Lots of bogging before 3000rpm - Please help!

[itchyfishnv]

I purchased a new carb from http://flyingfishcarburetors.com/ (mercarb sn: 1389-9350) for my 87 Stingray, 3.0l as its been about 10 years since I've had it rebuilt. Up until then the boat ran great. While waiting for the carb to come in I replaced the thermostat. New carb comes in, put it on, starts up fine. The only adjustment I had to make was backing out the idle mixture screw about 3/4 of a turn to make it idle. It ran great until I took it on the water and it overheated. Turns out I had a piece of the spring from the radiator hose caught in the water circulation pump and also some pieces of impeller through out the cooling system- I have no IDEA how long they've been in there because I haven't blown apart an impeller in at least 8 years as I replace it every season. So i said it's been a while since I did anything w/ the cooling system. So I got a new impeller pump (impeller, base, housing), circulation pump, manifold and riser. I piece everything back together and it idles a little rough, so I thought okay maybe the timing is off, timing is at 6 degrees BTDC. I then take it out on the water to test it and now it seems like whenever I am anywhere from 1200-3000 rpm its really boggy and drops in RPM for a second, anything above 3000 rpm on plane and it runs like a top. Also, once warmed up it wont stay idling. I really dont know where else to go from here. On a side note, I replaced all the fuel filters, new gas, points, plugs, ignition wires. Plugs are gapped to spec and point gap is at 20. dwell at 30.

PS - The manifold I received was a 6 bolt Barr, the one on there was a 5 bolt mercruiser (original as of 95, anyway). The ports looked identical.

Thanks in advance and sorry for long message, I wanted to be sure I included all the sequence of events and parts replaced.

-Nick

 

[Scott Danforth]

sounds like a carb issue. from your description, it could be running lean

what was wrong with your old carb?

new doesn't equal good

also, since your overheat, have you done a compression check?

 

[ThomW]

I'd tend to agree with Scott.. Seems like a carb issue. From the sounds of it, it seems like the pilot jet could be clogged, not adjusted right. Did you check float on new carb to see if its set at correct level?

 

[itchyfishnv]

sounds like a carb issue. from your description, it could be running lean

what was wrong with your old carb?

new doesn't equal good

also, since your overheat, have you done a compression check?

I was told that the accelerator pump was gone, I wasn't able to get to plane at all with out it feeling it it was dying. I had the fuel pump checked as well and it is pumping out fuel as it should be. I did a compression test on all 4 cylinder and none were below 110. I also performed a leak down test after, there was only moderate leak down.

 

[itchyfishnv]

I'd tend to agree with Scott.. Seems like a carb issue. From the sounds of it, it seems like the pilot jet could be clogged, not adjusted right. Did you check float on new carb to see if its set at correct level?

I did not check the float, honestly- I know nothing about carbs which was why I was skeptical of rebuilding it myself. Do we have any how-to's on how to check?

 

[ThomW]

http://forums.iboats.com/forum/engi...-how-to-measure-float-drop-level-mercarb-2bbl

Here is at least one post/forum on checking a 3.0's carb float. Just to clarify, the new carb worked well, until the boat overheated? How long did you get to run it before it overheated? The fact that it worked well before overheat makes me question my previous post on the float. That would be more applicable if it never ran quite right. It could also be an issue with the choke plate, if it won't idle after it warms up.

Just to make sure, when you put new carb on, did you make sure you put on the gasket(s) and that they were the correct gasket and or lined up right?

Does the carb spray gas when you pump the throttle? Just want to verify you are not having some sort of vapor lock issue with the gas tank/lines.

 

[Scott Danforth]

I would have gotten a $5 accelerator pump kit (or a complete $30 carb kit) and rebuilt your old carb vs buying a new one.

reading post 1, its unclear if the boat ran well for a long time before your overheat, or it ran well at idle and you went to over heat. in short, how much time do you have on the new carb? hours or minutes?

110psi is low. what were all 4 numbers? they should all be within 10psi of each other and all about 150psi

 

[itchyfishnv]

http://forums.iboats.com/forum/engi...-how-to-measure-float-drop-level-mercarb-2bbl

Here is at least one post/forum on checking a 3.0's carb float. Just to clarify, the new carb worked well, until the boat overheated? How long did you get to run it before it overheated? The fact that it worked well before overheat makes me question my previous post on the float. That would be more applicable if it never ran quite right. It could also be an issue with the choke plate, if it won't idle after it warms up.

Just to make sure, when you put new carb on, did you make sure you put on the gasket(s) and that they were the correct gasket and or lined up right?

Does the carb spray gas when you pump the throttle? Just want to verify you are not having some sort of vapor lock issue with the gas tank/lines.

yes the new carb seemed to work fine after it overheated, but again it only ran for about 10 mins before I noticed the temp above 200. Yes they provided the gasket and was aligned properly, i made sure that the plates didn't interfere w/ the gasket.

 

[itchyfishnv]

I would have gotten a $5 accelerator pump kit (or a complete $30 carb kit) and rebuilt your old carb vs buying a new one.

reading post 1, its unclear if the boat ran well for a long time before your overheat, or it ran well at idle and you went to over heat. in short, how much time do you have on the new carb? hours or minutes?

110psi is low. what were all 4 numbers? they should all be within 10psi of each other and all about 150psi

I literally had 10 minutes on the new carb before it overheat. I almost replaced the t-stat housing at the same time I replaced the carb as it the bolt broke off in the lower housing (rusted in there).

Cyl 1: 110
Cyl 2: 120
Cyl 3: 110
Cyl 4: 95

 

[itchyfishnv]

I noticed today after I ran it for a while I was back to square one before I replaced the carb... The boat ran fine for about 15 minutes at all RPM ranges- Still rough idle, but none the less no bogging anywhere. Then I ran it under full load for a mile or 2 and came back to idle, after that the boat ran like complete crap in all RPM ranges, very boggy and sounded like it wanted to die, once in neutral it shut off. But I did notice a popping sound coming from the engine when it was running like crap. I have a feeling I'm in for a new engine or a rag and a match to the gas tank. I never heard the popping before,I've very novice when it comes to engines. Realalistically speaking, how hard is it to drop in a crate? I would need to disconnect the drive completely, engine coupler? I've done an engine swap on an old YJ before and it wasn't all that bad.

Just noticed... I have a lot more than usual oil blowby coming out of the breather on the top of valve cover... this is indicative of worn piston rings, isnt it? Seems like the more blowby the worse it runs. Has to be a compression issue, huh?

 

[Rick Stephens]

Were your compression numbers done with engine warm, the carb open and choke plate open, and you want 5 complete compression cycles on each cylinder? Did you try a few squirts of motor oil into the cylinders as a ring test? Running the compression test dry, then squirting a little oil in and running them wet, tells you if rings are the issue.

Pretty typical to have one or both end holes showing lower than the middle. Engine will run that way, though not as efficiently as it used to. A little puffing out the breather is pretty normal on a 4 cylinder engine even when new, lots of air flow out the breather is sign of worn rings.

Pulling a boat engine is one tenth the job in a boat as a car. Pull the drive (8 nuts and 15 minutes) You disconnect fuel, electrical, water, exhaust and control cables, remove the 2 rear motor mount bolts and the lag bolts on the front mount, pick the motor up and slide forward a little. If you have the tools on hand, 45 minutes. Hardest part is setting up something to reach over the stern ad lift the motor - that is usually higher than many automotive hoists can handle. Hanging a chain hoist off a tree branch or A frame can be easy solution. LOTS of posts on creative engineering a solution in this forum.

And my opinion is you still have either a carburetor problem or a fuel source issue.

 

[itchyfishnv]

No Title

I did do the test w/ the engine warm and the choke was open. I just did another compression test. The results are attached. Not sure wtf is going on here.

 

[Scott Danforth]

the popping when its running rough is the motor running lean. also known as a lean sneeze. when that happens, there is also detonation happening (bad). could be caused from any of the following: crud in the carb, bad carb setup, plugged fuel filter, bad fuel pump, plugged anti-siphon valve, or crud in the tank.

my guess is that when you first start it up, the motor is running partially choked, and when the choke opens, its running a bit lean.

if those truly are your compression numbers with the motor warm and throttle open, its time for a rebuild.

as Rick stated, pulling the motor is not that hard. installing a new one isn't much harder, other than the repetitive insertion and checking the alignment bar

 

[itchyfishnv]

the popping when its running rough is the motor running lean. also known as a lean sneeze. when that happens, there is also detonation happening (bad). could be caused from any of the following: crud in the carb, bad carb setup, plugged fuel filter, bad fuel pump, plugged anti-siphon valve, or crud in the tank.

my guess is that when you first start it up, the motor is running partially choked, and when the choke opens, its running a bit lean.

if those truly are your compression numbers with the motor warm and throttle open, its time for a rebuild.

as Rick stated, pulling the motor is not that hard. installing a new one isn't much harder, other than the repetitive insertion and checking the alignment bar

Yeah but shouldn't the choke fully open when its at normal operating temp? It's def at full operating temp well before it starts running bad. There have been times where I've ran it for hours and then all the sudden it starts running lean. The fuel is good and all the filters are new. What should the PSI be for the fuel pump?

 

[Scott Danforth]

Fuel pump should be between 4 and 7 psi.

 

[itchyfishnv]

Thanks, I'll double check the fuel pump tomorrow at some point. It's just so strange that it will run fine and then all the sudden run so bad after 15-20 minutes. I'm at my the end with this thing, I'm going to have someone from the marina (on the side) look at it. I'll report back my findings, if I don't- it became a sunken treasure. ha.

 

[itchyfishnv]

No Title

Pulled the carb off today and cleaned it. Question though... the gasket that was supplied was just one big oval hole and the one before was 2 holes. I also noticed that the gasket is larger on one side. Why is that? Does it matter which way the gasket goes on?

 

[airdvr1227]

While all this is happening have you contacted the folks at Flying Fish to tell them there may be a problem with the carb? I had a bad experience with them a few years back. Bought a re-built carb in February and didn't install it until May. Long story short the idle circuit was all dorked up but too much time had passed from February. They wouldn't refund my $$.

 

[itchyfishnv]

Yes, I've contacted them via email but have not had a response yet. My plan is to call them today.

 

[itchyfishnv]

I spoke with them today. They are sending me a new carb this week. They said they see this from time to time about 1 in 10, Kind of a lot if you ask me, for a company who's DBA guaranteedcarburetors.com