Is my mechanic right?

[jsalz]

Hello all,
We bought a 74 Johnson 50hp (50ESL74M). Initially, the motor started and idled perfectly but bogged when we tried to reach WOT. Based on what I read here, and the manual, I thought it was the fuel pump as it was original. I replaced the fuel pump and took apart the carbs and they looked clean and undamaged. I did not adjust the floats. The inlet needle valve and seat looked new also. Anyway, we took the boat out again and it did basically the same thing. Bogged when trying to get to WOT but this time it idled very fast. We took the boat out of the water again and brought it to the shop that the previous owner had used for years.
The mechanic called me today and said that the Low Speed Needle Valves were wide open and that they were missing the retainers. So he dialed the needle valves in, put on the retainers and put it in a test tank. He said the boat rev'd right up using the control box and he thinks that is all that was wrong and by the way, that'll be 175 bucks.
Now for the questions. I cut and pasted the part of the manual into this post. Why do I not see the retainers he is referring to. The other question is, if the Low Speed needle was wide open, would that affect trying to get to WOT and higher RPM's. I am pretty new at this, but I thought that would only affect the idle speed?
Is it possible the previous owner adjusted the motor to compensate for a faulty fuel pump?
Thanks for looking...

 

[ezeke]

Re: Is my mechanic right?

I'm not sure what he was calling a retainer, possibly the packing.

You can't compensate for a fuel pump because all it does is fill the float bowl. Once fuel is in the bowl, the pistons take over and pull the fuel mix through the carburetors. When you close the choke plates, it blocks the air and increases the amount of fuel and the fuel/air ratio being sucked into the engine.

Edit: See Jimmbo's entry #15 below; if the fuel pump membrane ruptured, allowing fuel to flow into the pulse cylinder, it is a possible cause for the incorrect adjustment having been made.

 

[jsalz]

Re: Is my mechanic right?

Ok, that makes sense. Do you think that the low speed needle could affect high speed performance. Is it possible for the low speed needle to flood the motor at WOT?

 

[tashasdaddy]

Re: Is my mechanic right?

with the packing missing, it would suck air. you also have the high speed jet in behind the drain plug in the front of the bowl, could have been dirty.

 

[TommyA]

Re: Is my mechanic right?

First question I have never seen a retainer for a idle needle valve screw with the possible exception of lawn mower engines and judging on the picture provided there isn't on for this engine. Second Yes I believe that the idle screw was adjusted out to compensate for the fuel pump. The idle needle valve screw does not affect the wide open throttle so there is something else causing problems. Think of it as two separate processes with a slight area in the middle where your idle jet and the high speed jet provide fuel to the engine at the same time. At wot you should just use the high speed jet only. There could be several things that cause problems with wot but first I would clean the carbs to eliminate them.

 

[mikesea]

Re: Is my mechanic right?

simply yes,one could effect the other,i also believe he was reffering to the packing,and if the eng.is running good,the mechanic was right,the 175 seems fair enough these days,they are getting 90-th 100 an hr in the fl keys plus parts and travel time if mobile

 

[TommyA]

Re: Is my mechanic right?

After a second thought my statement that the idle valve didn't supply fuel at wot may be wrong in some cases. Carburetor design would give the answer to that. In most cases the idle and the high speed are two different systems. Normally the throttle plate closed will cause fuel to be sucked out of the Idle passage and the opening of the plate causes fuel to draw from the high speed passage. This is all part of the venturi principles.

 

[jsalz]

Re: Is my mechanic right?

Thanks for the replies. My problem is, I gave the mechanic a detailed scenario of what was happening. I was just kidding about the cost. It just seems he did not look very hard for the source of the problem. I am concerned there maybe something else wrong and he found one of the problems and said, that oughta fix er.
Anyway, it seems weird that the mechanic told us that the LS needle was basically flooding the engine and then I read here that if it was wide open, it would be sucking air. By the way, he didn't even look at the carbs. Guess we'll have to try it out and see. Last question, is running the motor in a test tank a good indicator of how it will run under load? The weight of the boat and two fat fisherman seems to be missing from the test.

 

[dimock44]

Re: Is my mechanic right?

Why not just ask the mechanic to show you the Part and where it went. A good mechanic will be glad to. As far as the price goes you pretty much have no choice. Get to know the people at the shop and you will soon get a feel for whether or not to trust them. Get an oem manual and do some reading even if you don't do the work you will know what there talking about

 

[tashasdaddy]

Re: Is my mechanic right?

if he put a test prop on it, it would be fairly accurate, just your prop maybe. too many variables.

 

[jonesg]

Re: Is my mechanic right?

On many 2 stroke engines I play with (not outbaords) the low speed needle can , if opened too much, flood the intake with fuel, then when the throttle is opened the fuel gets kicked up into the cylinder and floods it out.

Will an outboard do the same thing?

 

[ottertail]

Re: Is my mechanic right?

In a post a little ways up I am in need of a clarification from tommy. How can adjusting the low speed needles compensate for a fuel pump issue? Can some one shed light on this for me and the other readers?

 

[TommyA]

Re: Is my mechanic right?

The increased opening of the idle screw allow the engine to pull additional fuel through the idle jet. Thus solving a idle problem the first owner was probably having. When the fuel pump was rebuilt there was a better supply of fuel to the carburetors thus causing a faster idle. This was problem 1.

Problem 2 is the bogging down of the engine at attempts to WOT. My first attempts to fix this would be to check the high speed jets because at WOT fuel is pulled mainly from it.

Carburetors have two sides in operation. Idle side that operates at lower to medium speeds and the high speed side that begins to operate at medium and takes over at higher speed.

 

[Xcusme]

Re: Is my mechanic right?

I disagree on the rebuilt fuel pump being the reason for a faster (or different) idle speed. The fuel pumps job is to supply fuel to the carb. The carbs float needle controls the amount of fuel that enters the carb, regardless of pressure, except it would take less time to replace the used fuel in the carb, if the pressure was slightly increased by a rebuild. The low speed needle valve would control only the idle fuel to air mixture ratio and thus low speed rpm's.

 

[jimmbo]

Re: Is my mechanic right?

Perhaps the retainers the mechanic was refering to were the nuts used to tighten the packing. As for the fuel pump, the old one might have had ruptured diaphram. That can give conflicting rich/lean symtoms, one cylinder running rich while the others on a multi cylinder engine running lean. Since most 2 stroke outboard carburators do not have accelerator pumps, the off-idle curcuit is usualy set up rich so as to prevent bogging upon accelleration.

 

[TommyA]

Re: Is my mechanic right?

I believe that the key to this idle speed situation is in the fuel level in the float bowl of the carburetor. Before the rebuild the weak fuel pump was more than likely barely keeping up with the fuel amount needed to run the engine. Remember the engine sucks fuel from the carburetor it is not pressured through. With the lower fuel level, opening the idle needle orifice reduce the restriction allowing the engine to suck enough fuel for the idle circuit. The wider idle orifice compensated for the lower fuel level.Once the rebuild was accomplished the fuel level returned to the upper level where it was normal. At this point the wider idle orifice allow more fuel at idle thus increasing the idle speed. The higher fuel level in the carb requires less energy to pull fuel from the bowl thus requiring more restriction in idle circuit to limit fuel amount. To correct that the mechanic reduce the orifice to its normal setting to reduce the idle speed.

 

[jsalz]

Re: Is my mechanic right? HE SURE WAS!!!

Re: Is my mechanic right? HE SURE WAS!!!

Well, I talked to the mechanic again when I picked up the boat. He told me he referred to the packing as retainers because that is the way they appear in his parts catalog. So he replaced the packing and reset the LS needles. Took her for a 1 hour spin this morning and we were very happy. We got 30MPH GPS out of her. That doesn't sound like a lot but this is a big heavy boat with an undersized motor so we were pretty happy. Anyway, I also asked the mechanic if the previous owner tried to compensate for the Fuel Pump and he said no. He told me flat out that you can't compensate for the fuel pump with the LS idle valves. He said that todays gas (ethanol) is really screwing up old motors ie.gaskets, packing etc. etc. I asked him if he thought the additive available to treat E10 fuel was worth it and he told me not to bother. He did however tell me that the Johnson Outboard oil would make a difference over Non-Johnson. I said, aren't they just putting there name on someone elses oil and he said, they don't make the oil but the people who do make it to Johnson's spec. So I bought a couple of bottles. He hasn't lead me wrong yet! Thanks to everyone who commented. I'm off to catch a nice Walleye dinner.

By the way, the mechanic also said that the needle valves more than likely backed themselves off because the packing gone.

 

[dimock44]

Re: Is my mechanic right? HE SURE WAS!!!

Re: Is my mechanic right? HE SURE WAS!!!

Glad you got it straight. Sounds like you also got a good mechanic

 

[TommyA]

Re: Is my mechanic right?

Wow that is great. Did he explain why the engine was dieing out going to WOT or did the problem correct itself after you rebuilt the fuel pump? I went back and realized that you had not tested the boat after the mechanic adjusted the idle scews. So we need details as to what actually solved the problem!