panioul

Hello. I perchased a modified zenoah 26 piston. I walbro 257, a copper Cylinder Gasket, a ZRC aluminum isolator block and NGK Iridium IX spark plug. I rebuild my engine and started it. I set the carb at 1 turn H and 2 turns L. The engine is starting easily and is reving very well outside water. The idle is very good and the acceleration the same. When I put it in the water it always goes about 10 meters and the engine dies even if the engine revs are high. I tried to increase the low and the high needles about half or 3/4 turn but the same think happened. I was running the engine outside the water with a water pump to cool it and it was running perfectly. Any ideas? Thank you very much.

Dockman

Try the lsn at 2 1/2.

MrMikeG

Rich runs
Lean dies

lolamon

Copper gasket is leaking, install a normal gasket or try tightening the head down after its gotten hot. Copper gaskets are known to be a headache. Make sure the isolator block is perfectly sealed too.

Hydro Junkie

Your description of what you did tells the story. By setting the carb to run good on the bench, you made it so it won't run on the water. As Dockman said, richen up the LSN and throw it on the water. If it runs at low speed, start tweeking the HSN. Setting a carb is a balancing act, each time you make a change, something else changes. Write down every change you make and the results. That way, if you need to ask for help, you can tell us what you did and the results.

panioul

Thank you very much for all your responses. I hope I will try it this weekend. I didn't try to open the low and the high speed needles too much because I knew that the factory settings are at 2 and 1 turn. Do you have any experience with a tuned engine and how was the needles set? I am just curius for how far should I go.

danielplace

Maybe just double check the new manifold and it's alignment of gaskets with the pulse port going through the manifold to be sure it isn't partially blocked somehow.

STEVE MARSHALL

Also check the fuel tank breather, if you have a full tank it doesn't take long to build up a vacume.

panioul

I have a fuel tank and I have an open hole at the cap to avoid a vacum. As far the gaskets from the manifold I will double check them but I am pretty sure that they are alligned correctly because before the rebuild of the engine I had found out that there was no hole at the factory flange for the pulse!!!! The symptoms then were totally different from the recent ones (I could not set a correct idle, the engine could not accelerate either at the bench or in the water etc). When I will try to richen up the needles is it possible to hold it inside the water and accelarating the engine (without freeing it) in order to check if the engine stops? It is very difficult for me to retreive it every time. At least to test the first results this way or the conclusions will be mistaken?

CraigHeidemann

You said it's a modified barrel, depending on the timings of the mod you may have to run smaller props / smaller pitch props. If it's to big it will run for a few meters then die, there is also a possibility one of your fuel lines could have a small cut and it's leaking air.

panioul

What about to try if it is switcing off while holding it inside the water? Of course it will be for a few seconds to avoid overheating but I think that I will have a first result if the setting of the needles are towards the right way

panioul

I have some good news! I tried it today. I opened the L needle at 2 3/4 and the H at 1 3/4. I put my finger on the carb to draw fuel and once it did it fired up immediately. I put the rear side in the water (to force resistance at the propeller) and it seemed that the engine was not quiting . I left it inside the water and I started doing circles. The throttle seemed that did not have response ( the servo was moving), so I took it out and close the H needle at 1 1/2. I fired it up again and put it in the water. At the second attempt everything was very good. It had very good throttle response and very very quick accelaration. The only drawback is that the top end is not very good but I think that I must be patient with this. I will first burn a couple of tanks and then I will try to close a little bit more the H needle.

Dockman

Glad to hear it.

panioul

I have one more question. What kind of prop or what diameter of prop would you suggest fot this kind of engine? The boat is a deep vee 41".

panioul

This weekend I had also my first tach test with a gps. The speed was 62km/h. The problem was that the engine was not getting "into" the pipe. I believe that my prop was to low inside the water and maybe the high end needle was too rich. I believe that there are still a lot of things to change!