Crud in carburetor, is it a problem?

[ronaldreagan]

My boat pings and back fires during acceleration but it idles fine. When I can get it on plane, it's 10 mph (25 vs 35 mph) slower than before having problems. It's a 2004 mercruiser 3.0 with 180 hours.

Could this crud in my carburetor be the problem?

Any tips on cleaning and rebuilding it?

 

[Scott Danforth]

yes. clean your carb, clean the inlet filter, and check your fuel if there is water in it.

 

[achris]

Yes, crud in the carb isn't good, clean it out. But your problems are timing related, not crud in the carb..

Chris...

 

[ronaldreagan]

yes. clean your carb, clean the inlet filter, and check your fuel if there is water in it.

I am concerned about water in the gas. I drained the tank and filled it with premium. Still had the problems. What is the best way to make sure no water gets in the fuel?

 

[Bondo]

I am concerned about water in the gas. I drained the tank and filled it with premium. Still had the problems. What is the best way to make sure no water gets in the fuel?

Ayuh,...... By addin' a canister type fuel filter ahead of the fuel pump,......

 

[ronaldreagan]

G

 

[ronaldreagan]

Yes, crud in the carb isn't good, clean it out. But your problems are timing related, not crud in the carb..

Chris...

I adjusted the timing to exactly the spec and slight made adjustments on the water to try and work out the problem. Absolutely not a timing adjustment problem. Tested all the ignition parts per the service, they check out. Asked around about the ignition module possiblity not advancing correctly, was told ignition modules either work or they don't, no in-between. Checked the timing advance curve at a few rpms, it seems okay too.

 

[nola mike]

Water in the tank can absolutely do that. Also if that crud in the carb is in the right place, you can be running lean with those symptoms. I'd start by either running off a jerry can and/or disconnecting your fuel line at the carb and run it into a container to see what your gas looks like. Assuming you don't have a water/fuel separating filter?

Edit: missed that the tank was already drained.

 

[ronaldreagan]

Water in the tank can absolutely do that. Also if that crud in the carb is in the right place, you can be running lean with those symptoms. I'd start by either running off a jerry can and/or disconnecting your fuel line at the carb and run it into a container to see what your gas looks like. Assuming you don't have a water/fuel separating filter?

Edit: missed that the tank was already drained.

Definitely all the symptoms of running lean....

Will try the jerry can idea.

I haven't had a water separator for the five years that I've owned it, thinking I should buy one now though.

 

[Scott06]

3.0 has a water separator in the bottom of the fuel pump remove the bowl of he fuel pump there will be an replaceable element in there .

 

[ronaldreagan]

Anyone want to point me in the direction of a quality mercruiser double barrel carburetor rebuild kit?....

Purchased on off of Amazon and it seems like something that's going to get me stuck on the water.

My accelerator pump is very tight and the new one appears to be small.

 

[Kubaat3lover]

OEM, Walkers, Quadrajet but avoid Mikes Carb !!

 

[Scott Danforth]

Get a mercruiser or quicksilver kit

 

[Scott06]

OEM, Walkers, Quadrajet but avoid Mikes Carb !!

Disagree with the comments on Mikes carb have had very good parts and service from them over the years on three different carbs. Got a very good kit for my mercarb from them

 

[Kubaat3lover]

No instructions how to adjust brass float, because of lack of information and wrong one Ive scratched my brass float tab... No refund, no feedback etc.

And the kit quality... gaskets are like the same from the Chinese kits,
the T stud is different size than the oem, on the picture upper is OEM, lower Mikes carb..
BIG NO!!

 

[Scott06]

No instructions how to adjust brass float, because of lack of information and wrong one Ive scratched my brass float tab... No refund, no feedback etc.

And the kit quality... gaskets are like the same from the Chinese kits,
the T stud is different size than the oem, on the picture upper is OEM, lower Mikes carb..
BIG NO!!
View attachment 328805

not trying to be rude, I saw your comments on the brass float and tried to answer one of your questions, but didn’t seem like you had much experience with carbs based on the questions you asked
I had no issue making the brass float work in my mercarb, not sure how you could have damaged it Unless you beat the crap out of it installing it.

 

[Kubaat3lover]

Sorry for offtopic but dont be rude.. no reason
, I just wanted to ask You abouy the float level...
On their manual is said to bend the FLOAT ARM... but it doesnt work after contacting them he said to bend the float TAB ... thats 2 different things! And I have scrached the tab....

 

[Scott06]

Back to the OP, completely disassemble the carb, clean all the passages, makes sure the fuel filter in the bottom of the fuel pump is clean or replaced, verify clean fuel supply to carb , check fuel pressure/adequate supply . I would think having verified timing the above would take care of itb

 

[ronaldreagan]

OEM, Walkers, Quadrajet but avoid Mikes Carb !!

Ordered a walker kit.... Thanks.

 

[ronaldreagan]

Back to the OP, completely disassemble the carb, clean all the passages, makes sure the fuel filter in the bottom of the fuel pump is clean or replaced, verify clean fuel supply to carb , check fuel pressure/adequate supply . I would think having verified timing the above would take care of itb

It makes sense and other's thought timing would have fixed it too.... but tested the engine in the water by making slight timing amusements all around the spec, although there was some improvement, it didn't fix the problem. Then over time it still progressively got worse.

I replaced the fuel filter, it was very tricky to get it reassembled. Having this concern, I also tried removing the filter at the bottom of the pump and replaced it with an in line filter instead. This didn't help so I put back the stock filtration set up.

When disassembling the carb, I noticed the accelerator pump plunger seems swollen, does not travel smoothly, and will not reach to the bottom of the cylinder without a lot of finagling. The new one from the "no name" kit seems excessively small or loose in the pump cylinder. Let's see what the Walker kit looks like.

The boat is 15 years old and the carburetor was never rebuilt, hoping this will resolve the issue.