Evinrude 50 (2-stk) Missing at WOT?

[pcmb]

have just discovered and joined this site – great place to share experiences and expertise. I also posted this on the Macgregor/venturer discussion board.

I own a 2006 Macgregor 26M and am very happy with it. It has an Evinrude 50 hp 2 stroke motor.
I live in Melbourne Australia

I wanted to see if anyone has had the following experience with this motor or other motors.

When the motor is at full throttle I notice that periodically it seems to hesitate (even a slight difference in engine noise) for a second. It is as if it has experienced an increase in resistance. The revs also drop fractionally when this happens. Some times this hesitation seems to happen quite often. It does not seem to happen at lower RPMs.

It has been back to shop twice and they cannot find anything wrong with the motor. Maybe it could be a cavitation
problem. Has anyone experience this and found ways to solve it?

Look forward to hearing from you

[delevi]

Sounds like the occasional air pockets or pockets of turbulant water, etc. I get this all the time, but it's something you feel/hear. It only lasts a split second... sort of a brief slip of the prop, which would affect engine RPMs and sound for that same brief moment. I don't think much could be done about it...would happen with any boat/motor. Not exactly sure if this is the same issue you're having. You wouldn't notice it under low RPMs, but 3/4-full throttle.

BTW, mine is an 05 w/ Etec 50.

Leon

[Lease]

Might be worth looking out the back for jellyfish carcasses during these events. Either that, or perhaps weed.

I would also be checking the location of the log paddlewheel (if fitted). If it is too close to the centreline, then it may be throwing back disturbed water.

In any event, it does sound more like these sorts of things than engine related. Most cavitation causes an increase in rpm and a decrease in power.

[pcmb]

Thanks for your input.

Another thought - How well should the petrol(gas) tank be vented?

My tank has a small screw for venting - I have just loosened this not removed it.

Unfortunately it will be 3 weeks before I can try this

What do you think?

Peter

[delevi]

Not familiar with that type. Some tanks have vent caps. Mine are self-venting when the intake hose nozzle is plugged in. When left on the trailer or in the slip for a while, I just crack open the fill caps to vent. I always have verything closed tight while under way, motor or sail. Some tanks are different, so perhaps someone else can chime in.

Leon

[c130king]

PCMB,

I have an 05 with 2-Stroke 40HP Mercury. I have also experienced the engine anomalies you have mentioned. I normally throttle back, look over the stern, see nothing out of the ordinary, and then continue on. Maybe this is a 2-Stroke issue. Seems like I experience it more when the water is more choppy. But it has only happened a few times.

As for the tank vent. My engine will shut down after a while if I don't have the vent open. The vent is a small screw opening on the top of the cap. Don't have to remove. To be honest, I hardly ever close this vent. Only for long-term storage. I don't worry about the small amount that evaporates.

Good luck,
Jim

[opie]

My Honda 50hp 4 stroke did the same thing. I replaced the gas hose fittings and bulb and it went away. In my case, some air was getting in the system. It was not enough to cause trouble at low speed but at high speed it caused the hesitation. Good luck with your motor...

[Terry]

I leave the vent open at all times now. The first few times I forgot to open the vent I went to switch tanks and found the one I was using completely collapsed now I keep it open.

[Don T]

Hello,
A drop in RPM could be current related. I get these on a regular basis in the San Juan Is. The curent there is quite turbulent causing changes in RPM and speed.
Engine related cause could be momentary lean mixture from fuel supply restriction / air in the line etc. Or charging system momentary load.

Good luck

[Harrison]

Thanks for your input.

Another thought - How well should the petrol(gas) tank be vented?

My tank has a small screw for venting - I have just loosened this not removed it.

Unfortunately it will be 3 weeks before I can try this

What do you think?

Peter

When running at WOT I have to open up the tank breather valve completely. I used to open it enough (what I thought) to allow air to get in the tank as the fuel was consumed but this was not enough. While running at WOT after a few minutes, she'd start to sputter, then finally die. I'd switch tanks, (thinking I had bad fuel, a clogged tube or something in the fitting) and she'd start right up. After replacing the pickup tube, the connection fittings, and many gallons of what I thought was "bad fuel" all to no avail, I started looking to something else. Ever since I decided to open up the valve "completely" I have NEVER had the problem return. I basically I chalked it up to the valve, even though it's open, mine rests on a rubber O ring, thus creating a seal. Tiny, but still a seal.

---Harrison

[BKAFER1]

If you think its a cavitation problem, one way to tell is to look at the prop.
If your starting to see little dings or pin pricks in the prop. meaning its not as smooth as it was. This can be a sign of cavitation. Air ( bubbles )getting under and into the prop area.

Then check the zincs. If they look ok. Its even more evidence of cavitation.

If your zincs and prop are both eaten then look for info on electrolsis.

[Catigale]

Let us know when you find your ignition problem

[pcmb]

Thanks again for all the input.

I will first check the venting of the fuel tanks - It will be a couple of weeks until I can get to the boat.

Will let you know how it goes

Peter

[Zoran]

For symptom like this you can have two possible problems, lack of fuel or no spark. I had the second one and discovered that my spark plug cable was damaged and sometimes will get closer to the motor cover, it was arching there instead on a spark plug. The other possibility is not enough fuel (check filters, possible hose leaks where air can get into the system, closed vent on the fuel tank.. etc).

Zoran