4.3 OMC Suddenly started acting like its out of gas

[Too Fast]

I have a 1987 OMC 4.3 on a MFB Hull. I just bought it a couple weeks ago. I took it out last weekend for the first time since de-winterizing it. It ran like a CHAMP!! No problems at all. I ran it for a couple hours out on the river full throttle with no issues. Parked it. I put some STABL Ethynol treatment in it. Started up today with the muffs in the driveway... ran fine. Got back out to the river, started up fine, idles fine, but now when i take off it acts like its out of fuel.If i punch it, it WILL go but will start acting like its out of fuel in a few seconds. Low idle is fine, a lil rocky. Here is what I know; I took the fuel filter off after i got it back to the dock(NEW FILTER), it was only 3/4 of the way full of fuel, it should have spilled out full of fuel.There was no water in the filter. So I pulled the valve off the top of the fuel tank (i guess thats called the "pick up"?) It was just a straight line one, I bought an anti sifen one to install (will do tmaro). I also replaced the lil fuel filter on the carb. I am really baffled cause of the fact that it ran and sounded beautiful last week, I was super impressed with it. Now its running like poo.
ANY IDEAS ANYONE????

 

[JJBoatr]

Re: 4.3 OMC Suddenly started acting like its out of gas

This is kind of tough to diagnose without knowing what type of fuel delivery and ignition system you have, but if you have a carb here goes. Have you disconnected the fuel line from the carb? I had a similar problem on my boat last year. Initially I had some bad gas, but after flushing out the system it still ran like crap above idle. I found a small piece of gasket obstructing my fuel inlet passage on the carb restricting fuel flow to the bowl. This obstruction prevented the bowl from refilling quick enough to keep up with the engines demand. Have you had the carb apart? Sounds like your acceleration pump is working but your main jets aren't delivering enough fuel after that initial shot. If the carb turns out to be fine another good place to look would be your ignition components, check for corrosion in the cap, cracks in plug wires etc. Be careful trusting your engines performance on the boots while troubleshooting a problem like this. Revving in the driveway and full throttle acceleration on the water are totally different animals concerning your engine and how it reacts.

 

[Too Fast]

Re: 4.3 OMC Suddenly started acting like its out of gas

Yah I have a two barrel carb. The distributor cap and wires look brand new. They guy I bought the boat from said he was a mechanic and that he did all the services last fall. Its just very odd that it started doing this out of the blue. The valve that I mentioned, is that the "pick up"? Shouldnt there have been more fuel in the filter when I pulled it off? Its one of those fuel filters that look like oil filters so it should have been full. Fuel Pump??

 

[Art Bernard]

Re: 4.3 OMC Suddenly started acting like its out of gas

Did the guy you bought it from run it with non-ethanol gas? Ethanol will clean all the crap out of your tank and fuel lines and unfortunatley allot of it will wind up in your carbs filter or not. I had an issue with this once and since than I go to great effort to keep my tank and lines clean. Haven't had a problem since. Bad thing is that if crud has gotten into your carbs it can cause allot of problems. Look into the electrical stuff, but I would recomend inspecting your fuel tank and cleaning if nessairy, replace your fuel lines, filters, and get your carbs cleaned. Once your stuff is cleaned or new, ethanol really isn't a problem unless you let it sit in your tank to long.

Art

 

[HT32BSX115]

Re: 4.3 OMC Suddenly started acting like its out of gas

There was no water in the filter. So I pulled the valve off the top of the fuel tank (i guess thats called the "pick up"?) It was just a straight line one, I bought an anti sifen one to install (will do tmaro). I also replaced the lil fuel filter on the carb.

Howdy and welcome aboard!

You're on the right track so far.....

Filters & anti-siphon valve are a good start.

You also may have a plugged fuel pick-up (inside the tank)

It's a little screen at the bottom of the tank to prevent the big stuff from making it to your anti-siphon valve and filters.

The best way to diagnose that is to get a small fuel tank and connect it to the fuel line from your tank and see if that helps. If it "fixes" it, you probably have a plugged pickup or a possibly a plugged vent.

Also check your fuel pump. (look for evidence fuel in the clear hose from the fuel pump to the carb air inlet and/or an odor of fuel in the oil)

If you don't know how old the fuel is, drain most of it and refill with fresh gasoline. Use what you drain a a few gallons at a time until it's used up

Regards,


Rick

 

[Too Fast]

Re: 4.3 OMC Suddenly started acting like its out of gas

Howdy and welcome aboard!

You're on the right track so far.....

Filters & anti-siphon valve are a good start.

You also may have a plugged fuel pick-up (inside the tank)

It's a little screen at the bottom of the tank to prevent the big stuff from making it to your anti-siphon valve and filters.

The best way to diagnose that is to get a small fuel tank and connect it to the fuel line from your tank and see if that helps. If it "fixes" it, you probably have a plugged pickup or a possibly a plugged vent.

Also check your fuel pump. (look for evidence fuel in the clear hose from the fuel pump to the carb air inlet and/or an odor of fuel in the oil)

If you don't know how old the fuel is, drain most of it and refill with fresh gasoline. Use what you drain a a few gallons at a time until it's used up

Regards,


Rick

Rick, Thanks, this sounds like a good place for me to start checking next. I will post again later today with the results.

 

[Too Fast]

Re: 4.3 OMC Suddenly started acting like its out of gas

Ok, So today i replaced the anti-siphon valve and filters. Same symptoms. symptoms are the same with the muffs and when on the lake. Once it hits about 1800 rpm and up it just misses every couple seconds or so..........It will maintain the rpms it just misses. I pulled the plugs and none are fowled or anything. wires look good. cap look good. I did notice that the rotors metal contact only "looked" like it was making contact with the corner of the contact. I think this, because it was only shiny at the corner> the rest of the contact appeared untouched. How much of that contact should there be? It only seemed to be about an 1/8" there if that. Open for ideas......

 

[Too Fast]

Re: 4.3 OMC Suddenly started acting like its out of gas

Just bought new plugs. There was ac delco plugs in it and ium replacing them with Champion plugs. Also putting a cap and rotor tune up kit on today. Will update later today.

 

[HT32BSX115]

Re: 4.3 OMC Suddenly started acting like its out of gas

It's beginning to sound like an ignition problem...... make sure your plug wires are in good condx and the advance is working right in the dist and the points, condensor etc are good/adjusted (or new)

 

[Too Fast]

Re: 4.3 OMC Suddenly started acting like its out of gas

It's beginning to sound like an ignition problem...... make sure your plug wires are in good condx and the advance is working right in the dist and the points, condensor etc are good/adjusted (or new)

Ok, its fixed the the problem, its not missing anymore YEAH!!! However, Now once I hit 2800 rpms the engine starts shaking and chugging and wont acheive 3K rpms. Kinda acts like a timing issue on a car. OH YAH DID I MENTION THIS IS MY FIRST BOAT? Im learning as I go. I replaced those components inside the distributor (i dont know what they are called). The tune up package didnt include any literature on what was what. I hope this is an alignment issue......

Also I did have a peice left over from the tune up kit. I couldnt figure out what it was or where it went cause i didnt see one on it already. I attached a pic the peice circled is what was left over. What is it?

 

[Too Fast]

Re: 4.3 OMC Suddenly started acting like its out of gas

PLEASE anyone have any advice. I have to have this thing running by next weekend. I got a camp site reserved on an island in upstate NY, can only get there by boat. Im reading a lot of things about dwell and gap, and timing. I dont have a clue what these things are. I can do timing on a car.

 

[Joshua Nichols]

Re: 4.3 OMC Suddenly started acting like its out of gas

I can do timing on a car.

Then you can time a I/O

Dwell angle, a term used in automotive context, indicating the degrees of rotation of the distributor cam during which the ignition contact breaker points in the distributor are closed
Gotta love online dictionary

You need a dwell meter to set it.. Point gap will get ya in the ball park. Then you adjust the dwell.. Set the timing.. Check the dwell again.. Yeah lots of fun.. The extra part you are worried about.. I think the is a strap to hold down the condenser.. I am not 100% sure

http://www.ehow.com/how_5366229_use-dwell-tachometer.html

 

[Joshua Nichols]

Re: 4.3 OMC Suddenly started acting like its out of gas

Wow check this out.. Didn't even have to hunt for this info... Right here at the top of the page....http://forums.iboats.com/showthread.php?t=335302

That help?

 

[Too Fast]

Re: 4.3 OMC Suddenly started acting like its out of gas

Thats great thanks. I will give it a shot. I got to go get a dwell meter first. I will update later.

 

[Joshua Nichols]

Re: 4.3 OMC Suddenly started acting like its out of gas

I found a awesome one on ebay.. It has a built in starter button.. I never use that part.. Found it on E Bay for dirt.. You can spend extra for a digital one..

This one works good for 10 bucks plus shipping and came in it original 30 year old box.. I opened it.. Looked brand new

 

[Too Fast]

Re: 4.3 OMC Suddenly started acting like its out of gas

OK, I figured out the problem. I didnt put the tension spring (the missing partin photo above) on the points assembly. Problem solved!!! Now I know!! lol. I checked the timing and its just a hair off the mark, not much at all.