Perpetually sticking valves/low power

[Jyrome]

I have an early model, raw water cooled A4 in a 1955 15' Hinckley Kingfisher runabout. The cylinders and valves were rebuilt less than 100 hours ago. Being as this restoration is a work in progress, I have been picking away at other issues than the engine.

The engine starts great and idles very smoothly. If I leave the boat unattended for more than a couple of weeks, the valves stick on at least 2-3 cylinders, intake and exhaust valves. I did not check the compression right after the re-build but after I freed the valves the last time the compression was low on all four cylinders (80 p.s.i). I have not had a chance to check compression after some hours of running and blowing the crud out. I do mix MMO into the fuel.

The plugs have shown a bit of rust on them. Running the engine up in the yard this summer, the manifold showed some water leakage on the outside. I tightened the manifold and flushed the oil and that took care of the external leak. There is currently no water in the oil pan.

The mixing point for the sea water into the exhaust is close to the engine, about 8", so I will look at moving that lower and farther away, should steam be returning to the valve chambers. I do not have a water lift muffler as the exit point is 12-14" below the exhaust output.

I have had concern that the engine is not operating at full power as well. I have reduce the prop to a 10/6 three blade with a fairly flat pitch and rather narrow blade surfaces. The engine still tops out at about 2200 rpm/6 knots under load. It easily runs up to 3500 with no load. The tach is accurate. Bypassing the muffler for testing raised the RPM by 100.

I see that most of you are cruising much larger and heavier boats at 2000 rpm and getting 5-6 knots. My gut feeling is that I should be getting better performance out of this fairly light, hard chined hull.

I will pull the engine this fall and check the valve guides for clearance, valve seating and tappet gap and replacement springs from Moyer, as well as moving the sea water mixing point and checking exhaust back pressure.

I'm probably on the right track with this program but I would welcome any further insights that are offered.

Thanks in advance for your comments.

[keelcooler]

Jyrome, Is the boat left in the water? With out a water trap you may get some moisture up the exhaust. In a slip you may receive some transom wave splashing running up your exhaust that exits near water line. If you trailer launch water might be getting up the exhaust even if you have surge flapper protection.

Is there an exhaust riser of any kind?

[67c&ccorv]

Originally Posted by Jyrome

I have an early model, raw water cooled A4 in a 1955 15' Hinckley Kingfisher runabout. The cylinders and valves were rebuilt less than 100 hours ago.

I have had concern that the engine is not operating at full power as well. I have reduce the prop to a 10/6 three blade with a fairly flat pitch and rather narrow blade surfaces. The engine still tops out at about 2200 rpm/6 knots under load. It easily runs up to 3500 with no load. The tach is accurate. Bypassing the muffler for testing raised the RPM by 100.

I see that most of you are cruising much larger and heavier boats at 2000 rpm and getting 5-6 knots. My gut feeling is that I should be getting better performance out of this fairly light, hard chined hull.

(Try an Indigo 3-blade if you have the money.)

I will pull the engine this fall and check the valve guides for clearance, valve seating and tappet gap and replacement springs from Moyer, as well as moving the sea water mixing point and checking exhaust back pressure.

I'm probably on the right track with this program but I would welcome any further insights that are offered.

Thanks in advance for your comments.

I think you have anwered your own question(s).

[Jyrome]

Thank you all for you comments, I really want to look at this from all angles before I pull the head.

There is no water trap in the exhaust system or a surge flapper on the exhaust thru hull. Yes it did get left in the water this year, although it had been trailered the last two seasons.

This is a tiny launch and there is barely enough room in the engine box for the existing exhaust system. It does raise an interesting point however, if the exhaust system is full of seawater at shut down, I could see where sloshing could allow significant moisture back into the manifold. I have had sticking on the exhaust and intake valves, I can't get my head around the sloshing causing the intake valves to stick unless it was really lapping in there. There could be multiple issues.

It would be simple enough to close the seawater inlet valve a couple of minutes prior to shut down and install an exhaust flapper.

I have read the positive reviews about the Indigo 3 blade prop and I am completely open to playing with different props to get this boat just right. I need to solve the valve sticking issue and get the engine into a higher compression range before I drop the money on another prop. The current prop is the same diameter with less pitch than the Indigo. Certainly there are more parameters to consider on prop design but I think I am in the "very close" range.

The A4 is what Hinckley shipped these center console boats with in the 50s. I have a copy of the original brochure which states "Delivers speed up to 15mph". I am skeptical that I will ever get that kind of performance, but surely the engine would have to be at absolute peak performance to approach that.

The boat had a 9/8 prop with it when we pulled it off the burn pile for rescue but I cannot be sure of the provenance of the prop as original equipment.

Jyrome

[keelcooler]

Jyrome, You should have your water injection no less than 4" below the exhaust flange level. Then down hill to exhaust without sagging.

To keep water from backing up the exhaust when launching and in the slip with a following sea, you can install a wooden plug. Years ago many yard mechanics installed exhaust plugs during lay-up and applied oils in the combustion chambers.Plugging exhaust, I was told cut down on moisture and stuck valve problems.

The old wood runabouts with a low profile often had nice plugs with eyelets and lanyards and when left in the water were inserted. I also remember some owners using balls.

You could also use an inline baffled muffler just before the transom that should help with a surge. That's if you have the room. An outside flapper of good construction would also help with a surge. The all rubber clamp on flappers are junk.

[Jyrome]

Thanks Keelcooler,

I do have an inline baffled muffler that I bypassed earlier this season as a quick way to asses whether of not it was creating excessive back pressure. By-passing the muffler increased the maximum RPM by 100 so I left it bypassed as there was not really much difference in sound. The seawater does quite a bit of muffling on its own.

Interestingly enough, the injection point is probably 3-4" below the exhaust flange so I could extend the hot section and lower that. The sole of the boat is pretty much at water line so 6-7' of exhaust hose and the muffler lie 3" below the exhaust thru hull (a big sag as it were). It is only under the aft thwart that there is room for the hose to rise to the thru hull, which is partly submerged anyway, making it quite easy for water to slosh back through the system. Its seems that leaving the muffler bypassed most likely did not help the situation.

I installed the exhaust thru hull in the original hole which I noticed was slightly below the water line on the first relaunching. I had forgotten all about that until you raised this point.

Thanks again,

Jyrome

[rigspelt]

Originally Posted by keelcooler

water injection no less than 4" below the exhaust flange level.

4" below the exhaust flange, or 4" below the highest point in the dry stack? I guess in some boat designs, those are the same thing?

[keelcooler]

Jyrome, A gallon of seawater sitting in that hose under the sun baked aft cockpit for two weeks might be the problem. Salt air,evaporation and condensation might allow a mild rust film to develop on your plugs and valves.

With 100 hrs on your rebuild your compression should be getting better , over 100 and not into the low 80's. Do some MMO burn offs. I think your 3 to 4 inches are OK in preventing injected water from splashing back up the dry pipe. As pictured with that motor cover, just no room for a riser.

You want that extra 100 RPM so you may decide not to install a flapper or muffler. May be a valve shut off just aft of the engine at the flex hose. Or use the plug and install a draining system at your low sag. Also shut the intake to prevent a back siphon.

I also wish for a 2400 RPM a4 w/a SS Indigo wheel. Something this sail-boater and power-boater agree on.

[Jyrome]

Thanks Keelcooler,

The symptoms of this season's failure fit that scenario exactly. I left the boat in fine starting/running condition. While I was away from the boat I had someone start it to put some charge on the battery. They reported that it started OK but ran rough. Checking the plugs, they reported rust on all four plugs. A couple of weeks later the engine was cranked a bunch and did not start and the seawater valve was open. Doh! From that point there was no compression on cylinders 2 and three. I immediately hauled the boat, freed the valves and change the plugs. Whammo, she started and ran fine. I flushed the oil, although it did not show any water in the oil, thankfully. That's where I left off.

I'll have the boat at home in a week or so and will get deeply into this. It has also made some ticking sounds after it warms up so I've got to inspect tappet gap and spring health. Hopefully I'll find the source of the lowered compression. I'll probably still have to pull the head to check the valve seating.

The Moyer Manual recommends pulling the studs prior to removing the head. Is this a necessary step?

Is it impossible to remove the head without removing the studs?

I don't want to cut corners, just not disassemble the motor farther than I have to.

Thanks,

Jyrome

[Marian Claire]

The head can be removed without pulling the studs. Be very very patient, tap tap pry, tap tap pry. Dan S/V Marian Claire