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1998 bf15aw

D

Darkshark

New member
Hello all! 1998 Bf15aw BAAS-1300059

I've read many many threads on different issues I've managed to fix with your help! So thanks for that!


Okay now for the issue at hand! This motor starts great, idles great, and runs great. But only with the "vacuum hose" detached from the mesh air filter attached to the carb. If left on without a clip (a clip that it originally does not have from the factory) it will build pressure and pop off with a huge sound of rapid air pressure release and then continue to work properly while detached. However if you force it to stay on with a clip(again no clamps/clips are meant to be on this particular air hose) the motor will not draw gas, and will only continue to run if you manually pump the primer bulb. What gives?

I had an old Acura Vigor that had the exact issue this outboard is having with a vacuum hose, that if left off would run great and so I just left it off indefinitely and never had a problem. Will this be a similar story?

P.S.
Just in case it helps, it does seldomly randomly rev higher than I'm holding the throttle, and just yesterday it wouldn't go over 5 knots with the throttle fully engaged, which I've chalked up to an old fuel filter which I'll be replacing tomorrow when it arrives, along with re-cleaning the carb again, and installing new spark plugs.

Thanks for reading!!
 
Hi,

That hose comes from your crankcase vent. See items 5, 6, 7, 8, 9 in the link below:

It is not a vacuum line. It is intended to allow crankcase gasses to enter the engine intake and have them mix with the fuel/air mixture and burn in the cylinders..An early form of emissions control if you will.


I suspect that the filter screen (item 7) is clogged and, possibly, the stopper valve (item.9) is stuck due to carbon build up.

As a result, excessive pressure is building in the crankcase and blowing that hose off.

And....that might be a good thing because excessive pressure in there can cause the crankshaft seals to leak badly and fail.

The vent valve assembly should be disassembled and cleaned/repaired.

HOWEVER....the parts are no longer available!

So, if you do try to clean it up, you need to use extreme care not to damage anything.

It is my opinion that it can be easily done but the cover gasket probably won't survive disassembly.

I wouldn't let that stop me as I am confident that I can make my own gasket with gasket material from the auto parts store or, if it's a rubber gasket, with some properly applied gasket maker.

I would first apply PB Blaster or Kroil to the bolts and let sit a couple of days before attempting to loosen the bolts.

I would then apply heat from a heat gun or hair dryer set on high. Give the bolt heads a couple of light raps/taps with a small hammer before trying to break them free. You don't want to break them off in the head or, worse, crack the thread boss. They haven't been moved for a VERY long time!

Or....
You could choose to just leave the hose off as you did with the Acura. It's not right, I don't like it, it will, after a time, have engine oil spraying on to the engine
....BUT..it's waaaay better than having the crankcase always over presserized.
A better option would be to find a longer piece of hose and route it outside the bottom of the oil case. There are should be several places to do that. It will eventually make a mess on the outside but you can wipe that off.

Good luck.
 
jgmo said:
Hi,

That hose comes from your crankcase vent. See items 5, 6, 7, 8, 9 in the link below:

It is not a vacuum line. It is intended to allow crankcase gasses to enter the engine intake and have them mix with the fuel/air mixture and burn in the cylinders..An early form of emissions control if you will.


I suspect that the filter screen (item 7) is clogged and, possibly, the stopper valve (item.9) is stuck due to carbon build up.

As a result, excessive pressure is building in the crankcase and blowing that hose off.

And....that might be a good thing because excessive pressure in there can cause the crankshaft seals to leak badly and fail.

The vent valve assembly should be disassembled and cleaned/repaired.

HOWEVER....the parts are no longer available!

So, if you do try to clean it up, you need to use extreme care not to damage anything.

It is my opinion that it can be easily done but the cover gasket probably won't survive disassembly.

I wouldn't let that stop me as I am confident that I can make my own gasket with gasket material from the auto parts store or, if it's a rubber gasket, with some properly applied gasket maker.

I would first apply PB Blaster or Kroil to the bolts and let sit a couple of days before attempting to loosen the bolts.

I would then apply heat from a heat gun or hair dryer set on high. Give the bolt heads a couple of light raps/taps with a small hammer before trying to break them free. You don't want to break them off in the head or, worse, crack the thread boss. They haven't been moved for a VERY long time!

Or....
You could choose to just leave the hose off as you did with the Acura. It's not right, I don't like it, it will, after a time, have engine oil spraying on to the engine
....BUT..it's waaaay better than having the crankcase always over presserized.
A better option would be to find a longer piece of hose and route it outside the bottom of the oil case. There are should be several places to do that. It will eventually make a mess on the outside but you can wipe that off.

Good luck.
Click to expand...
Wow thank you for the swift, honest, and detailed response!

This is my first time working on gas motors of any kind so I'm not confident I can take that thing apart without messing anything up if it's that easy to mess up lol! I am however off to a good start because it wasn't running when I received it at all.

Do you think that issue has anything to do with the p.s. issue I just recently ran into? Do you think I'm on the right track in trying to fix that new issue?

Thank you again for the awesome response!
 
Well, I was agreeing with you about replacing the filter and maybe trying to clean the carb again. That's likely to solve the loss of power you experienced.

It might also cure the engine speed increase you mentioned as a lean condition might occasionally cause something like that. Although, I would really only expect that in neutral, not under load. So, that's to be seen.

Address the vent issue as you wish and then follow through with your plan to change out the fuel filter and see if you get some improvement.

Another possibility, of course, is the fuel pump. One that old could be failing.

Because that pump is a diaphragm type that's driven by the camshaft, you will want to make dang sure that it isn't leaking gas into the engine oil.

The diaphragm is a serviceable part and is probably the only thing still available for that pump. $30 at boats.net.

If at all in doubt, change it out.

Item 2 in the link:


Good luck.
 
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