not plaining

[rosser1]

well i put the same post in wrong forums. So here is whats going on. I have a buddy with a 70 hp johnson 70ish model no Serail # found yet. And It will not plain. runs good, short shaft no tilt trim. It will some times plain but not always or right away. it takes throttle up and down then back up a time or two before it wants to plain. He has had boat for many years and kinda always been like this. I am tring to see if this is a common promblem with johnson or what can be done to fix or correct problem. Thanks for your help.

 

[Lion hunter]

Re: not plaining

Has nothing to do with brand of motor or boat. Either the motor is to small for the boat, he has to much weight in the boat (water, gear), or the motor is not running properly. As was told in the other posts we need more info. What size boat, what type boat, what is the max rated HP of the boat, how much does all the gear and passengers weigh ect.

 

[kenmyfam]

Re: not plaining

Needs a lot more info to even start attempting to diagnose this one. Boat, motor info, prop, usual load in the boat and any maintenance history of work done to the motor. Photos showing the transom and motor at the water line would be a huge help as well.

 

[rosser1]

Re: not plaining

ok, boat is a challenger, 16ft. motor is a 70 hp 70 ish model. with orginal prop. has had carb work done a few yrs ago. when buddy went out it was hima nd a friend, so figure 450-500lbs of people and gear. not much gear. no water in boat. The only thing i can think of is that if carbs are set wrong. What is the original setting as far as fuel/air, how many turns out after screw bottoms out. it will throttle up but not plain. thanks guys.

 

[kenmyfam]

Re: not plaining

Well if the motor is in good shape and the flotation foam is not waterlogged the boat should plane out pretty easily.
Reality says you should do a basic health check on the motor to begin with.
Compression
Spark
Fuel delivery
Spark plug condition.

Post results

Go from there.

 

[rosser1]

Re: not plaining

well if it cranks right up then spark and compression should be pretty good, fuel delivery may be the problem. where can i find the carb setting?

 

[tootallofwa]

Re: not plaining

well if it cranks right up then spark and compression should be pretty good, fuel delivery may be the problem. where can i find the carb setting?

look in the "top secret files" post in this section.

I think you're running on one cylinder.

 

[Fishstick]

Re: not plaining

I just had what I believe is the same issue with my 1975 Evinrude 75hp. Would not plane, I would back it off a couple of times and then something would kick over and off she went. I diagnosed no spark on one cylinder and I can tell you that even running on two with the third missing, she fired right up and ran smooth at low speeds, just no power under load. As it was intermittent not constant, I had the power pack/switch box tested. I replaced it this morning and she's running like a top now.

 

[rosser1]

Re: not plaining

thanks for the top secret files that will really help. Just about answered all my future questions!! Thanks guys!!

 

[Fishstick]

Re: not plaining

Test that spark before you go ripping into the carbs, may save yourself alot of time and frustration.

 

[jdicke6]

Re: not plaining

I am currently having the same problem with my boat/motor. I have a 238ccf wellcraft powered by a 1995 johnson outboard. I just rebuilt the motor with help of friends who are very handy. Went to take the boat out this weekend and could not get boat up on plain or get tac over 3000 while under load. We discovered boat was not running on cylinders 2 or 4. We tested all cylinders, replaced coils, plugs and wires. We determined there is a problem in the power pack. I have a new one on the way and hoping that is the issue.

I had a 1976 75hp which also had a bad power pack. Installed a new one and it ran like a champ again.

Get a new power pack after you have established spark plug, coils, and wires are all good.

One other option to consider is that you could have the wrong prop on. A very aggressive prop could bog down your motor under serious load and not allow it to get up on plain as quickly or at all. (not likely but always a possibility)

 

[rosser1]

Re: not plaining

we are in process of checking everything. but like i mentioned, its a buddys boat and with his family and mine, we have to find the time to get together. We thank you for all the output and ideas and will let you know what the outcome is.