Tune up for 1974 85hp Johnson?

[es_bob]

Hey guys,

Recently I got my tach installed so now I can see what my motor is actually doing. My dad said he thought the optimum WOT rpm was between 5000 rpm and 5500 rpm. I have a 19" prop on the boat and when I had it out yesterday (with me, a buddy, two gas tanks and our fishing stuff) it would do 43mph at 4800 rpm. A few weeks ago it would go 46mph (and I don't know what RPM as I didn't have a tach at that point).

I'm wondering what I can do to "freshen" up the motor. Is there something with cleaning the carbs and if so how do I go about doing that? Maybe someone could point me to more information on my motor, I'd greatly appreciate it. My dad said that back in the day when they got the boat it would go 49mph and the rpms were like 5400.

The only things I really know is that the plugs were changed about 3 years ago, and the carbs were never touched since brand new. Last tank of gas I ran seafoam in it and it helped smooth out the lower end of things. Oh and, when I go WOT pulling a skier (like the initial "hit it"), it almost always hiccups, then goes. So what could I do to get back there?

Thanks again guys!

 

[HighTrim]

Re: Tune up for 1974 85hp Johnson?

Id say you definately need a carb rebuild. The seafoam will help, but on a clean carb, run it in your fuel after you manually clean and rebuild your carbs. A manual will be your best friend for this, much better than having ppl try and talk you through it over this forum, although if you do a search you will find thousands of posts on this subject. If you cant get a manual, go to you local library and photocopy the pertinent info. GL

 

[es_bob]

Re: Tune up for 1974 85hp Johnson?

What kind of manual am I looking for? Kind of like a Chilton / Haynes manual for a boat instead of a car? Is it pretty much the same process on any V4 or do a lot of things vary from motor to motor?

Thanks

 

[HighTrim]

Re: Tune up for 1974 85hp Johnson?

Try to get the orininal owner manual. Search ebay for this, it will run you about 30 bucks, but money WELL spent when you have things apart.

 

[jbfisher]

Re: Tune up for 1974 85hp Johnson?

I have this same motor and have the exact same symptoms. Also plan to do a carb rebuild.