1984 Johnson 115 not hitting top speed and once warm drops way back

brucehick · Sep 16, 2013

MY J115tlcrd starts and idles great I leave the Dock and boat takes right off but then once warm it drops RPMs big time. Spark and compression are good carbs were just re-built I have run it on external tank as well even replaced prop. Boat mechanic says it could be timming base or power pack. I am done writing checks on this one and have decided to take things into my own hands. Should I just go ahead and replace both power packs? Most of my frustration on this one is that it only happens when its warmed up and in the water running. So when I orgianally brought it to the mechanics they thought I was crazy because of how well everything ran at the shop. Is it tough to replace powerpacks? Thanks in advance for the help

Bob_VT · Sep 16, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

Powerpacks are "plug and play" go here and download the Troubleshooting guide (before you throw parts at the problem) Technical Support | CDI Electronics

brucehick · Sep 16, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

Bob_VT said:
Powerpacks are "plug and play" go here and download the Troubleshooting guide (before you throw parts at the problem) Technical Support | CDI Electronics

Thanks I appreciate the tip. It looks like I am really going to have to do some heavy duty testing to figure this one out.

Daviet · Sep 16, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

You can use an inductive timing light to check the spark to each cylinder while it is bogging down, might help to determine if you are working with a fuel or spark problem.
If you find you loose spark on one side, swap power packs and see if the problem moves with the power pack, if so you have a bad power pack.

brucehick · Sep 16, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

Daviet said:
You can use an inductive timing light to check the spark to each cylinder while it is bogging down, might help to determine if you are working with a fuel or spark problem.
If you find you loose spark on one side, swap power packs and see if the problem moves with the power pack, if so you have a bad power pack.

I am going to switch around the power Packs and see if I see any change in performance. My skill set is pretty low when it comes to the electronic side of this engine. I might have spent my last dollars on saving this one. Frustration level is pretty high! Boat is a 19FT 1984 Grady-White so its probably worth re-powering Improved gas milage and reliability are really starting to sound good. Wish I had not put $$ into it this year.

brucehick · Sep 21, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

brucehick said:
I am going to switch around the power Packs and see if I see any change in performance. My skill set is pretty low when it comes to the electronic side of this engine. I might have spent my last dollars on saving this one. Frustration level is pretty high! Boat is a 19FT 1984 Grady-White so its probably worth re-powering Improved gas milage and reliability are really starting to sound good. Wish I had not put $$ into it this year.

Swapped out power packs no change! Any suggestions besides tests which I'm just not comfortable doing. Should I replace coils? Could that be the cause thanks for the help

James R · Sep 21, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

You may have a fuel pump problem. When the motor fades try squeezing the primer bulb to pump fuel. If the motor picks up then it may be time to dispose of the existing pump and fit a replacement. If you have a VRO then conversion to standard pump for 50:1 is quite straight forward
If this doesn't work then take Daviet's advice to check the sparks.

84Venture · Sep 22, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

I had the exact same issue with '85 120 Johnson. After wasting money on electronics, rebuilding carbs ,installed electric fuel pump for testing and tried remote tank .......almost a year! The problem was the fuel line between the pump and manifold was bad.( lining had come loose, the higher the demand the more restricted it became..the fuel line was less than 3 months old when problem started). Be sure to recheck the simple things, even if it is new!

brucehick · Sep 22, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

84Venture said:
I had the exact same issue with '85 120 Johnson. After wasting money on electronics, rebuilding carbs ,installed electric fuel pump for testing and tried remote tank .......almost a year! The problem was the fuel line between the pump and manifold was bad.( lining had come loose, the higher the demand the more restricted it became..the fuel line was less than 3 months old when problem started). Be sure to recheck the simple things, even if it is new!

Spark is good already did the conversion from the vro It's strange because its only dying when warm. I am beginning to think fuel pump as well. Carbs were rebuilt what would the proper fuel pump be for this engine non Vro. I am thinking that the pump that was installed might not be the right one. I will also check all those fuel lines

keefallan · Sep 22, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

The fuel pump that OMC installed on the 112 specials in the 90's (115 with no vro) was a part # 438556. The rebuild kit for it is 438616(if you don't want to buy a new pump.

brucehick · Sep 22, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

keefallan said:
The fuel pump that OMC installed on the 112 specials in the 90's (115 with no vro) was a part # 438556. The rebuild kit for it is 438616(if you don't want to buy a new pump.

Thanks so much I am looking at the setup that is in place now and it seems off to me does anyone have pictures or detailed instructions on what a non vro pump looks like installed? Mine has this plastic manifold that just does not make sense. I am thinking this conversion was done wrong.
Thanks again for the help

James R · Sep 23, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

Every time I take the time to give a long but complete explanation my log in drops out. Big Boss please note.
Short instruction,the 438556 will not fit on your motor. you need a 438559 with three hose connections, an aluminum plate to mount it to the back of the air box in place of the vro ,new hose and the special hose ties from the dealer.

brucehick · Sep 23, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

James R said:
Every time I take the time to give a long but complete explanation my log in drops out. Big Boss please note.
Short instruction,the 438556 will not fit on your motor. you need a 438559 with three hose connections, an aluminum plate to mount it to the back of the air box in place of the vro ,new hose and the special hose ties from the dealer.

Right now I have a two hose pump that bolts in with the pulse coming from the center hole and it fits fine. Are you saying that I should be using a three hose model pump with the pulse coming from original VRO pulse hose which is now blocked off? Will that give me more fuel flow?

James R · Sep 23, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

No. In the first explanation I tried to send I covered that.
If you have the facility to fit the two hose pump then you can use it. Some motors dont have that, only the output nipple at the base of the crank case. The drawings dont show the capability on your motor. Now back to this plastic manifold. I dont see a plastic manifold on the drawings. do you have a pic?

brucehick · Sep 23, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

James R said:
No. In the first explanation I tried to send I covered that.
If you have the facility to fit the two hose pump then you can use it. Some motors dont have that, only the output nipple at the base of the crank case. The drawings dont show the capability on your motor. Now back to this plastic manifold. I dont see a plastic manifold on the drawings. do you have a pic?

I do have a picture just uploaded it let me know if you can see it. It shows the whole install. Would this pump then be the right one for this engine # 438556 I did not recall seeing a middle hole on the current pump to pick up the pulse so I am questioning the existing pump. Thanks again for all the help!

James R · Sep 23, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

That's the plastic distribution tube that came with the VRO set up and is correct. If you remove the two screws that secure the pump you should see the hole that provides the impulse. I will check to see if the fuel pump is suitable and get back to you.

James R · Sep 23, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

The pump is specified for 1997 115HP motors and is suitable providing there is the porting for it on the block. Have you tried using a jug of fuel mix to feed the motor instead of the tank. Take the fitting off the hose at the tank end and put the hose end in a jug of fuel mix and drive. If you get an improvement then you have an issue with the tank feed.

keefallan · Sep 23, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

Can someone please explain to me and to brucehick how the principal of the 2 nipple pump works? I have it on my 112 spl and I can't grasp how it functions. I have put the 3 nipple fuel pumps on all my v6 crossflows . Those are self explanatory to me.

I was reading in another post that electronics usually after they get warm but work fine. You may have a powerpack issue. What about the grounds to all the coils? Have you looked at all the connections? I have seen firsthand what happens when a motor gets warm and grounds are not clean. Something stops working.

brucehick · Sep 23, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

keefallan said:
Can someone please explain to me and to brucehick how the principal of the 2 nipple pump works? I have it on my 112 spl and I can't grasp how it functions. I have put the 3 nipple fuel pumps on all my v6 crossflows . Those are self explanatory to me.

I was reading in another post that electronics usually after they get warm but work fine. You may have a powerpack issue. What about the grounds to all the coils? Have you looked at all the connections? I have seen firsthand what happens when a motor gets warm and grounds are not clean. Something stops working.

I have not tried running from a jug but have tried an external tank. I am going to go through everything again this weekend. I think I ruled out power packs by swapping them. Not sure about coils but I will look them over. Thanks again and keep the recommendations coming!

Daviet · Sep 23, 2013

Re: 1984 Johnson 115 not hitting top speed and once warm drops way back

On a two hose pump, the pump is mounted directly over a pulse port and a gasket seals the pump to the block. The pulse goes directly to the back of the pump.
On a three hose pump, the pulse is supplied through a hose to the pump and it can be mounted anywhere by use a bracket.

1984 Johnson 115 not hitting top speed and once warm drops way back

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