Outboard Motor problem- Fuel Pump?

[brad9798]

Out in the skiff this weekend, and had to get towed in.

65-horse Suzuki outboard, three rebuilt carbs. (last year) new linkage, new A LOT of things (motor is 1987 model, and well maintained).

Going along at about 45mph and suddenly RPM's dropped to about idle, then went up and down every couple of seconds. So I dropped the throttle to idle, it worked fine, so I jumped it back up.

Then it just quit ...

First thought- Out of gas, but tank was just filled.

Second thought- air in fuel line, so I primed it again. Nothing.

I HATE outboards, for just this reason- they sometimes act funky for no apparent reason.

Could this be a fuel pump/line problem? I mean it was not even coming close to starting after it died. Not even the next day!

Any good outboard advice on this forum????

Paying somebody $85/hour to hunt and peck is not what I want to do.

Thanks, in advance.

Brad

[John Bell]

The first thing I'd check would be the fuel filter. Then I'd check for water in the fuel. It's easy to get a lot of condensation in gas tanks in boats.

I'd also check the fuel lines and connctions under the cowl. Loose or old hoses connections can suck air into the carb bowls.

Beyond that, I dunno.

JB

[Rich VanValkenburg]

Is there a manually opened/closed air vent on the fuel tank? Air in the fuel line from a cut? How 'bout a weak spot in the line that collapses the harder you suck fuel through? This could also be on the motor, downstream of the tank connection.

Rich

[Figment]

Brad,

I share your distaste for outboards. I recognize that they have their advantages, but I quickly lose patience with their quirks and qualms.

We had a similar problem a few years back with a 15horse johnson. like you, we were reluctant to let the motor sit and wait in line for a few weekends and then pay superprices for guesswork, so we took the "broadsword" approach and rebuilt the whole fuel-delivery system. rebuilt carb, replaced fuel tank, supply line, and all little hosey things (I'm big on highly technical terminology) within the motor itself, scrubbed everything we could get at with pipe cleaners, etc.... you say your carbs are recently rebuilt, so that's half the battle.

somewhere in the midst of all of that, the never-specifically-identified problem got fixed, and hasn't recurred since. it took one afternoon and I think a grand total of $75 (we bought a NICE fuel tank that time)including a 12pack of Harpoon IPA. we were back out fishing the next morning.

my bottom line: sometimes it's just not worth trying to troubleshoot these things. chainsaws cut butter just fine.

[ 08-19-2002, 03:28 PM: Message edited by: Sailortect ]

[ahp]

I once had a much smaller (5 hp) outboard which did a similiar thing. It ran ok at moderate throttle, but died in a few seconds when I went to full throttle, but would then restart easily.

The problem was cracked O-rings on the hose fittings to connect to the external gas tank. Apparently at full throttle I was sucking air. Replaced the O-rings and all was ok.

[Mr. Know It All]

Check the fuel filter, if there is gunk in it, replace the filter and the tank. Free outboard motor repair advise----> http://bbs.cartserver.com/bbs/a/1655/index.cgi
I've saved some money by going here first. Good Luck!
Peace----> Kevin in Ohio

[Ruaridh]

If you can pump the fuel line bulb, and hear the carbs filling up (the bulb should go hard if its working properly), but then it still won't start, your problem is either:
a) Not fuel at all but ignition or something worse (blown crank end seals etc)
b) Your motor's gulped a heap of water / dirt and all of the jets in the carbs are blocked again. (The carbs on the Suzi's are quite easy to strip and re-build).

If the carbs have got more dirt in them often one of the first symptoms is the float valves sticking, so gas will flood out when you pump the hand bulb.

If the motor will start after hand pumping but only run for a 'float full', its probably burst diagphrams or valves in the fuel pump. Again easy to change.

So follow this simple procedure....
Fill carbs by hand pumping.
Won't start....check sparks.
Sparks but still won't start....clean out carbs.
Still won't start...time to take it to someone who knows what they're doing!!!

BTW IMHO it's totally ridiculous that manufacturers supply outboards any larger than about 25hp without giving you a proper full size water separator / paper element type filter (like a diesel) - considering how much gas you put through them and how tiny the orifices in the carbs are. The little gauze-type filters under the engine cowl just can't cut it. We used to always fit large 'Racor' type units to any large outboards being used commercially, but the cheap and readily available 'CAV 296' units work just as well. Also, if your motor's an autolube, the odd bit of 2-stroke oil put in the gas from time to time does no harm and it keeps the float valves in the carbs moving freely and helps inhibit corrosion within the carbs which can happen if your motor lies a lot without getting used.

Hope this helps,
Ruaridh.

[ 08-20-2002, 04:10 AM: Message edited by: Ruaridh ]

[brad9798]

Thanks for all the insight ... I'll have a fun Friday, I'm sure!

Brad

[brad9798]

Well, the problem was the ignition for one thing. It was shorting. Thus, the starting problem is fixed.

But- that did not fix the up/down/up/down/up/down with the throttle problem.

So, we tested the compression ...

Cylinder 1- 120
Cylinders 2 & 3- 75 each.

Blown head gasket???

Any thoughts?

Brad

[Mac_Muz]

Sounds like a vacuum leak to me. Check the carb mounts for being tight... if you happen on a loose one, yank the carb and look at the mount and gaskets as they apply. I am not familar with this engine, but there does have to be a air tight seal there.. it seems you are getting unmetered air from some place.

If you see smaller lines made of rubber like materials that you believe are vacuum lines look at the ends especialy where they contact hot parts, for splits and cracks.

Also throttle plate shafts are sealed and these can wear so air can get thru...

One way to test is with a can of WD-40. This should be safe for the most part....

Remove the engine cover for good venting and work out doors..

Run the engine as best you can in the range of the problem, or just above that if it evens out.

Spray a bit at the intake and listen to the engine, so you will know what to look for (hear) when you find a place that does this in the hunting...

The hunting: Allow the engine to clear from that first spritz.... And move one to one carb.

Spray at the base plate, then at the throttle plate. Wait a bit each time as you must hear the leak change the rpm.

Move on to any vacuum lines, and do both ends of any you find....

Do each carb untill you hear a change in rpm.. When you hear a change in rpm, you have found that leak. Repair or stop up that leak and continue to test each carb one at a time, untill you have found all the vac leaks.... Then you can do what ever you need to for a real fix....

Since I don't know this engine at all, I can't be specific. Perhaps the distributor has a vac line, and perhaps there are plugged vac line tubes for synching the carbs as one. These would be capped off, or used depending.... The caps may be leaking if there are any caps. The lines may be leaking, and the mounts may be leaking, as well as the throttle plate shafts....

If you find something this way and need to ask feel free too, but attempt to describe well what you found.

Do not use anything other than WD-40.... Wipe up what you see wet after, and what you can't get will evaporate soon... WD-40 leaves no residue that will protect anything.... it is not a good and lasting coating as claimed, but is useful for some things..... But real lubrication is not one of them.... What this means here is that WD-40 will not cause a fire later.... Mac

[John Bell]

Originally posted by brad9798:

So, we tested the compression ...

Cylinder 1- 120
Cylinders 2 & 3- 75 each.

Blown head gasket???

Any thoughts?

BradNot good. Rings? Scuffed cylinders?

Not all outboards have removable heads, case in point is my '82 25HP Merc.

If it has a removable head, it's usually not a big deal to get it off and inspect the cylinders.

Good luck.