1984 Evinrude Outboard starving for fuel

Hi Guys,

I have what a believe is a 1984 Evinrude 70 HP with throttle issues. I purchased a boat recently with this motor and it has not run properly since my purchase.

I have the motor in a barrel and it idles fine and it will run like a charm on the lake at WOT. However, it will stall during transition from idle to WOT. If I press the enrichner once or twice as it begins to studder it will get past that part on the acceleration process.

I have cleaned the carbs and done the link and sync and read posts on various forum on this subject till my eye were tired. I have had the motor to a dealer and one other guy that is supposed to be good with outboards. They say the motor is noisy and is not worth putting any more money in.

It has 120 PSI on all 3 cylinders within 1 PSI.

I am just about ready to deep six the thing. I noticed that one of your guys mentioned something about drill out the jets about .002. I have attached a few pictures.

Which jet shown in the pictures needs to be enlarged to get better transition from idle to WOT?

I am also told that the 75 HP Evinrude motors of that era had and adjustable low speed needle and that helped with transition problems. If so, is there a particular year and model I should look for.

Any help would be appreciated.

Thanks,

John

Hi,

First thanks for taking the time to help me and providing the referenced links.

The engine has no Serial No. Plate. I also looked at the welch plug on the top of the engine and couldn't find any number on it either. I bought the boat and motor used and it was not running properly when I bought it. The former owner knew little or nothing about the motors history or issues. I thought the engine was a 1984 due to the type of plug that was on the wires that led to the coils and kill switch. I found this information on the CDi website. Of course, as usual I was wrong. I believe you are correct that the carbs that are shown in the picture which are on my motor are indeed from a 1982 70 HP engine.

First, I tried cleaning the carbs myself and got it to run and with the help of pushing the enrichiner button on the key switch it would sometimes be able to reach WOT and other times it would stall.

Then I took it to a local marine repair store in my area and they attempted to fix it for me. They cleaned the carbs did the link and sync and I believe he said they even experimented with different jets in the carbs. When I got it back it was idling must faster and it would still stall out on acceleration. They said it wasn't worth putting any more money into it to try and fix it. Basically, I paid them to experiment and they had no idea what was wrong. I also believe he said something about a vacuum test that only produced about 3PSI and he seemed to think it should have about 4 to 5 PSI for proper operation. Also, thought MAYBE the pistons had some slop and that may be creating some vacuum issues inside the engine and reducing the fuel draw for proper operation of the engine. Are there any tests that I could perform that would rule out any type of vacuum issues?

I took it to another guy to look at it and he told me it was noisy and not worth fixing. It is hard for me to believe that a engine that will idle O.K. and run at WOT is ready for the junk pile. Of course, I could be wrong?????

I basically don't care if it is a little noisy. I just want the engine to accelerate properly to reach WOT. Is this possible?

I took the carbs back apart for the thrid time and soaked them in NAPA Carb cleaner and re-assembled them. I also put all new fuel lines coming from the fuel pump to the carbs and also new fuel lines that come from the enrichiner pump to each carb.

I will re-check the High Speed fuel jets on the bottom carb bowl.

The fuel pump has not been rebuilt. When I have tried the acceleration tests I had some make sure the primer bulb is properly pressurized.

This seems to be a common problem with this series of motors, judging by the posts on this and other forums. People seem to do a lot of different things to try and fix this issue. The problem I see is that it never seems to be the same solution to fix the problem.

I checked all of the Jets on the side of the carb (Intermediate Jets) per your information and they all have a .067 jet size. Saying that the hight speed jets are clean would enlarging the .067 intermediate jet size (i.e. .070 next number drill size) allow more fuel to enter the engine and provide a richer mixture at the intermediate level of acceleration?

Could it be a vacuum issue or a fuel delivery issue?

Any further ideas or suggestions would be greatly appreciated.

John

Hi,

Thanks for the additional informaton.

I wonder if anyone here can tell me what the actual orfice hole sizes are on the jets you referenced. I checked the intermediate orfice hole size and it is .067. Just wonder if the orfices the marina installed were the correct size or maybe an oversized or undersized orfice. I have the instruments to measure them.

Another question?

I wounder if I could find some 1984 70 HP carbs with the adjustable intermediate needle valves would it be easily to adjust the mid range on a motor that has the age on it that mine has.

John

Post a picture of the cowling.--If original that may instantly identify the year.

Hi,

Here is a picture of the cowling. Of course it has been repainted.

Does this help?

John

No it does not.----------Any pictures of powerhead under that cowling ?

Hi,

Here a few pictures of the powerhead.

John