1991 4.3 V6 Mercruiser need help!

[natureschild88]

I bought a '91 Larson with a 4.3L V6 pushing an Alpha One last week. The hydraulic tilt was broken when I purchased the boat and I have fixed that. New problem: the motor struggles when I rev it above 1200 rpm then dies. The boat had 1/2 tank of gas from last summer in it. I topped it off with premium and added a Quicksilver fuel additive. The motor had no sort of fuel filter. I added a fuel/water separator hoping this would solve the problem. No luck.

The motor idles smooth as can be at 750 rpm. Still sounds good at 1000. As soon as I get above 1200 it struggles then dies. I removed the linkage at the 2 bbl carb and so I could run it in neutral and watch if it was getting fuel. Both jets in the carb are shooting in gas. Could this be a problem with the fuel pump? Does the carb need to be rebuilt? Again, the boat idles fine and I believe the motor has decent compression.

Any help is greatly appreciated. Thanks!!

 

[achris]

Re: 1991 4.3 V6 Mercruiser need help!

Sounds like the main jets in the carb may be clogged. Put a timing light on one of the spark plugs and watch it while you rev the engine until it dies. Does the timing light still flash all the way down? If it does, likely a fuel problem, and I'd be looking at the mains, especially if it's been running without a filter.. :facepalm:

BTW, there's a 'throttle only' position on your remote controls, you don't need to remove the throttle cable...

Chris........

 

[natureschild88]

Re: 1991 4.3 V6 Mercruiser need help!

Sounds like the main jets in the carb may be clogged. Put a timing light on one of the spark plugs and watch it while you rev the engine until it dies. Does the timing light still flash all the way down? If it does, likely a fuel problem, and I'd be looking at the mains, especially if it's been running without a filter.. :facepalm:

BTW, there's a 'throttle only' position on your remote controls, you don't need to remove the throttle cable...

Chris........

Chris, I'm aware of the throttle only position and disconnected the assembly at the carb so that I could open it and watch what was happening inside the carb (I dont have an extra set of hands to help throttle the engine while I look into the carb, and as soon as I give it gas it starts to die). Have a buddy with a timing light that will help me check it out this afternoon and see if that is the problem.

If the mains are the problem, is there a way I could clean them out on my own, or should I remove the carb and take it into a professional shop? I'm sure I have all the tools to get to it, but I've never disassembled a carb and don't want to get to a point where its taken apart and can't be put back together. How hard is it to clean my own jets?

Also, the boat has a plastic gas tank. I've heard that the ethanol gasoline used in California could potentially cause a slime/scum to build up inside the tank and maybe clog the carb. I've only had aluminum tanks in my previous boats, do I need the get one for this boat? Thanks again for the help!

 

[NHGuy]

Re: 1991 4.3 V6 Mercruiser need help!

If it's a quadrajet the main jets are right in the bottom of the fuel bowl. You can remove them with a screwrdriver and clean out their orifices and the tubes they feed. It's worth a try.
You will need to remove the carb from the motor. Disconnect the choke rod and drive in the accelerator pump fulcrum with a small punch. Remove the pump arm and the pump, raise the top section and pivot it 90 degrees around the choke lever til the bend will fit through the hole.Take off the top section. Clean the bowl, pull the jets & clean the passages they feed by blowing carb cleaner and air back through from the main (primary) nozzles. Once it's all back together if there is a further fuel problem, do a whole rebuild.
Or if that's too daunting, find a carb guy. If you decide to rebuild ,have your own carb redone. Don't swap for one that's done already, there are lots of Quadrajets out there and most are not an exact match for yours.

 

[Silvertip]

Re: 1991 4.3 V6 Mercruiser need help!

He said it's a two barrel carb. Go to the library and find a Chiltons or any other shop manual for a 60's - 70's Chevy anything. Rochester 2bbl carbs were common then and changed very little over the years. They are one of the simplest carbs on the planet. Most everyone has a cell phone camera these days, take pictures before you disassemble it.

 

[Don S]

Re: 1991 4.3 V6 Mercruiser need help!

Instead of using really old Chevy information which won't help, use the OEM service manual. Being a 91, you have a Mercarb, not a Rochester, Merc stopped using Rochester in the early to mid 80's.

Boatinfo - Mercruiser Service Manual nr. 7 - 1983-1993 - GM V6 Engines

 

[natureschild88]

Re: 1991 4.3 V6 Mercruiser need help!

Instead of using really old Chevy information which won't help, use the OEM service manual. Being a 91, you have a Mercarb, not a Rochester, Merc stopped using Rochester in the early to mid 80's.

Boatinfo - Mercruiser Service Manual nr. 7 - 1983-1993 - GM V6 Engines

I called my local carburetor shop (San Diego Carburetor) and explained to them the problem. These guys are good, my dad swears by them. The technician told me right away that he doesn't think its the carb, he thinks its the fuel pump.

I'm looking around for a replacement fuel pump and can't find an exact replacement Mercruiser pump. The only one I've found is a Sierra, and the reviews on it are utterly horrible. I've read 4 out of 5 reviews that say the pump is garbage and that Sierra acknowledges that the pump is faulty and gives the customers a full refund. I don't want to waste my time taking a chance with a pump that is known to fail. Where could I find an exact Mercruiser replacement?

Also, I'm learning that in '92 the 4.3 liter went from a Mechanical fuel pump to an electronic one. Would it be possible to install an electronic fuel pump on my motor or is this just a bad idea? If so, how would I do this? Thanks for the help.

 

[NHGuy]

Re: 1991 4.3 V6 Mercruiser need help!

duplicate

 

[NHGuy]

Re: 1991 4.3 V6 Mercruiser need help!

Maybe put a pressure gauge on the fuel supply and see if it falls below 5.5 psi.
Here's a pump, right from I boats, Mallory, not Sierra. Mallory Mechanical Fuel Pump 9-35424 - iboats
Good luck, sorry about going all q -jet geek before.

I also found a factory one, but I boats blocks the company that lists it, there must be some kind of non business stuff going on.
To find it just put "41141A 2" in your browser.

 

[natureschild88]

Re: 1991 4.3 V6 Mercruiser need help!

Maybe put a pressure gauge on the fuel supply and see if it falls below 5.5 psi.
Here's a pump, right from I boats, Mallory, not Sierra. Mallory Mechanical Fuel Pump 9-35424 - iboats
Good luck, sorry about going all q -jet geek before.

I also found a factory one, but I boats blocks the company that lists it, there must be some kind of non business stuff going on.
To find it just put "41141A 2" in your browser.

Thanks a ton NHGuy!!!

A quick question, how were you able to find these fuel pumps and match them up to my motor's fuel pump? The maker of my original pump is Carter, the part number is 0-2210, how can I make sure that these other fuel pumps are a direct replacement for mine? I've done google searches to try to match up other manufacturers replacements and couldn't find anything other than the Sierra pump or a 23 year old used pump off of another motor. I want to be sure that this will mount to my engine without problems before I order one. Thanks again for the help, I was getting worried I'd have to just cross my fingers and buy one of the faulty Sierra replacements on Amazon!

 

[jonny rotten]

Re: 1991 4.3 V6 Mercruiser need help!

I have the same motor same year and had the same problem with my boat.Would bog and backfire when I cot on it.Changed the fuel pump and it runs fine now.I had a carter pump also.I went with a mercruiser fuel pump.Probably wasted money and could have went aftermarket,but I figured its fuel and why take chances.Read the same reviews on the sierra,no thanks!If you take the fuel pump off there are numbers on the flange that can be cross referenced.my flange number is 6031510b10.I would think yours is the same.REMEMBER WHICH WAY THE BODY IS MOUNTED UP OR DOWN.i had mine off before the mechanic showed up and he put it on upside down.I have a tight engine compartment and tried 3 hours to get it on before I quit and hired someone.Good luck

 

[NHGuy]

Re: 1991 4.3 V6 Mercruiser need help!

I got the part # by going to the Mercury Marine web parts page...https://webapps.brunswick.com/literature/literatureSearch.do
found the 2 bbl 4.3 V6 and went to the fuel pump page where the part # was found.
I keep that Mercury parts catalog in my bookmarks bar.
The Sierra was just sitting in the I boats parts list. I put in 1991 4.3V6 2bbl and there it was.
BTW I just put "Carter 0-2210" in Google and got a hit too.
I'd try to get the OE one "41141A 2" .

 

[natureschild88]

Re: 1991 4.3 V6 Mercruiser need help!

Johnny Rotten, I feel much more happy that I'm replacing the fuel pump now, thanks for the input. My engine has a very tight compartment as well and I can tell it's going to be fun trying to put in the new pump. I'll try it myself first and see if I can save money versus having a mechanic do it.

NHGuy, thanks again for all the help. I ended up contacting a local Mercruiser dealer and sure enough, they were able to find me a direct replacement part. I figure if the original fuel pump lasted 22 years until it went out, why not get another exact replacement. Its a little more expensive than the Mallory and Sierra, but I can install it with confidence. I also went with the dealer because they will have it for me tomorrow, meaning I can put the boat back in the water by Saturday... If I'm quick, maybe even a Friday evening wakeboard/fishing session?? Haha, thanks a lot again for all the help. I'll let you guys know how she runs after I get the new pump installed.

 

[Bondo]

Re: 1991 4.3 V6 Mercruiser need help!

Johnny Rotten, I feel much more happy that I'm replacing the fuel pump now, thanks for the input. My engine has a very tight compartment as well and I can tell it's going to be fun trying to put in the new pump. I'll try it myself first and see if I can save money versus having a mechanic do it.

NHGuy, thanks again for all the help. I ended up contacting a local Mercruiser dealer and sure enough, they were able to find me a direct replacement part. I figure if the original fuel pump lasted 22 years until it went out, why not get another exact replacement. Its a little more expensive than the Mallory and Sierra, but I can install it with confidence. I also went with the dealer because they will have it for me tomorrow, meaning I can put the boat back in the water by Saturday... If I'm quick, maybe even a Friday evening wakeboard/fishing session?? Haha, thanks a lot again for all the help. I'll let you guys know how she runs after I get the new pump installed.

Ayuh,.... Welcome Aboard,... I'm not Exactly Sure, But,.....

I believe on the front face of yer block, directly in line with the fuel pump push rod, is a bolt hole, which may, or may not have a bolt in it,...

If it Does have a bolt in it, take it Out,... it'll be a pretty short bolt,...
Get a Longer 3/8"- 16 bolt, 'n screw it in til it bottoms out,...
It'll run up against the fuel pump push rod, snug it lightly, 'n when ya pull the pump,...
The push rod won't fall down into the pocket,...

Good Luck,...

 

[jonny rotten]

Re: 1991 4.3 V6 Mercruiser need help!

Ayuh,.... Welcome Aboard,... I'm not Exactly Sure, But,.....

I believe on the front face of yer block, directly in line with the fuel pump push rod, is a bolt hole, which may, or may not have a bolt in it,...

If it Does have a bolt in it, take it Out,... it'll be a pretty short bolt,...
Get a Longer 3/8"- 16 bolt, 'n screw it in til it bottoms out,...
It'll run up against the fuel pump push rod, snug it lightly, 'n when ya pull the pump,...
The push rod won't fall down into the pocket,...

Good Luck,...

Man do I wish I knew this..........Im goin out and checkin

 

[Don S]

Re: 1991 4.3 V6 Mercruiser need help!

Don't even think about using a wrench to snug that bolt against the pump rod. The bolt only has to barely touch the rod to hold it from falling. If you score the push rod, then you do have a problem.

 

[natureschild88]

Re: 1991 4.3 V6 Mercruiser need help!

Ayuh,.... Welcome Aboard,... I'm not Exactly Sure, But,.....

I believe on the front face of yer block, directly in line with the fuel pump push rod, is a bolt hole, which may, or may not have a bolt in it,...

If it Does have a bolt in it, take it Out,... it'll be a pretty short bolt,...
Get a Longer 3/8"- 16 bolt, 'n screw it in til it bottoms out,...
It'll run up against the fuel pump push rod, snug it lightly, 'n when ya pull the pump,...
The push rod won't fall down into the pocket,...

Good Luck,...

Thanks Bond-O, I watched a few youtube videos on guys replacing fuel pumps on cars, they had to jimmy screwdrivers into the hole to hold up the plunger to keep it in position. Looked like a headache, seeing that my motor is very cramped for space as it is where the fuel pump is located.

Found these two holes, I'm guessing you are referring to the top hole? There was not a bolt in it, but when I shined a flashlight and looked down the bolt hole I could see that it went fairly deep. Is this the hole you are referring to? Thanks a lot by the way. Here's a couple pics of what I'm lookin at

 

[Bondo]

Re: 1991 4.3 V6 Mercruiser need help!

Thanks Bond-O, I watched a few youtube videos on guys replacing fuel pumps on cars, they had to jimmy screwdrivers into the hole to hold up the plunger to keep it in position. Looked like a headache, seeing that my motor is very cramped for space as it is where the fuel pump is located.

Found these two holes, I'm guessing you are referring to the top hole? There was not a bolt in it, but when I shined a flashlight and looked down the bolt hole I could see that it went fairly deep. Is this the hole you are referring to? Thanks a lot by the way. Here's a couple pics of what I'm lookin at

View attachment 202942View attachment 202943

Ayuh,... You got it buckeroo,...

Like Don said, run 'er in Gently,...

 

[natureschild88]

Re: 1991 4.3 V6 Mercruiser need help!

Finally put in the new fuel pump yesterday. My motor did not have the hole in the block to drive in a bolt that would hold the cam in place. A hole was present, but it did not pass all the way through to the cam. I was able to hold the cam up with my finger and quickly slide in the new pump before it fell back down. I noticed that the pump wouldn't mount all the way to the motor if the cam slid down, I got it to mount flush, so I believe I installed it properly... But problem not solved

I disassembled the old fuel pump... Inside of the housing (where the spring is with the rubber plunger) it had about 2 or 3 tablespoons of corrosion built up that poured out when I opened it up. But everything still appeared to be in running shape. In any case, still probably a good thing that I replaced it, the spring was wearing very thin and was on its way out.

The engine is doing the same thing: Running fine at idle up to 1000 RPMs and then cuts out when I try to run it faster. I'm going to put a fuel pressure gauge in line tomorrow to see how much psi the pump is actually pulling. If pressure looks good I'm going to remove the carb and take it to the shop to see if it is indeed a carb problem after all. Kind of bummed, I was really excited and thought that new fuel pump would solve the problem.

 

[natureschild88]

Re: 1991 4.3 V6 Mercruiser need help!

Finally fixed it!!!

I was getting real close to removing the carb and sending it to the shop for a rebuild. I've heard the horror stories of guys disassembling carbs and not being able to put them back together. I decided to go for it anyway.

Before I did anything, I figured I'd check the basics to make sure it wasn't something stupid. First checked all of the plug wires and plugs. All spark plugs were tight, all plug wires were pushed in all of the way. At that point I opened up the carb. I did not disconnect it from the manifold, I just removed the upper half.

Glad I didn't take it in for a rebuild, it looked like it had already recently had one! The accelerator pump, float, and gaskets all looked new on the inside. I went on and removed the jets on top with all of the different ports. Half of them were closed up with debris!! I guess this is from the ethanol in today's gas. I boiled the jets in a mixture of water and vinegar for 7 minutes. Then pulled it out and blew every port with a can of carb cleaner. Looked much better. I then removed the 2 smaller jets that sit next to each other toward the bottom. One looked fine. The other was clogged shut! Sprayed both of them out with carb cleaner until they were clear. Put everything back together. Luckily, I took lots of pictures while I disassembled it. Helped a lot when I put the linkage back together.

Finally took apart the small filter where the gas first enters the carb. Half of it was clogged shut. Sprayed with carb cleaner, looks like new.

Put everything back together and threw on the muffs. Took a little while to fire up, but finally got the gas back into it and it turned over. I let it idle for 30 seconds... Everything normal... Finally gassed it.. and... IT LIVES!!! Gonna polish it all up and get to the launching ramp right now!! Just in time for some Friday evening wakeboarding/fishing

Thanks a lot to everybody for all the additional help!!