After cutting off the 1/2" hose barb portion the ID of the 5/8" was about .420". Since the threaded end was a full 1/2" ID, I bored out the 5/8" hose barb end to 1/2" ID.
The new 5/8" hose barb with 1/2"NPT thread had a slightly smaller ID of .402". That was the reasoning beyond boring out the original fittings to .50".
Who would have thought that different manufacture fittings would have different IDs.
In both photos the dual sized hose barb is on the left and the single 5/8" hose barb is on the right.
I do have a 3/4" thru hull I can use so I'm going to follow the recommendations to change to the 3/4" thru hull and valve. I'll go with 3/4" straight hose barb, 3/4" hose and a 3/4" 90 degree full flow elbow into the raw water strainer. That should help any foreign material to end up in the strainer instead of clogging inside the hose or at the fitting.
Many thanks to everyone!
The dual sized hose barb, as stated before was made so either 1/2" or 5/8" hose could fit on the barb. The other end was 1/2" NPT thread with 1/2" ID.
Turns out the 1/2" hose barb portion ID was only about .312". After cutting off the 1/2" hose barb portion the ID of the 5/8" was about .420". Since the threaded end was a full 1/2" ID, I bored out the 5/8" hose barb end to 1/2" ID.
The new 5/8" hose barb with 1/2"NPT thread had a slightly smaller ID of .402". That was the reasoning beyond boring out the original fittings to .50".
Who would have thought that different manufacture fittings would have different IDs.
In both photos the dual sized hose barb is on the left and the single 5/8" hose barb is on the right.
I do have a 3/4" thru hull I can use so I'm going to follow the recommendations to change to the 3/4" thru hull and valve. I'll go with 3/4" straight hose barb, 3/4" hose and a 3/4" 90 degree full flow elbow into the raw water strainer. That should help any foreign material to end up in the strainer instead of clogging inside the hose or at the fitting.
Many thanks to everyone!
Brilliant! I used this technique yesterday, and it worked perfectly. Thank you!
Here's my situation. I'm moored in a tidal river, the Westport, East Branch. When it ebbs, tons of grass comes down, a lot on the surface. For 17 years with a Catalina 36, with a screen on the outside of the through-hull, I almost never picked up anything in the raw water input. Cleaned the strainer annually.
Now I have a Tartan 3800; no screen on the hull, and a Groco strainer. I can pack that strainer with grass, and sometimes small fish, in a couple of days. Yesterday the exhaust water flow diminished and I had steam while charging batts at 1,500 RPM. Cleaned the strainer, which was packed. Still no good. The through-hull goes immediately into a sharp elbow, then ball valve, then the hose to the strainer. No clearance for a sweep instead of the 90º elbow. I closed the seacock and took the hose off the strainer. Opened the seacock, only a dribble. Got the airhorn - one good blast and it was clear! Made a very satisfying burp-bubble sound. Now had a fountain of water from the hose.
Thank you again! And, despite what some say about screens, there are situations where they really, really work.
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.
Many commercial boats have just that. Called "keel coolers", they're like a long skinny radiator or a series of pipes on the outside of the hull that the coolant travels through and dissipates it's heat to the sea. Very simple and reliable, and the engine only needs the one pump. Really no different than the radiator in a car. Never heard of one on a sailboat though, as they they do add considerable water resistance.
Many commercial boats have just that. Called "keel coolers", they're like a long skinny radiator or a series of pipes on the outside of the hull that the coolant travels through and dissipates it's heat to the sea. Very simple and reliable, and the engine only needs the one pump. Really no different than the radiator in a car. Never heard of one on a sailboat though, as they they do add considerable water resistance.
The HX on the Beta appears to be smaller than the Universal so that may be why they spec a larger supply line.
I've been using them for years. I find that weed (here we have Eurasian Milfoil which is an insideous invasive species) will be deflected by the external strainer and never get to the internal one. If using the scoop type one, face the scoop aft, not forward. That helps deflect the material. They do get zebra mussels inside that you have to remove the scoop to get to, but here (Michigan) we have to haul out for half the year so that's not a big deal.
Universal originally used a two inch diameter heat exchanger. A service bulletin later recommended increasing it to a 3 inch diameter HX. Apparently the 2 inch unit was undersized for the motor in warmer water regions. In increasing the diameter of the HX they did not change the pump size or the size of the supply feed. The Beta HX might be shorter but it appears to be a larger diameter and the pump looks to be larger than the Oberdorfer, they are using a Johnson pump. Heat removal is partly a function of flow rate.
True, I agree; I'd say it's a strong function of flow rate, along with the amount of heat to be removed, HX characteristics, ambient air temp (around engine), seawater temp. I used to know the math for keeping semiconductors cool, maybe someone hear can school us on marine inboard engine cooling!
I'm seriously considering a raw water flow sensor, and also the Noland RS-11 engine sensor to NMEA2000 device.
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I suggest you pick up Don Casey’s book This Old Boat. It is a great source of edited, quality advice/instruction from someone who is very experienced. There’s a chapter all about intake through hills and strainers/filters/pumps. No affiliation, it’s just a good book for the DIY’er.
I personally like external strainers, in one spot where I sail we have lots of moon jellys and rafts of sea grass; never had one clog in the 35 years that I’ve had a boat with one - and since I said that I’ll get a clog tomorrow for sure.
Granted I clean them every year when I haul out and our season is short in both spots where we have a boat. I’m sure things are different for those who stay in all year.
FWIW Don Casey recommends an external strainer on intake through hulls, just don’t neglect them or let someone paint over the holes.
I personally like external strainers, in one spot where I sail we have lots of moon jellys and rafts of sea grass; never had one clog in the 35 years that I’ve had a boat with one - and since I said that I’ll get a clog tomorrow for sure.
Granted I clean them every year when I haul out and our season is short in both spots where we have a boat. I’m sure things are different for those who stay in all year.FWIW Don Casey recommends an external strainer on intake through hulls, just don’t neglect them or let someone paint over the holes.
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