Johnson 9.5 Power Problems.

[mattkenton]

Hello!

I have come to this forum over the years and i have yet to have a problem you all could not solve. So here it is...

I have an older Johnson 9.5. It is in really good "running" condition. The only problem is that when it is WOT it seems to being lacking that Umph! The engine has probably not been maintained very well before i got it. And i have done nothing to it since acquiring the motor. It is pushing an 11' American Skiff. Maybe it is under powered but i cannot seem to get the boat onto plane with this engine. I have watched many Youtube videos with this engine on larger boats and it did fine.

Any suggestions? Thanks!

 

[ezeke]

Re: Johnson 9.5 Power Problems.

You may be running on one cylinder. Best to borrow an inductive timing light so that you can monitor each plug through the firing range. Most of those lights need a 12 volt battery to work, but it does not require much power.

Also check compression - instructions are in the "Top Secret File" near the top of the thread list for this forum.

 

[Rick.]

Re: Johnson 9.5 Power Problems.

I was having poor performance issues with mine and it turned out to be nothing more than poorly gapped (by yours truly) points. Re-adjusted and cleaned them and it ran like new again. Best of luck. Rick.

 

[jbjennings]

Re: Johnson 9.5 Power Problems.

I believe the problem is with the boat. An 11 foot boat is difficult to get on plane. ALL of the weight will be toward the rear and it's difficult for a little 9.5 to push all that weight "over the hump". I've found my 14foot aluminum boat to be far easier to plane than my 12 foot aluminum boat.
How much do you weigh? If you weigh over 200, I'd almost bet that the boat length is your problem. Otherwise, I'd think one cylinder is not firing as was mentioned.
JMO,
JBJ

 

[5150abf]

Re: Johnson 9.5 Power Problems.

Being an older engine and you not having dione anything to it yet I woud start by cleaniong the carbs, that is by far the most common cause of badly running engines.

The high speed jet is located in the bottom of the float bowl and is the first thing to get dirt in it causing the problem you mention so start there.

DO them one at a time and keep the jets with the covers so you don't mix them up, you have to physically clean the jets with a stranded copper wire, just taking the carb apart won't do anyhting.

 

[ENSIGN]

Re: Johnson 9.5 Power Problems.

Since you said it runs good put the old lady up torwads the bow and give it a try!

 

[mattkenton]

Re: Johnson 9.5 Power Problems.

I tried the weight forward and it just wont go.

I will try all of the following, doing the least task involved first, then moving forward one by one. The one cylinder idea and dirty carbs sound like the most likely problems. I think i may have ran some dirty gas through it too.

Before i do anything, should i run some Sea Foam through it? Just to see if it was some bad gas?

Thanks for all the help so far!

 

[bradmond]

Re: Johnson 9.5 Power Problems.

What prop do you have on it? It may be to much and it won't rev up.

 

[mattkenton]

Re: Johnson 9.5 Power Problems.

I have the stock prop on it. 8.5 pitch 8.25 diam.

 

[kbait]

Re: Johnson 9.5 Power Problems.

One spark test is easy. Get it running and hit kill button. Then pull one plug wire off and run. Do the same w/the other and you'll know, w/o shocks. I have some insulated pliers I use while motor is running.. But if you pull a plug wire and it runs the same..
Those 9.5's weren't powerhouses, but should plane any 11'er.