75 johnson

[geoff69]

Morning all.
Well here I am again .This time I have acquired a Wescraft 17 with a 1976 75 hp johnson .
Took it out for a shakedown cruise on Sunday and was very pleased.Only problem was after about 1/2 an hour it slowed right down and we could not get it to pick up again. I have to emphasize it never actually stopped but a fastish tickover was all we could get.I did switch tanks halfway through and thought that some garbage from the bottom of the tank was clogging the fuel filter but when I checked it when I got home it appeared clear.I have not yet checked out the carburettors(3 of) but don't see why it would be that if the filter was clear.
All suggestions would be appreciated.
Geoff.

 

[steveo32]

Re: 75 johnson

Was the gas new? Also it is new to you so don't assume anything, carbs would be your next step take them apart and clean them, and also check your spark plugs to see if they are fouled. It almost seems like you lost a cylinder, because the boat didn't stall out it just lost power suddenly. You should probably check the spark to make sure your getting good spark on all cylinders. Also check the coils for any cracks, if present they should be replaced even if they are still working. Get this doen and post your findings and someone with more knowledge can help you further if these don't solve your problem.

 

[tashasdaddy]

Re: 75 johnson

did it overheat, over heating will cause one to slow down. start with the basics, check compression and spark. to make sure you have a good base to start with. has this motor been sitting for a period of time?

 

[5150abf]

Re: 75 johnson

Replace plugs, I have seen "clean" plugs that wouldn't fire, confirm spark to all cylinders, compression check if you can and then clean the carbs.

The carbs are the easiest mose likely cause and they will just plug up, it doesn't take much.

I have used a dental syringe(just has a plastic tip) to squirt a bit of gas in the cylinders with the motor running, if you get one to hit when you spray gas in it you have found the problem.

Also once you get it running do a good decarb on it.

 

[geoff69]

Re: 75 johnson

Thanks for the help friends.I looked at the plugs this morning and two were very wet and one was dry,the gaps also looked too small but I have not checked them yet.I will fit new during the week just to be sure,am doing the compression check and working on the carbs right now Thanks again.
Geoff69.

 

[geoff69]

Re: 75 johnson

Checked compression,90 to 120 range on all three,regapped plugs,checked sparks ,all ok.Down to lake to test run.Maybe 200 to 500 rpm improvement so really not much change.carb stripdown next.
Geoff69

 

[geoff69]

Re: 75 johnson

I think I've found the cause of my problem.I have stripped and rebuilt the carbs,checked compression ,new plugs and synchronized.Put it all back together and started up (in tank).No change still nothing going on in #3 Then I noticed it was spitting fuel back out through the carb.A quick scan through the manual indicated a reed problem so I took off the carbs again and removed the outer reed plate but I'm darned if i can shift the two lower Phillips screws on the inner plate ,I don't want to round the slots or I'll end up having to drill them out.Any suggestions anyone.I suppose next prob is going to be finding the broken piece of the reed.
Do reed boxes come singly or do you have to get the whole set? What do they cost? Any info on this subject appreciated.
Geoff69

 

[tashasdaddy]

Re: 75 johnson

come as plates. http://shop2.evinrude.com/ext/index.aspx?s1=bf6ad09c53cead335fcfd8a6471c0f7f

 

[geoff69]

Re: 75 johnson

Problem solved again,I didn't realize that you could remove the entire plate and the reed boxes with it,I got the screw undone anyway,and guess what i found when I took out #3 reed box.Yes,you,re quite right,it was a machine screw wedged under the middle reed,and no,it was not one of the reed stop screws,it looked more like the screws that retain the air silencer,10-24 3/4 inch.How that got in there I,ll never know.My best guess is it was left in there on some previous stripdown.Anyway,as soon as I get the new gaskets from Seaway I should be up and running.I'll let you know how it goes.Thanks for all your helpfull advice,of course it's not over yet,I have three other motors to overhaul.
Cheers, Geoff69.