1984 9.9 Evinrude starves for fuel

kbait · Jun 25, 2013

This motor now has a 15hp carb and apparently ran fine after carb install. Brought to me needing choke to run.. I assumed a partially clogged main jet. Pulled carb and jet was clear (cleaned w/thin wire anyway and blew out). Rest of carb clean/low speed passages clear, float level when inverted. New needle retainer installed, and new fuel line pump/carb. Fired it up in a barrel, and it still needs choke-bump to keep running. Fuel pump good/fresh fuel. Pumps water from indicator fine, and out exhaust port when thermostat opens after a minute from cold start. One strange thing.. at anything over low idle, exhaust bubbles out of prop (barrel testing). In my experience, you have to get 'em revving pretty good to have enough exhaust pressure to overcome the leakage that comes out of the exhaust relief port above water. I'm wondering if this behavior is indicative of a different problem. Oh, and the exhaust chamber drain port near gearcase is clear..water drains normally when motor pulled from barrel.

Any ideas before pulling/cleaning carb again? I'll also try to see if the reeds are closing.. kinda hard to see on these motors, and I don't really want to remove powerhead to remove reed plate (if that's even the issue).

Feel like I'm missing something w/the exhaust bubbling from the prop like that..

Thanks!

fireman57 · Jun 25, 2013

Re: 1984 9.9 Evinrude starves for fuel

The bubbles are normal on my '76 9.9. You might pull the carb and use a flashlight to look into the reed valves. Sometimes a stray bolt somehow finds it's way in there. If it was 15 carb it would have bigger jets which would lead to flooding rather than starving I would think.

kbait · Jun 25, 2013

Re: 1984 9.9 Evinrude starves for fuel

Agreed. I checked the jet.. it is indeed a jet for a 15, to match the 15 carb. I put it together again and same deal.. starves at anything slower than full idle in neutral. I'm thinking reeds too. Looked in when carb was off, but you can only kinda see one valve. Looks like powerhead removal to check it out.

Is it possible for a crank seal to make it act like this?

Thanks.

OptsyEagle · Jun 25, 2013

Re: 1984 9.9 Evinrude starves for fuel

Do you still have the old 9.9Hp carb? If I had that and I was going to pull the current one I would certainly want to try it to see if the problem goes away. I am always a little weary of a carb change. I know many do it but I would think that there would be exhaust issues as well as timing advance issues when only the carb is changed.

kbait · Jun 25, 2013

Re: 1984 9.9 Evinrude starves for fuel

That's a good idea if something's actually wrong w/this 15hp carb, but it all looks good. I've put 15 carbs on other 9.9's (one '81, one '85) and they worked flawlessly. But I like the thinking of trying the known good 9.9 carb before pulling the powerhead.

I still don't think it's a carb issue. It'll stay running at high idle in neutral, and I can get response from the low speed needle, and the main jet is clear and no leaks in any carb plugs. It'll starve for fuel at anything lower than high idle, and needs a choke bump to keep running. I'm thinking it's probably not reeds, as what are the odds of both sides failing at once? It should run fine on one cylinder if something was blocking one side's reed from closing.

I've never had crank seal issues on any of the motors I've worked on. Would a leaky crank seal lessen the crankcase pressure/vacuum enough to cause the reeds to not function correctly at low rpms? I would think any crankcase leak could cause this issue. I'll probably spray some carb cleaner around the block/carb when it's running and see if it changes anything.

Hoping someone checks out this thread and says 'yep, I been there..'

fireman57 · Jun 25, 2013

Re: 1984 9.9 Evinrude starves for fuel

Have you checked spark to see if it's running on one cylinder? I know it shouldn't pick up by bumping the choke if it is but it could be a combination of things.

kbait · Jun 25, 2013

Re: 1984 9.9 Evinrude starves for fuel

Compression and spark are tested good. New QL77JC4's gapped to .030". It's definitely running on both cylinders, and starves both cylinders at anything lower than high idle.

fireman57 · Jun 25, 2013

Re: 1984 9.9 Evinrude starves for fuel

Have you tried running it with a different fuel line and tank? Could be a restriction in one of them.
Tried pumping the primer bulb to keep it going instead of bumping the choke? I know you said the fuel pump was good but if it is weak this will tell you.

OptsyEagle · Jun 25, 2013

Re: 1984 9.9 Evinrude starves for fuel

kbait said:
I've never had crank seal issues on any of the motors I've worked on. Would a leaky crank seal lessen the crankcase pressure/vacuum enough to cause the reeds to not function correctly at low rpms? I would think any crankcase leak could cause this issue. I'll probably spray some carb cleaner around the block/carb when it's running and see if it changes anything.

Hoping someone checks out this thread and says 'yep, I been there..'

I have been there on a crankcase seal leak and all it did was make the one cylinder that had the bad seal run weak, and even then the cylinder still ran, just not enough to run by itself. Now I suppose there are worse seal leaks then the one I had. My seal was the bottom cylinder and the spring was completely snapped but the rubber was still there. I imagine it was still getting some seal.

In any event, I would think that both seals would need to go before you would see a problem like yours.

Now here I am just throwing things out there. Is the carb roller linked with the timing advance correctly and where is the carb's slow speed adjustment currently set to? How many turns out from seated?

kbait · Jun 26, 2013

Re: 1984 9.9 Evinrude starves for fuel

Fireman57: I'm using a known/good testing fuel tank with 50/1 non-ethanol mix. Bulb stays full as normal when testing.
Optsy: Nice info on the crank seals. Kinda like my thoughts on the reeds.. both would have to go out to not run at all. Link/sync is all good.. cam follower right at cam mark when butterfly begins to open. Low speed adjustment at about 1.25 turns at start of testing.. at high idle it's about right (dies off at leaner setting, too rich if more open). It won't idle at that setting (just high idle in neutral), and I've tried richer settings to try to get enough fuel for slower idle.. up to 3 or 4 turns open. Just seems to not have the suction to pull fuel in at anything less than high idle. Must be either reeds or crankcase leak in my opinion. I'll try starting it later today and spray carb cleaner all around and see if it changes things. I'll post back, and please reply if you've seen this particular issue. Thanks for the thoughts so far!

kbait · Jun 26, 2013

Re: 1984 9.9 Evinrude starves for fuel

Another thought: I pulled the motor from the barrel yesterday and set on a stand.. water drained from port near gearcase as it should. This morning I needed that stand and layed the motor down on it's back on the floor, and about a quart of water came out from the water intake holes in gearcase, and also from the exhaust relief port higher up. I KNOW this isn't normal. I'm thinking it has something to do w/motor 'bubbling' exhaust from the prop at anything above low idle, AND may have something to do w/exhaust back pressure, which could affect crankcase pressure/vacuum and cause the motor to not run w/o choke below high idle. I'm going to think on this, and if anyone has an opinion, please chime in! Thanks

fireman57 · Jun 26, 2013

Re: 1984 9.9 Evinrude starves for fuel

Your last post may be the problem, especially with too much back pressure. Is the vacuum line in good shape and hooked up?

OptsyEagle · Jun 26, 2013

Re: 1984 9.9 Evinrude starves for fuel

I agree that a quart of water is not normal when it basically should have flowed right out of that cavity the minute you pulled the motor from the barrel. It sounds like you might have something stuck right in that exhaust chamber preventing the water from flowing out. Since the majority of the exhaust should go down there as well, if you did, I cannot imagine you not having problems. Kind of like a banana in the tail pipe. What I don't understand, if this is the case, is why choking it would give it any relief and also how a banana or anything else would ever get in there. If there is something it must be sealed tight since you said that it sat on the stand upright for the entire evening and the water didn't drain out. That exhaust tube would probably only hold a little over a quart of water if someone sealed up the bottom.

I added some pictures I was looking at of my 15Hp (1976) that should be built pretty similar to yours, to verify that the water/exhaust cavity should be pretty clear and not really want to hold any water, under normal conditions.

kbait · Jun 26, 2013

Re: 1984 9.9 Evinrude starves for fuel

Thanks Guys. I think there's something fishy going on as exhaust chamber water drains, but not completely when upright. I'm going to fire it up again and spray some carb cleaner around the carb/reed plate/powerhead and see if I can detect a leak. I don't think I will.. then pull lower unit and find the banana!

I'll post back after checking it out. Thanks again!

OptsyEagle · Jun 26, 2013

Re: 1984 9.9 Evinrude starves for fuel

Take a visual look inside the propeller. Maybe some mud got in there and cemented itself all up ... or a banana.

kbait · Jun 26, 2013

Re: 1984 9.9 Evinrude starves for fuel

Prop ports are clear, can shine light into chamber behind.. no bananas..

kbait · Jun 27, 2013

Re: 1984 9.9 Evinrude starves for fuel

So, I put the original 9.9 carb back on.. Runs flawlessly. Put the 15 carb right back on, and it also works flawlessly. No idea why it idles fine now. Still does the weird drain thing when layed down, but I'm not one to argue w/success..

Thanks to all for the suggestions!

the machinist · Jun 27, 2013

Re: 1984 9.9 Evinrude starves for fuel

I would guess there was a slight air leak at the carb/mainfold gasket. As for the retention of water, suspect someone used the tall (long shaft) water pump outlet grommet & it is sealing the drain hole around the water tube.

kbait · Jun 29, 2013

Re: 1984 9.9 Evinrude starves for fuel

Thanks LeeRoy! And thank you VERY MUCH for your ramblings site.. Awesome resource!!

Welcome to LeeRoy's Ramblings

1984 9.9 Evinrude starves for fuel

Commander

Captain

Commander

Lieutenant

Commander

Captain

Commander

Captain

Lieutenant

Commander

Commander

Captain

Lieutenant

Attachments

Commander

Lieutenant

Commander

Commander

Senior Chief Petty Officer

Commander