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Boat runing a little rich

S

Steve Diomin

Contributing Member
I have a 1998 Crownline 202br with a 5.0l Mercruiser 305 with thunderbolt 5 ignition with 250hrs on it. It seems to be running a bit rich as you can smelll the fuel burning and it also leaves some black soot on the transom.
I realize that some of this is normal however I think my boat may be running a bit too rich and was hoping to make some adjustments.
When starting cold it used to fire right up, but when starting warm it would crank maybe 10 times then fire up. THis has actually changed this year a bit as it seems to take a while to start cold now also. It seems as the engine is somewhat always flooded. When I start it I dont pump the throttle or anything I just turn the key. Once started the engine runs fine, its just starting and the richness while running i'm concerned about.

I had a guy that knows what hes doing look at it last year for something else, and when we had the spark plugs out I remember him comenting on how much fuel was shooting out of the spark plug holes.....Is this normal??...or does the carb need adjusting??


This past weekend I took the spark plugs out and 6 of them were very sooty and wet. 2 of them were taned/brownish and dry I changed them all and also put on a new distributor cap and rotor. Before I start it back up I was wondering for some further advise on anything further to do or any adjustments I should or could do to the carb.

Thanks
 
Electric fuel pump ? Should be. Check what psi it's giving you first. 4-6 psi 7 is ok no more and certainly not less then 4.

If say the fuel pump is good then i would look to the carb, maybe the float ain;t floating no more. Got gas in it. Maybe seat is bad or dirt is not letting the needle seat good.

Get a kit take it apart remove all rubber off it and let it soak in berrymans. Blow dry, with a can of carb cleaner blow thru every hole and channel, blow dry and then it's time to rebuild it.

When it's time to install the adjustment screw make sure your gentle. DO NOT BEND THE TIP.


 
how do i and where should I test for psi of the fuel pump?.....
is that psi reading for when the boat is running? should i test under running conditions?
 
just plug a gauge it in after the pump crank the motor 3-4 times or till the gauge stops moving. Electric pump will pump the same the second it starts till it stops.

Steve your making me nervous, this is fuel and dangerous, the question leads me to believe maybe you should leave it to a pro. It's your call.
 
Steve Diomin said:
assuming my fuel pressure is high, should I be replacing the pump or is there a way to cut it back at the carb?
Click to expand...


if the carb float bowl is not floating or the needle/seat assy is worn dirty you will have these problems ..I would rebuild the carb.

all that unburned fuel and the carbon generated is wearing out your engine....
 
Listen do you have a electric or manual fuel pump. Manaul will have a yellow hose to the fuel pump as well as a metal line.

The yellow hose is for the fuel pump if the rubber goes inside will send the flow to the carb. If you have fuel in that hose the pump is bad.

Before you do anything reply what pump you have and what was the psi it giving.

Also there is a danger with rebuilding any carb, there is a 50 / 50 chance it can't be rebuilt even by a expert.

Lost art really rebuilding carbs.
 
I beleive it to be an electric fuel pump. All i see coming from the fuel filter/seperator is a black rubber hose that goes towards the tank. It is a 1998. CAn the fuel pump be giving to much fuel?...........i would of figured if the fuel pump ever went bad it was becuase it wasnt giving enough fuel this is way I was leaning towards some issues in the carb, as the motor seems to be getting plenty of fuel.
 
Ok i confirmed myself by going to a website and looking up your motor and yes you have a electric fuel pump for sure no doubt.

Yes the pump can go by giving to mush fuel psi to the carb. No usual but can happen.

So before you take the carb off check the psi the pump is giving you. If you don;t want to that your business.

I already posted whats what with the carb.
 
rebuilding the carb with the basic kit is a job for a boat repair shop.

auto mechanics are not up on these , like 20yrs ago. most likely it is just debris interfering with the float / needle/ seat assy..

since this carb does allow the engine to run , it should not be major repair.. It is possible if water sat in the bowl all winter you may need a new carb ..

taking just the top off , of the carb to inspect the float bowl/needle valve/seat is not that difficult..
 
Im thinking i have to get a carb re-build for sure. After putting in a new cap and rotor and new plugs, i ran the boat for a bout 10 mins and pulled one of the plugs and it is dry but seems very dark/black. Not nice and tanned. First i will try running some carb cleaner threw the tank and see if that helps.
 
so i think hopefully i have some more helpful info that is going to put me on the right track..........maybe you saw , i have another thread going in regards to that i was needing some info on the importance and the what should the purple/yellow wire do and where should it be connected as my slenoid starter in which in my case this wire is just haning there........Seeing this wire is not conected could this have to do with the fact that the boat is running a little rich???>.....as i se this wire ties into the electric choke on the carb.......maybe the electric choke is working properly etc....
 
Steve Diomin said:
so i think hopefully i have some more helpful info that is going to put me on the right track..........maybe you saw , i have another thread going in regards to that i was needing some info on the importance and the what should the purple/yellow wire do and where should it be connected as my slenoid starter in which in my case this wire is just haning there........Seeing this wire is not conected could this have to do with the fact that the boat is running a little rich???>.....as i se this wire ties into the electric choke on the carb.......maybe the electric choke is working properly etc....
Click to expand...

when the engine is cold the choke plate must be closed....
when hot the choke must be open...the choke uses 12volts to it when the ignition is on..check with key to run position you have 12volts to the choke connection ....
 
so if i check for 12volts at the choke (purple/yellow) wire when it is hot it wil not show 12 volts?

On a whole note, what is the best way to start the boat cold. it is a 1998 crownline 5.0l merc carb thunderbolt v. Do i just start from neutral, do i engage the throttle some, alot, do i pump at all..........whats is the best way as it still seems to take a while to start cold. Hot it fires right up. Cold can be 15-20 cranks and it still appears to have that richness to it and floodedness to it once it finally turnsover.
 
Steve
To start a carbed cold engine, pump the throttle lever a couple times and bring it back to neutral. a proper working choke will load up and the start up should be relatively flawless.
If you have an electric choke, there should be 12v to the terminal while the engine is running or the ignition switch is in the "on" position. If not you have a problem with voltage getting to the choke coils within the bakelite cover.
When the choke plate is working properly it will be almost closed when cold, and open,(vertical), when warmed up. If it partially closed after warm up it needs adjusting or repair.
Bert
 
so it is best to always pump the throttle a couple times??..,.... so it doesnt matter if it is electric fuel pump or mechanical?........mine is electric and i thought when the key was in the on position (not cranking) but just on, that signalled the fuel pump to send fuel. Is pumping the throttle the same as this or different?
 
Steve
Pumping the throttle does three things on a carbed engine, it squirts raw fuel into the intake area of the carb, and it also sets the choke plate into position as well as sets your high speed idle into position. The fuel pump is only feeding the fuel to the carburetor float bowl. From there the internal jets and various shafts and lever control,the fuel flow into the engine as it is demanded.
Bert
 
This is how i run a carbed motor. Cold i pump the throttle 2-3 times leave the throttle down 1/3 of the way and crank it. It starts i leave the throttle alone should run at about 1000-1500 rpm. Choke opens you hear the motor change, put the throttle in neutral for another minute or 2.

Then i slowly give throttle till i'm at say 3000-3500 rpm i run 2/3 wot.

I want to stop i slowly back off the throttle till i come to a stop put throttle in neutral and allow the motor to run at least 4-5 minutes at idle.

Shut off motor. Say i want to start after 30 minutes i try it in neutral no pumping nothing, crank it should start.

No start then a pump or 2 and back into neutral and crank no start then it's 1/3 down the thottle as a cold start.

Why i just write all this cause the idle at warm up and idle before shut down
 
Steve Diomin said:
so if i check for 12volts at the choke (purple/yellow) wire when it is hot it will not show 12 volts?

.
Click to expand...

when the ignition swich is on you WILL have 12 VOLTS at the choke / always..hot cold not a factor..

chokes over time fail or are not adjusted properly ...most likely they act up because of paint or corrosion / dirt..
 
so when pumping the throttle before starting, is this pumping actiion in neutral or is this pumping action like engaged the same way you would give the boat throtle in gear?

Which is best
 
Steve Diomin said:
so when pumping the throttle before starting, is this pumping actiion in neutral or is this pumping action like engaged the same way you would give the boat throtle in gear?

Which is best
Click to expand...

there is no reason to put the engine in gear with the priming of the engine with the throttle . this has no effect.. just set it up so the throttle is working not the shift cable ..
 
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