1998 115 Johnson Intermittent RPM Loss

[midsized johnson]

Well, true to form, fix one thing, then something else pops up. I went out Friday, got up to speed at around 5000 rpm and a sudden loss of about 2 grand, then bounced back up to full speed. I started thinking about it, got my son to pump the squeeze bulb and she ran fine. I assumed since my son became the fuel pump, that it must be the problem. The service guy at the shop I bought the rebuild kit told me it could have been a fuel restriction too. I went ahead and did the rebuild, checked fuel lines, everything looked fine. I was pretty sure it wasn't the fuel pump as both diaphrams looked fine on visual inspection. I did the rebuild anyway. This is a VRO fuel pump, BTW. I cleaned everything up real well in the stuff above the fuel pump, not sure what it all is, but there's a bowl with a float in it and the primer mechanism is mounted on it as well. All of it seemed clean enough when I took it all apart, but shot carburetor cleaner in it anyway. Long story short, it ran great yesterday until we headed in, then it started the rpm loss again with pumping the squeeze bulb fixing it.
I noticed a bit of fuel around the inline fuel filter that mounts next to the fuel pump and tightened it up, ran new fuel line and removed the quick connect fitting at the tank and put in a hose barb with a hose clamp. I dumped the fuel and there was no appreciable amount of gunk in the tank and nothing clogging the fuel pickup when I pulled it out. I also replaced the squeeze bulb as I figure it might be a remote possibility that the check valve was malfunctioning.
I have a manual for my year model's engine, but it's for an SPL, which appears to be quite different than my ELECM, as I found nothing about the stuff above the fuel pump.
Anyway, if anybody has a take on what's going on, and what I could have missed, I'd appreciate the input.

 

[oldcatamount]

Re: 1998 115 Johnson Intermittent RPM Loss

Is the fuel tank venting right? If it's not, that could be the likely culprit.

 

[midsized johnson]

Re: 1998 115 Johnson Intermittent RPM Loss

Is the fuel tank venting right? If it's not, that could be the likely culprit.

Good call, forgot to mention that the vent checked out fine.

 

[trendsetter240]

Re: 1998 115 Johnson Intermittent RPM Loss

I cleaned everything up real well in the stuff above the fuel pump, not sure what it all is, but there's a bowl with a float in it and the primer mechanism is mounted on it as well. All of it seemed clean enough when I took it all apart, but shot carburetor cleaner in it anyway.

This is the vapor separator pump. As the name implies, it separates liquid fuel from fuel vapor. Only the liquid fuel is passed to the fuel pump.

Long story short, it ran great yesterday until we headed in, then it started the rpm loss again with pumping the squeeze bulb fixing it.

Well, if it ran great for awhile again but then started with the same old issue I doubt it's the fuel pump itself. More likely there is an air leak in one of the fuel lines somewhere in the system. With the engine cover off, pump the fuel primer bulb up until it is rock hard. Are there any fuel lines or junctions leaking even a little bit of fuel?

 

[midsized johnson]

Re: 1998 115 Johnson Intermittent RPM Loss

Thanks Trendsetter, pumped it up, looks like everything's holding. As I mentioned, I don't have the correct manual for this motor yet, but one is on the way. I looked at a parts diagram and saw where the pulse limiter is. I understand that if it is carbed up, it can affect the fuel pump which makes sense. I'm taking it out tomorrow to rule it out.
Another question, since this motor has a vapor separator, can you still replace the VRO pump with a regular fuel pump? Looks like a lot of stuff to bypass if you went that route.

 

[trendsetter240]

Re: 1998 115 Johnson Intermittent RPM Loss

Thanks Trendsetter, pumped it up, looks like everything's holding. As I mentioned, I don't have the correct manual for this motor yet, but one is on the way. I looked at a parts diagram and saw where the pulse limiter is. I understand that if it is carbed up, it can affect the fuel pump which makes sense. I'm taking it out tomorrow to rule it out.
Another question, since this motor has a vapor separator, can you still replace the VRO pump with a regular fuel pump? Looks like a lot of stuff to bypass if you went that route.

Yes, you can put a standard fuel pump on there. The vapor separator has it's own crankcase pulse connection so it will operate independently. I recently looked into replacing the vro on my 96 115 with a regular pump and it was possible.

 

[midsized johnson]

Re: 1998 115 Johnson Intermittent RPM Loss

So far, everything checks out good. The pulse limiter looked brand new, sprayed it with carb cleaner and it came out clear. I'm going to replace the rubber gasket at the top of the vapor separator housing as it is flattened in a couple of places just to rule that out. What else could I be missing?

 

[trendsetter240]

Re: 1998 115 Johnson Intermittent RPM Loss

I noticed a bit of fuel around the inline fuel filter that mounts next to the fuel pump and tightened it up, ran new fuel line and removed the quick connect fitting at the tank and put in a hose barb with a hose clamp. I dumped the fuel and there was no appreciable amount of gunk in the tank and nothing clogging the fuel pickup when I pulled it out. I also replaced the squeeze bulb as I figure it might be a remote possibility that the check valve was malfunctioning.

Have you taken the boat out again since you made these changes?

 

[Faztbullet]

Re: 1998 115 Johnson Intermittent RPM Loss

Yes, you can put a standard fuel pump on there. The vapor separator has it's own crankcase pulse connection so it will operate independently. I recently looked into replacing the vro on my 96 115 with a regular pump and it was possible.

I would like to see how this is done as the vapor separator supplies fuel to VRO, not to it.

 

[trendsetter240]

Re: 1998 115 Johnson Intermittent RPM Loss

I would like to see how this is done as the vapor separator supplies fuel to VRO, not to it.
View attachment 182401View attachment 182402View attachment 182403

So are you saying it will not work with a fuel only pump? The fuel only pump has an inlet (from tank), and outlet (to carbs) and a crank case pulse connection. So why can't it be connected in the same way the VRO is connected to the vapor separator?

 

[midsized johnson]

Re: 1998 115 Johnson Intermittent RPM Loss

Have you taken the boat out again since you made these changes?

Not yet, likely not until the weekend.
Turns out, previous owner had the rpm loss issue, but neglected to tell me about it. Funny thing though, it ran like a champ everytime I had it out, maybe 9 times without issues. Seems like it started at upper end rpms, because Sunday when I ran it at 4-4500 rpm's it never had rpm loss. On the way in, I nailed it and was at about 5500 when it started doing it again.
Is this a possible scenario? I was low on gas, there were a few solids in the gas that I put into another tank through a cloth filter, so I wonder if low on gas, picking up the crud, might be causing it to intermittently starve for fuel? Maybe I'm just overthinking the whole thing, and just fixed the problem by cleaning out the fuel tank? Again, the screen on the fuel pickup was clean on visual inspection as were all passages and fittings.

 

[bob johnson]

Re: 1998 115 Johnson Intermittent RPM Loss

I thought the hose that went from the fuel bracket assy to the pulse limiter came from the fuel pump portion of that bracket assy. because mine was split, and i had to replace it. and from memory it went right onto that pump.


i wonder if you have a water seperator/fuel filter cannister set up?

if not do you have any other fuel filter other than the one on the front of the fuel bracket assy???

you should...I have the same motor and I have the fuel seperator and an inline fuel filter...

intermitant problems are certainly the hardest to trouble shoot...

one reason i have a spare parts motor for all my outboards... i can replace parts to check for problems and if it wasnt bad, i just leave it and install that removed part back onto my parts motor.. and move onto another guess.

not the best....but sometimes the tests the book wants you to perform are complicated and need tools or devices you might not have on hand.

good luck


bob

 

[midsized johnson]

Re: 1998 115 Johnson Intermittent RPM Loss

i wonder if you have a water seperator/fuel filter cannister set up?

if not do you have any other fuel filter other than the one on the front of the fuel bracket assy???

you should...I have the same motor and I have the fuel seperator and an inline fuel filter...

intermitant problems are certainly the hardest to trouble shoot...

one reason i have a spare parts motor for all my outboards... i can replace parts to check for problems and if it wasnt bad, i just leave it and install that removed part back onto my parts motor.. and move onto another guess.

not the best....but sometimes the tests the book wants you to perform are complicated and need tools or devices you might not have on hand.

good luck


bob

Thanks Bob. I have a water/fuel separator, an inline filter, then the filter at the pump. Two are brand new and the filter at the pump I cleaned when I did the fuel pump kit. I'm going to try using a spare gas tank and see if I can isolate that end. I can't figure out how the regular fuel pump would be installed in place of the VRO, but I'm certain it can be done, which may be the next thing I try if my latest efforts aren't the fix.

 

[trendsetter240]

Re: 1998 115 Johnson Intermittent RPM Loss

Thanks Bob. I have a water/fuel separator, an inline filter, then the filter at the pump. Two are brand new and the filter at the pump I cleaned when I did the fuel pump kit. I'm going to try using a spare gas tank and see if I can isolate that end. I can't figure out how the regular fuel pump would be installed in place of the VRO, but I'm certain it can be done, which may be the next thing I try if my latest efforts aren't the fix.

I wonder if the extra two filters are causing too much of a restriction. Can you remove the inline filter and test with just the F/W separator and the filter at the pump? Also, make sure the fuel lines you are using at 3/8 inner diameter minimum.

 

[bob johnson]

Re: 1998 115 Johnson Intermittent RPM Loss

I wonder if the extra two filters are causing too much of a restriction. Can you remove the inline filter and test with just the F/W separator and the filter at the pump? Also, make sure the fuel lines you are using at 3/8 inner diameter minimum.

I have 3/8th ID lines and the 2 filters as described..and my motor runs to 6000 rpm!!!.....i have a 1995 115 ocean runner.... so the same motor basically.


once he figures the furl issue... and gets no obvious solution , he is then onto intermitant electrical woes!!!


best of luck

bob

 

[trendsetter240]

Re: 1998 115 Johnson Intermittent RPM Loss

I have 3/8th ID lines and the 2 filters as described..and my motor runs to 6000 rpm!!!.....i have a 1995 115 ocean runner.... so the same motor basically.


once he figures the furl issue... and gets no obvious solution , he is then onto intermitant electrical woes!!!


best of luck

bob

Yeah, I have the 96 115ELED which is the same motor as his. Mine does not have an inline fuel filter. Just the F/W separator and the filter at the fuel bracket.

Also the EL models (mine and his) shouldn't be run above 5500 RPM (not sure about your ocean runner).

 

[bob johnson]

Re: 1998 115 Johnson Intermittent RPM Loss

Yeah, I have the 96 115ELED which is the same motor as his. Mine does not have an inline fuel filter. Just the F/W separator and the filter at the fuel bracket.

Also the EL models (mine and his) shouldn't be run above 5500 RPM (not sure about your ocean runner).

I have heard from a number of more informed mechanics, and experienced boaters that the 60 degree loopers in V4 love rpms...


5800-6000 rpms is what the recomendation was..... dont know why, but the Intruder and Fast Strike 115's ( gl models) max rpms were 6000!!

i have propped my motor to run WOT at 6000 rpms and it has been set up tat way for 4 years now..... i run mainly in the winter, but I run it in the summer on ocassion, ( i do use extra oil in the winter )

I have the same compression i did 4 years ago.

bob

 

[trendsetter240]

Re: 1998 115 Johnson Intermittent RPM Loss

I have heard from a number of more informed mechanics, and experienced boaters that the 60 degree loopers in V4 love rpms...


5800-6000 rpms is what the recomendation was..... dont know why, but the Intruder and Fast Strike 115's ( gl models) max rpms were 6000!!

i have propped my motor to run WOT at 6000 rpms and it has been set up tat way for 4 years now..... i run mainly in the winter, but I run it in the summer on ocassion, ( i do use extra oil in the winter )

I have the same compression i did 4 years ago.

bob

That's good to hear your motor is doing well at the higher RPMs. Yeah, my factory manual lists the GL models at 5000-6000 and the EL as 4500-5500. So I have mine propped to hit 5500 WOT and she sounds happy!

 

[midsized johnson]

Re: 1998 115 Johnson Intermittent RPM Loss

I have 3/8th ID lines and the 2 filters as described..and my motor runs to 6000 rpm!!!.....i have a 1995 115 ocean runner.... so the same motor basically.


once he figures the furl issue... and gets no obvious solution , he is then onto intermitant electrical woes!!!


best of luck

bob

That's my fear! I'm still figuring it's fuel delivery as the squeeze bulb fixes the situation and it only happens at or near upper end. There is a wiring harness at the fuel pump, I assumed the pump ran only off of the vacuum from the engine. Is it possible there's something electrical going on there? My mechanic buddy mentioned power packs, but I can't see how squeezing the fuel bulb would make it run better in that situation.

 

[bob johnson]

Re: 1998 115 Johnson Intermittent RPM Loss

That's my fear! I'm still figuring it's fuel delivery as the squeeze bulb fixes the situation and it only happens at or near upper end. There is a wiring harness at the fuel pump, I assumed the pump ran only off of the vacuum from the engine. Is it possible there's something electrical going on there? My mechanic buddy mentioned power packs, but I can't see how squeezing the fuel bulb would make it run better in that situation.

I think the wiring is for the alarms the vacum switch and electric primer solenoid..... but I dont think the fuel pump is electrically driven in any form....but the oil portion of the pump takes signals from the motor based on rpm to delever a VARIABLE amount of oil...thus the VRO( variable ratio oil)...

good luck

bob