Still having power issues - Round two

[Jo Ross]

Jo Ross, sounds like you have two issues, over heating and lack of power.

The lack of water exiting the exhaust was probably due to "flow" causing the over heating not the heating evaporating the water. You will need to check the intake for flow and if it is clear then the pump, block restrictions etc..

The power loss could be many things. Since you pulled the plugs, what color were they. Were they white, sooty or an even brown? Fuel flow (pressure) can really be a big limiting factor as well as bad fuel. How long since your last tune up and what was done?

A dirty prop can really cause a loss of power and RPM's but should not cause a heating issue as with low power there is not much heat to dissipate and a hot engine can also loose power as it begins the seize .

Dave Neptune

Dave, I think you're 100% right after I did some more tinkering. Looks like the cap to my coolant pump is hemorrhaging coolant and needs a new gasket. I'll verify the impeller once I'm in there also. That has to be the coolant issue. I'll hit the carburetor with cleaner and double check compression today but the spark plugs looked as clean as when I put them in there when I pulled them out.
Also have a diver coming to clean the bottom and check the prop for fouling.

Can marine growth cause a "fouled prop"? I thought that was just fishing net or lines that could wrap a prop.

Thanks for the reponse!

[Dave Neptune]

Barnacles and crustations can cause big issues as they create drag as well as a disturbance to the water flowing over the prop. This creates both drag and cavitation increasing the load on the engine and not transferring the power to the water which drives the boat.

Re the cover if it leaks it also "sucks" air so the water is not moving through the pump efficiently at an approximate 700:1 ratio which is the air to water density ratio. IE the pump sucks air and not very much water with even a minor leak.

Cleaning the outside of the carb does little to clean the innards which also need a good blast of air to actually clean. Before cleaning the carb check fuel flow IE the filters. The only real check for fuel delivery is a "cheap" pressure gage. If the plugs had little color or were white it does indicate a lean condition and unless you know the carb is getting enough pressure cleaning is possibly a waste of time. A good color for plugs is light brown to brown. Dark brown to black is to rich.

Dave Neptune

[Oaktown27]

OK, I am back as I was waiting to to get the hull scraped and prop cleaned.

Went over yesterday, and the motor started right up, but unfortunately the power issue still exists. I did check the choke plate is wide open and the spark arrestor on the intake is clean.

When I did pull the plugs before, they were a bit black, which I think suggests to rich. I assume this would be a carb adjustment, but when there is no load the engine responds and powers up.

Could the stuffing box contribute to this?

Sort of at a loss, and am headed out on Thursday at 1/2 power.

Pete

[Dave Neptune]

If it is just an idle adjustment try opening the "idle air" screw a half of a turn to lean the idle. This is all that is adjustable. If it running rich beyond idle it is a problem inside the carb like a plugged air jet or float level to high.

A poor tune can also cause dark colored plugs. Have you checked for a good spark? Does the C-advance move freely? And have you moved the distributor which changes the timing and can also contribute to plug color.

Dave Neptune

[joe_db]

Do not tune anything until you check the prop though.

[Oaktown27]

Prop was cleaned during the hull cleaning last week. Interesting development yesterday. Looked at the distributor again to make sure the mechanical advance was free to move (is free and functioning), so adjusted the timing a bit both ways to see if there was a difference (there wasn't).

While I was testing in gear I had it maxed at ~1400 rpm, when it would suddenly jump to 2000 rpm. Prop and drive still turning. When I throttled back and tried to accelerate it would go above 1400. This happened several times.

Based on this I am now thinking the fuel system is the culprit. I know I thought it was running rich, so pulled a spark plug. Looking at this again, it is not terribly sooty.

Attached photo.

[Dave Neptune]

That is an extremely lean condition. The porcelain ( the white ceramic around the electrode) is what you "read" and no color means almost no fuel. The black on the edges of the body of the plug is not indicative of much of anything especially in a poor running engine. If you run it again try engaging the choke slowly while the engine is struggling in gear against the dock lines. If the engine speeds up for a few seconds check fuel pressure or delivery. Could be as simple as a clogged filter or a leak in the fuel line sucking air. A cheap pressure gage will save a lot of fussing around and gathering very little actual info. Do check the fuel connections to be sure they are not sucking air.

Dave Neptune

[Oaktown27]

Back at it, and installed a fuel pressure gage and checked for air leaks. Fuel pressure is a constant 3 psi (not under load).

I did take out the Gypsy Rose last week, and still couldn't get it above 1300 RPM, but was still moving.

In summary
Prop/Bottom scrapped/cleaned
Cleaned carb
Fuel pressure gauge and polishing filter
Fire order correct, and mechanical advance free to move
New plugs/points/coil

Guess maybe I just have to live with it. The only other thing I could think of is to rebuild the carb.

[Dave Neptune]

Two questions.

#1 Are your plugs still white?

#2 What are you doing when you "clean" the carb?

Rebuilding the carb is essentially disassembling cleaning and checking the float setting then putting it back together with a new gasket. The needle and seat is seldom replaced unless it is leaking and replacing the shaft seals should only be done by a pro or very skilled carb mechanic. This is what lead me to question #2.

Dave Neptune

[capnward]

It would be good if we were more specific about what is involved in cleaning or rebuilding the carb, and what the difference is. We A4 owners eventually become skilled in doing this. It should be expected as part of maintenance. I disassemble the carb every spring, clean it and remove the idle jet and maybe other jets, run a small wire around in the idle jet to remove any unnoticeable obstruction, put a bigger wire into the idle ports, check the spacing of the float, dress the float valve seat, and reinstall with new gaskets. I replace filters at the same time. I just call this cleaning the carb. Before I stopped using ethanol fuel I would get brown goo in the carb, requiring this annually if not oftener. Since then, I do it to be proactive, as dirty fuel is in my experience the commonest issue with these engines. To me, rebuilding the carb would be to do the above plus replace the jets, valves and nozzles with new ones. Usually not necessary.

[Oaktown27]

I did follow most of the process you outlined. I tore down the carb, cleaned the jets with a wire, cleaned the bowl, new gasket. Didn't adjust or check the spacing in the float. Perhaps this is something I missed?

Did not replace the jets or needle.

Going out again tomorrow, soe will see if the fuel pressure is constant under load.

[Jo Ross]

Two questions.

#1 Are your plugs still white?

#2 What are you doing when you "clean" the carb?

Rebuilding the carb is essentially disassembling cleaning and checking the float setting then putting it back together with a new gasket. The needle and seat is seldom replaced unless it is leaking and replacing the shaft seals should only be done by a pro or very skilled carb mechanic. This is what lead me to question #2.

Dave Neptune

How am I looking here?

I had the hull cleaned and checked for foul and while dirty it wasn't a foul and I'm still having capped power issues. I also pulled the carb and cleaned with carb cleaner through the jets. Still having the exact issue where my throttle only goes about half way with a change in response and the rest is just doing nothing. RPMs capped at around 1600 and when I did a pressure test on each cylinder I couldn't get any above 90psi.

[Dave Neptune]

The plug still looks to be running rich. Did you set the float?

1600 ~ 1800 is not uncommon on most A-4's with a direct drive. If you have the Indigo prop or a 2 blade with a 7~8" pitch you should reach 2200 with the 2 blade and 2400 plus with the Indigo if the engine is running well. My Volador with less compression than yours could get 2700 with the Indigo however I did a lot of fine tuning and carb work of which I am very experienced in doing.

You are missing something in the carb or ignition timing. I think you may have the float set to high which will run rich. I set mine 1/16" low and liked the gain in power.

Take along look at some posts on finding TDC and setting the timing, it really makes a difference in performance . If you still have points check the dwell as most of these old A-4's have very worn out distributor cams that can no longer be set by gap alone . That is a good reason to upgrade to an EI, once you do you will not look back and the "tune" will last for many years!

Dave Neptune

[Jo Ross]

Roger

I'll look at those things.

For my pressure drop, is there a thread I can look at that talks about the compression rings? I don't know what that actually means but I ran this thing extremely hot on my last outing and I'm worried I did some damage that needs attention.

[Dave Neptune]

Your compression numbers sound fine. No worries there.

How hot did it get? And are you raw water or HX cooled?

Dave Neptune