Tempermental old girl

[Baltimore Sailor]

My A4 is from 1975, and was rebuilt by MMI in 1993. I've mentioned my water pump impeller issues before in these forums, and my inability to find a replacement of the same height to give the same amount of "crush" by the back plate. I plan on replacing the water pump over this off-season, but until then I'm running on an at-least four year old impeller.

This season I've noticed the engine is running hotter. Whether it's just the weather in the Baltimore area (much hotter than last summer), or the impeller is finally giving up the ghost or I've got some water flow blockage in the engine I can't say, but even with my bypass valve closed all the way I am still rather warm.

Yesterday as I was motoring out of the creek at my usual cruising rpms of 1900 or so, I saw the temp gauge really starting to climb -- up over 190, pushing for the 100 C mark on the gauge. I knew this wouldn't do, so I throttled back to 1500 and the temps dropped back under 180 and stayed there until I hoisted sail. The odd part is what happened on the way back in.

There were thunderstorms approaching the area, so I dropped sail further out than usual and made a beeline for the marina. I pushed her back up to 1900, keeping an eye on the gauge, but it never went over 180 this time. I had noticed this behavior another time and wondered at it then. What would make the engine run cooler on the restart than on the initial start? It didn't appear that there was more water coming out of the exhaust either time.

[joe_db]

My engine has a 180 degree thermostat. When it starts hitting 190 I run vinegar through it. Seems the 180 setting causes salt to come out of solution and I need to get rid of it every year.
Also I had the temp go way high along with no water flow. That was cured by getting the fish out of the pump inlet.

[Dave Neptune]

Baltimore, I can think of two things right off. One it could be that you just sucked something like a plastic bag against the intake causing a temp spike, then it floated away while the engine was shut down or slowed. I have this problem from time to time as I sail in areas with a great deal of kelp.

The other is there could still be a piece of impeller or something else floating around in the system. I would suspect in the manifold at the exit port. Not a bad place to look when things start warming up in the lil beastie, it is the last and one of the most restricted areas in the cooling system as it tends to plug up over time.

I'd also consider finding the correct impeller or getting a new pump for self assurance.

Dave Neptune

[Mo]

I was thinking thermostat also. I had intermittent thermostat problems and finally removed the thermostat putting a ball valve on the hose leading into it. You might even want to try this for a test as I did. The thing with me is that it worked so well I left it there. The engine runs warm and I can run it hard in a sea. I can touch my fingers on the head without burning them with it wide open and that is my true test...regardless of what the guage says.

I live in Canada and the water is cooler here. That said, it is not like a car where the thermostat cuts flow to hold water in the rad. Might work for you.

[Jesse Delanoy]

I, too, have noticed higher operating temperature in the Baltimore vicinity of Chesapeake Bay over the past several weeks, although not climbing over 180. Prior to that, typical operating temp. at 1800 rpm has been 170 - 175.

My pump had developed a leak, so I just installed a new one the other night (long story about that). We'll see if that has an effect on the operating temp this weekend.

Jesse Delanoy
1977 Catalina 30
Off The Grid
Baltimore/Pasadena MD

[Baltimore Sailor]

@Jesse -- are you in the Pasadena area? Which marina? I'm at White Rocks, slip E23.

@Maurice -- I already have a ball valve in line before the thermostat. That's the "bypass valve" I mentioned in my OP.

The new water pump is already on the schedule. I can't find a properly "squishable" impeller to save my life, even after MMI sent me a replacement for the one I'd bought from them last season. I figure putting in a new pump is the best solution.

[Dave Neptune]

Baltimore, that is the best idea AND I would check at the exit fitting for the piece of mind. I check mine at the start of every season after the first start up and run.

Dave Neptune

[Baltimore Sailor]

Oh, a whole new exhaust run is on the schedule for the winter layover. The last rebuild was in '93, I have no maintenance records, and the guy I bought the boat from was NOT the mechanical type.

The side plate is coming off, the manifold, hot pipe run, the hose all the way back to the Venus lift muffler -- all coming off. New exhaust system for next year.

[Jesse Delanoy]

Baltimore:

We're at Hammock Island on the Bodkin