1986 Force 125 losing power on full throttle

binghaml

Cadet
Joined
Mar 28, 2015
Messages
14
Hi all, I've been reading these forums for a few months now. Figured I'd finally make an account as I'm stumped!

The boat is a 1986 Bayliner Capri open bow, with a Force 125 2-cycle engine. I'll start by listing the things I've done so far to try to solve my issues:

When I first bought the boat, I was losing fuel extremely fast, couldn't idle, and eventually started losing power / cutting out at full throttle.

Compression test - good on all cylinders
Carburetors professionally rebuilt and cleaned - fixed nothing (engine was not run until the next 2 things were done)
Every inch of fuel line on the boat replaced - fixed nothing
Installed a water/fuel separator - preventative - fixed nothing
Linkage professionally adjusted - fixed nothing
Replaced fuel pump diaphragm - Solved all problems! Boat idled great, full power, smooth acceleration, nirvana achieved, etc.

Unfortunately, this was for about 3 hours of run time, over 2 outings. Then I started to have an intermittent problem. It would run great for a few minutes then lose power and die. Then it was impossible to start for 5-10 minutes, after which time it would run perfect for a few minutes again. Over a few cycles of this while trying to diagnose, the problem would last longer, and come on quicker. It seemed electrical, I pulled the boat home.

At home I found I had no spark on cylinder 3. Hooked my battery up to a trickle charger for the first time (just got this boat late last year) and let it sit for a week until I had time to work on it again. I switched the wiring so that the CDI modules would be swapped, hoping that my no-spark cylinder would follow. Even better - or worse in my opinion, I had spark on all 4! I switched the wiring back to its original state and still had spark on all 4 cylinders.

Cautiously optimistic I took it to the lake, as any boat owner knows, if you want to re-create your problem - just simply try to use the boat. It fired up great, idled fine. I let it warm up and pulled away from the dock. It picked up well, and was running fine and I was doing short full throttle runs - not even reaching full speed.On my 3rd full throttle run I lost power. The engine didn't die, but it bogged down to idle basically. After idling for a minute, it would have power again. Only for a few seconds before bogging back out. So, this sounds like another fuel problem to me. This is where I'm at now.

my questions:
1) Is it possible for my battery to have a low enough charge to make me lose spark to a cylinder, while still being able to turn the motor over? It's the only thing I can think of as to why the spark came back, since I charged the battery.

2) If it's a fuel problem, do you think it could be the fuel reeds? I just found out about these recently, and it sounds like they operate similarly to the fuel pump diaphragm, so perhaps the same thing that damaged the original diaphragm could have damaged the reeds?

3) Also fuel problem related. I've been told I should clean the fuel tank out. I bought some super powerful magnets to push around in there with a coat hanger or something, but it makes me anxious. Not only could one fall off, but it could break loose sediment/things that wouldn't have been a problem before. Is this a good idea?

4) If the electrical problem is not explained by my theory in question 1, and I can only seem to get it to act up during a full throttle run, how in the world could I test what cylinder isn't getting spark in order to diagnose it?

I appreciate you taking the time to read this. I feel like I'm running out of possible causes to this problem, which must mean it's getting close to finally functioning properly!
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,923
Welcome!
#1 No the motor should make power to run itself. The 86 has the plug in connectors and they were probably corroded.

#2Reeds? If it runs and doesn't have fuel coming back through the carb the reeds are probably good. It will spit fuel out while running and probably run real crappy.

#3 NO!!!! Rubbing metal in a gas tank could cause sparks.BOOOOOM!! Remove the fuel. Remove the fuel tank sending unit.Look inside with a flash light. Some tanks had a screen on the end of the pick up tube. See if you have this.It can get clogged.
Run it on a spare tank and see if there is any difference.

#4 The only way to check for dropping a cylinder is a spark tester and go for ride.

The built in tank has a vent hose. Make sure it's not clogged. Bug like to get in there and build nests.
When the carbs were rebuilt it's possible the floats weren't set right?
 
Last edited:

fisheymikey

Chief Petty Officer
Joined
Jul 30, 2012
Messages
450
ok bud here it goes...
Above all REDO all CDI and trigger connectors. no exceptions. that is most likely the Pro's here are going to recommend because the wires sometimes breaks underneath the shrink.

for me also the trigger harness just underneath the flywheel tug on it. i also had a broken wire (that i could not see) do an intermiten problem

inline fuel filter to determine if you are getting fuel to carbs

if i was a betting man i put my money on the wires being broken
 

binghaml

Cadet
Joined
Mar 28, 2015
Messages
14
Thank you guys for the fast replies!

Here's my plan of attack:
First, I'll check the fuel filter to make sure it's not clogged. Then I'll look in the gas tank to see if I can see the pickup tube and determine if it has a clogged screen. Then I'll check the trigger harness for broken wires. At this point I'll try to take it to the lake with a separate fuel tank. If the problem persists, then I will dive in and replace all the CDI connections (by the way, how annoying is it that they would break under the shrink?! haha).

I will report back with my findings, once we get some non-rainy weather here in Seattle!
 

SkiDad

Lieutenant Commander
Joined
Jul 18, 2010
Messages
1,518
check out outboardignition.com - it has helped me. Wish you were close I would loan you a spare CD module.

This suckers electrical - 1.21 GigaWatts!!! i couldn't resist
 

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,817
Let me chip in my 2 cents. Go to Walmart and buy a G2 fuel filter (clear fuel filter, costs less than $5) and install it between the fuel pump outlet and the carb inlet. Make sure you prime it good and should fill at least 3/4 full. Now try running the motor at the driveway with a garden hose with the upper cowling off. Rev it intermittently but not to exceed 3K RPM. Watch the clear fuel filter and see if it stays at least 3/4 full and not bubbling. If there are bubbles, it indicates there is air leak from the fuel hoses upstream of the fuel filter. If it doesn't stay at least 3/4 full then it means the fuel pump is not delivering proper amount of fuel or a leak or a clog in the hoses or even a clogged tank vent or pick up tube.

If the fuel filter stays full, then you know it is not a fuel delivery related problem but more of a carburetion problem or reed problem or electrical. The electrical can easily be diagnosed with an inline spark tester. The reed or carburetion problems will take some disassembly to find out.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,923
The 86, most came with the plug and play connectors.
The later models had the screw down connectors.
Model# ??? Pics?
Don't forget the tank vent line.
 

gregmsr

Petty Officer 1st Class
Joined
Sep 20, 2006
Messages
391
I had a similar issue once and turned out to be the exhaust leaking into the cowl..
It would run fine at home in a tank with the cowl off...go to the lake it would bogg down when running at speed with the cowl on.
Check the exhaust boot connection to the pee holes...may be torn or in my case just not completely on..
 

binghaml

Cadet
Joined
Mar 28, 2015
Messages
14
The 86, most came with the plug and play connectors.
The later models had the screw down connectors.
Model# ??? Pics?
Don't forget the tank vent line.

I have the screw down connectors. The only plug and play connectors I saw went from the CDI modules to the coils (behind the CDI modules when installed on the engine). I can provide pics and model number the next time I am at the boat (not kept at my house).

Let me chip in my 2 cents. Go to Walmart and buy a G2 fuel filter (clear fuel filter, costs less than $5) and install it between the fuel pump outlet and the carb inlet. Make sure you prime it good and should fill at least 3/4 full. Now try running the motor at the driveway with a garden hose with the upper cowling off. Rev it intermittently but not to exceed 3K RPM. Watch the clear fuel filter and see if it stays at least 3/4 full and not bubbling. If there are bubbles, it indicates there is air leak from the fuel hoses upstream of the fuel filter. If it doesn't stay at least 3/4 full then it means the fuel pump is not delivering proper amount of fuel or a leak or a clog in the hoses or even a clogged tank vent or pick up tube.

If the fuel filter stays full, then you know it is not a fuel delivery related problem but more of a carburetion problem or reed problem or electrical. The electrical can easily be diagnosed with an inline spark tester. The reed or carburetion problems will take some disassembly to find out.

This seems very useful! Saves me a trip or more to the lake! I'm excited to try this out - it seems like it would do a lot in narrowing the problem down, and I can do it relatively quickly.

I had a similar issue once and turned out to be the exhaust leaking into the cowl..
It would run fine at home in a tank with the cowl off...go to the lake it would bogg down when running at speed with the cowl on.
Check the exhaust boot connection to the pee holes...may be torn or in my case just not completely on..

I had that problem when I first bought the boat.. I replaced the exhaust boot, but it would probably be a good idea for me to double check the installation and make sure it's holding up.
 

binghaml

Cadet
Joined
Mar 28, 2015
Messages
14
the other day I was looking on Ebay and saw this

http://www.ebay.com/itm/1987-125-HP...ILS-/111636914658?hash=item19fe1421e2&vxp=mtr

I picked up a similar unit over the winter for even cheaper just for some spare stuff - I was gonna post this a few days ago when it had a 150.00 buy it now but I thought you have the older style snap connectors - you must have the 1986 B motor which is like the 1987-1988

Dang, this looks useful. Not sure if I could use any of the parts off of it though.. Instead of the 12 screws for connections, I have 8.
 

binghaml

Cadet
Joined
Mar 28, 2015
Messages
14
I've been slammed with school and work lately, but here's a quick little update:

Purchased some "earmuffs" so I can get water to the engine while it's in the driveway.

Purchased clear fuel filter. Will be installing it this weekend and seeing what happens to the fuel when the motor is running.

Went to check some stuff on the trailer today since I had a few minutes. I cranked the landing gear all the way up and noticed I must have not got all the water out of my bilge before I parked it last as I could hear it splashing out the drain hole in the back. I walked to the back and realized it was FUEL DUMPING OUT! Lots of it! I ran back and lowered the landing gear again to stop it.

I found the leak, it was on the vent tube, just a few inches from the tank. I've almost got the tube out (it got dark before I could finish) and should be able to finish that up this weekend. Could this possibly make the engine cut out at full throttle? I still plan on installing the clear filter and seeing what happens with the fuel, but if this is a possible cause then I think it may be the reason.

As far as I can tell though, the only way a vent tube would cause fuel delivery problems would be if it was plugged therefore creating a vacuum in the tank.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,923
IF the vent line was broken. It could have let water in the tank.
Check for water in the fuel.
Your right it would create a vacuum and not allow fuel to move.
 

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,817
When you get a chance can you post a pic of the leaking vent tube. It is quite unusual liquid fuel will leak out of the vent tube considering it is located on top of the fuel tank. I understand fuel fumes can escape if it is broken but why liquid fuel?
 

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
I'm thinking that the boat might be tilted so the all of the fuel is at one end of the tank so that the vent tube is submerged in gas so any pressure in the tank is pushing gas out, not air. If your vent tube is placed at either the front or rear portion of the tank, this might be the cause.

I have this problem on my Bayliner. The vent tube on my tank is attached at the very back of the tank. If I store my boat on the trailer and raise the front of my trailer up as far as it will go with a 3/4 to full tank of gas, on a hot day after a few hours, gas will start coming out of the vent tube. I just lower the front of the trailer back down and you can hear the pressure release through the vent. My tank is 20 gallons but only about 8 or 9 inches deep, so I think it aggravates the problem.
 

binghaml

Cadet
Joined
Mar 28, 2015
Messages
14
Another update:

I have replaced the vent hose - sorry I can't get a picture of it. It had a spot where the hose degraded and kind of tore, and that spot was very close to the height of the nipple on the tank. I got about 3-4 gallons of fuel out of the bilge - I started to wonder if it was ever going to stop haha. I think the reason so much fuel came out is that I filled it up after the last time out, and at the time it was relatively cold out (~45 F), lately it has been closer to 70 F and sunny around here so there's probably some expansion. I think another factor is like pnwboat said, the tank is about 20 gallons, but very shallow, so if you only have a small pocket of air in the tank, it would have to purge quite a bit of fuel before it reaches the air, if the boat is sitting at the right angle for that situation.

I also installed a clear fuel filter between the fuel pump and the carburetors. At idle, or slightly elevated rpms (sub 2k or so) the fuel filter stays at the level it was primed to, and there's no bubbles or anything of concern that I noticed. I ran it up to 3k, no higher since it was out of the water, but the filter drained quickly at 3k rpms. So I have a fuel delivery problem. Since all my fuel lines are new, and I just installed the fuel/water separator (should I already need a new one after maybe 10 hours of use?) then it must be a clogged screen in the fuel tank, if it has one. I haven't checked it yet because I'm not set up to store 20 gallons of fuel. I have 2 5 gallon portable tanks, maybe I'll take it out and troll around for a while to burn enough gas to fit the remainder in the portable tanks.

https://youtu.be/z8rT6MrYxQg

I took a video of the clear fuel filter at about 1500 rpms. I didn't feel comfortable recording a video with the motor at higher rpms, I felt like I might need to shut it down real quick just in case - and having my phone in my hand wouldn't have been good. Anyway, the problem is indeed fuel starvation. I think my next step is to find out how to deal with the 15-20 gallons of fuel left in the tank, then try to find the pickup screen.
 

SkiDad

Lieutenant Commander
Joined
Jul 18, 2010
Messages
1,518
When you replace all the fuel lines... Did you replace the squeezy? also have you tried running off of a small tank?
 

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,817
Clear fuel filter is indispensible for troubleshooting fuel related problems especially with top speed related problems. The next step of the troubleshooting is to isolate the source of "blockage", leaks or even faulty fuel pump. The most expeditious way is to use a portable gas tank (PGT) with a separate fuel hose and primer bulb. Disconnect the existing fuel hose from the fuel pump inlet conn and then connect the PGT hose. Test run again (making sure the PGT vent is open) and see if the clear fuel filter maintains fuel level or not.

If it doesn't maintain, then you know the problem is with the fuel pump.

If it maintains, then the problem is the in fuel hose, primer bulb, tank vent, separator or even pick up tube. The next step will be to disconnect the now connected PGT hose from the primer bulb suction side. Disconnect the same with the in tank's primer bulb suction side and connect it to the still connected PGT's primer bulb suction side. In short, with this set up you know you are using a known working fuel pump and primer bulb and will be testing the pick up tube, separator and tank's vent.

If the clear fuel filter maintains correct fuel level with the preceding setup, then it's fair to conclude the primer bulb is faulty. If it doesn't, then you know the problem is either with the separator, pick up tube or tank vent. The separator can be isolated but before doing so check make sure your connections are oriented correctly. Contrary to popular belief, separator connections needs to be oriented correctly, i.e. inlet should be hose from fuel tank while the outlet should be hose going to the primer bulb. With the separator isolated, do a test run again. If it maintains correct fuel level (at the clear fuel filter) then you know the separator is clogged and needs to be corrected.

If it doesn't maintain, then the pick tube is clogged or the vent tank is clogged. The best way to do a quick fix is to blow back on the pick up tube with low pressure air (NO MORE THAN 10 PSI). Just make sure the gas tank cap is open. If air escapes the gas cap then you know it is not clogged. Do the same with the vent tube, blow back into it and if air escapes to the gas cap you know it is clear. CAUTION: MAKE SURE YOU HAVE THE PICK UP TUBE CAPPED OR CONNECTED TO THE PRIMER BULB WHEN YOU BLOW BACK INTO THE VENT TUBE AS FUEL CAN SPILL OUT OF THE PICK UP TUBE.
 

binghaml

Cadet
Joined
Mar 28, 2015
Messages
14
When you replace all the fuel lines... Did you replace the squeezy? also have you tried running off of a small tank?

I replaced the primer bulb with a mercury one when replacing the fuel lines. I have not tried a small tank yet.

Clear fuel filter is indispensible for troubleshooting fuel related problems especially with top speed related problems.

It has been saving me many trips to the lake and definitely giving me a "window" to look through to see what is going on..

At the moment I do not have a PGT. I just got back from working on the boat. I drained the gas, took off the fuel level sending unit and did not see any screen for the pickup. The inside of the tank looks pristine by the way, not one spec of discoloration even. I decided to take the pickup tube off, and it too was pristine with no blockages or anything (pics of it below). So at this point, I don't see how anything in the fuel tank can be causing the problem - there wasn't even a spec of dirt where it shouldn't have been. Given this new information, do you think that a PGT is still going to be useful? I'd like to avoid buying one if I can, but if it's necessary I'll do it.

It seems as though I can start traveling up the line and isolating things at this point, since the tank is clean and clear.

I sat down and figured out how "new" my water/fuel separator is - I have only filled the boat one time since I installed it. It's had less than 25 gallons of (fresh) fuel go through it, and the fuel tank is spotless. There's no water in the clear collection part on the bottom of the separator. I suppose it wouldn't be a waste for me to buy a replacement cartridge as I'll need one eventually anyway, but is there anything I'm missing that could have caused this to clog/fail so quickly, if it has?

Is a primer bulb likely to be faulty from the factory? The one on the boat (mercury brand) is less than 6 months old, just like all the fuel lines.

I took another look at the fuel pump (I've lost count how many times now), and the diaphragm was still nice and pliable with no holes or tears, though it does have more of a tendency to want to "roll up" when out of the fuel pump, than when it was new in the package. Can these be installed backwards? Obviously you can put the large side of it on the small part of the pump, but if you flipped it on the other axis, would it be backwards? I don't see anything showing what way it should be put on. Doesn't seem like it would matter, it's just a thin piece of rubber/compound material (I don't know exactly what it's made of). All the visible parts of the pump look fine to me. I have some pictures of it below.

I guess at this point I just need to know if my fuel tank is in fact good to go. With the inside being perfectly clean, along with the pickup tube, and no screen to be clogged, is it safe to rule it out?

Here's some pictures:

Don't mind the interior, I'm halfway done re-upholstering it (starting from the bow) ;)

Fuel pump:
39ZCUnz.jpg


Fuel pump diaphragm:
qpEtlO7.jpg


Inside fuel tank:
6BQ7GKL.jpg


Looking through pickup tube (no screen):
MmeN6Ws.jpg


Other end of pickup tube (90deg bend for brass fitting for hose to fit on):
ZLyKaXj.jpg


The brass fitting for fuel line to attach to fuel tank:
LHvHYuY.jpg
 

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,817
If the tank and the pick up tube are in perfect condition, then you are basically left with three items to troubleshoot, i.e. fuel pump, primer bulb and the separator. You can just by-pass the separator for now and see if that will fix the fuel delivery problem. If problem persists, then it is time to try another primer bulb (make sure it's connection are oriented properly) while continuing to by-pass the separator. If problem still persists then there is only one thing left to conclude, the fuel pump is not delivering the right amount of fuel.

In the pics of the fuel pump, you did not show the other side and I was wondering if you have the gasket also that goes with the diaphragm. Additionally, double check the fuel filter (screen) on top of the fuel pump to make sure it is there and clean.
 
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