1978 johnson, 200hp, playing up

[Mandy Torrens]

I have an old girl Johnson that normally runs really well. I had a hand in totally stipping it down and rebuilding it last year, so know enough to be dangerous when it comes to repairs.<br /><br />It has just started to smoke when it idles, not steam, white, grey smoke and lots of it. I haven't changed the fuel mix, which is new. 50:1. haven't changed the type of oil I normally use.<br /><br />I have been fiddling with the throttle lever on the engine, to try and get her to start a bit better..sometimes these old girls take a bit of turning over. But I may have done something which has resulted in the smoke.<br /><br />It also has power surges at around 30mph, up to about 38mph, through no movement in the throttle control. very frustrating for water skiing!<br /><br />Both fuel pumps have been rekitted when the engine was rebuilt. <br /><br />There are two cables going from the control box to the engine, one for the throttle and I'm not sure what the other one underneath is. They both have adjustment wheels on them. Does one adjust the idle speed?<br /><br />Although I should probably leave well alone and let the experts fix things for me, I find it very satisfying and a lot faster to fix things myself...if I had a bit more knowledge, I wouldn't be so dangerous with it.<br /><br />Any ideas would be greatly appreciated.<br /><br />Thanks

 

[marinegrh]

Re: 1978 johnson, 200hp, playing up

that other canle is your shift cable, dont mess with it, do your carbs have idle mix screws on them or are they fixed jets, if fixed the couls have some bugs in them, seriously, little g nats as we southern folk call them like to crawl in there and take dirt naps, if they are adjustable, give each one a turn clockwise about an 1/8 of a turn and listen and look for smoother idle, also those carbs were known for the venturis to wear out causing a surge between mid range and top out........let us know how you fair out

 

[fireman57]

Re: 1978 johnson, 200hp, playing up

You might pull your plugs and see if one (or more) is burning lean. If you find one that is then you should be able to tell which carb it is coming from and concentrate onit. White smoke usually indicates you are burning a little water with your fuel. I know you said it is not steam and I hope you are right.

 

[Walker]

Re: 1978 johnson, 200hp, playing up

Sounds to me like a good carb overhaul/cleaning is in order.

 

[jy118lfd]

Re: 1978 johnson, 200hp, playing up

I have a 78 150 and the old crossflows start extremely well when cold. I would clean the carbs and install new kits before proceeding to anything else

 

[walleyehed]

Re: 1978 johnson, 200hp, playing up

I would pull all plugs and see if one of them is super clean....just a hunch. If not, still continue with a carb O/H, check all intake mounting bolts while you have the carbs off.<br />Did you do the fuel pumps when you rebuilt???<br />Check the torque on the cyl. head bolts...they should have been re-torqued a few hours after break-in.<br />I believe I would do a compression check as well.<br />Let us know what you find!

 

[Mandy Torrens]

Re: 1978 johnson, 200hp, playing up

Thanks everyone for your feedback. I will try all of those things. Some of the more indepth ideas may mean I have to seek expert help, but will do what I can first.<br /><br />Thanks again.<br /><br />M