83 Evinrude 50HP No Top End

[phipps]

I water tested our NTU motor tonight and I just want to double check what I'm thinking.

I ran some seafoam in a gallon of gas through it yesterday and got it running better, but I was never able to run it at full throttle on the seafoam mix. (stupid me didn't think to use it on the lake today)

When I got it on the lake it didn't want to idle very well and I could never get it over about 2500RPM. The throttle did basically nothing between half and WOT. I'm guessing the intermediate and high speed jets are probably clogged and I'm gonna have to tear down the carbs and clean them.

Am I thinking right? Are the carbs my most likely suspect?

I didn't really expect to go out and everything work great, but one can hope! LOL


Thanks,

Gary

 

[Daviet]

Re: 83 Evinrude 50HP No Top End

Before you pull the carbs, check spark and compression to make sure both cylinders are OK. Then move on to the carbs.

 

[kjdunne]

Re: 83 Evinrude 50HP No Top End

If it's been unused for a long time, carbs are a logical place to start. If you can, before you tear them apart, run it on the lake again. Try using the primer at WOT and also pumping the fuel line bulb and see if there is any difference. Improvement when using the primer points to clogged carb jets usually, the fuel line bulb points you toward fuel pump or fuel line problems.

 

[phipps]

Re: 83 Evinrude 50HP No Top End

Improvement when using the primer points to clogged carb jets usually

Actually I did try hitting the primer when I was at WOT and it would rev higher. That's one of the reasons I suspect the carbs.

Should I have the motor on muffs when I'm cranking it to check the compression?

 

[Daviet]

Re: 83 Evinrude 50HP No Top End

You can check compression without the engine hooked up to the hose.

 

[phipps]

Re: 83 Evinrude 50HP No Top End

Thanks guys. I'll check the compression tomorrow and I ordered a couple carb kits tonight.

 

[phipps]

Re: 83 Evinrude 50HP No Top End

Ok, I checked the compression tonight and both cylinders are 120. I did notice that the spark plug for the bottom cylinder was a lot cleaner than the top plug so I've either got a spark issue or fuel issue on the bottom cylinder.

I have a spark tester so the next step will be testing for spark. What is the best way to do that? I know I'll need to pull both plug wires to prevent the engine from starting. What do I do with the wire I'm not testing? Should I ground it to the block or just let it hang? Obviously I don't want to fry a coil or ignition module.

 

[Daviet]

Re: 83 Evinrude 50HP No Top End

Set you tester to a 7/16" air gap and install it to the plug wire.
If you are using the key to turn the engine over, ground the other plug wire to the block.
Spin the engine over and check the spark.
I remove the all the plugs when I check for spark, just lets the engine spin over faster.

 

[phipps]

Re: 83 Evinrude 50HP No Top End

Thanks! That'll be my next step.

I've also ordered a couple carb kits. I figured it can't hurt since the motor has been sitting. Planning on replacing the fuel lines while I'm at it as well.

 

[phipps]

Re: 83 Evinrude 50HP No Top End

ground the other plug wire to the block.

Will a small jumper wire work or do I need something larger?

 

[phipps]

Re: 83 Evinrude 50HP No Top End

Pretty sure I found my problem. Pulled the carbs to clean them. The top was pretty clean but when I pulled the bowl on the bottom carb it had a lot of gunk in the bottom. The high speed jet was completely clogged.

Got them all cleaned up. Hoping to get them back on in the next couple of days and get out and test it on the lake again!

 

[new2boat85]

Re: 83 Evinrude 50HP No Top End

let me know how that works. i have the same motor with, sounds like, the same problem.

 

[phipps]

Re: 83 Evinrude 50HP No Top End

I ended up rebuilding both carbs, replaced all the fuel line and checked the spark. Spark was bright blue across about 1/2" on both cylinders.

We took it out tonight to water test it and what a difference!!! It idled a lot better and wouldn't die when I put it into gear. It ran great at WOT, but I'm only getting 3500-3800RPM. I know that is a prop issue.

What should it be idling at? I'm at about 800rpm in gear. Just a tad over 1000rpm out of gear.