OMC 5.7 V8 power loss

[shellone]

It must be an 1989 recently rebuilt V8, runs smooth but does not develop full power when requested. Initially, cleaning the valve just at the fuel tank (with the ball and the spring) did the job, maybe some debris got to the fuel filter. Am on a long trip, tried to find a replacement filter to no avail, just could remove and empty the present one from some dirt ... looked like tea leaves, like I had found in the valve. Been cruising slowely through rivers and canals halfway through Europe, now in the open sea I have problems maintaining a decent cruising speed. The spark plugs I have changed, but whenever I find technical support nearby I hear the same 'we have no time'. Does anynody have a suggestion what I might try on my own ? What could cause this engine to not have igs full power ? It either reaches full power but stalls after some miles, or does not reach anywhere close cruising RPMs ...

 

[PITBoat]

Until you eliminate the source of the "tea leaves" or whatever else, you're gonna hafta keep cleaning and emptying periodically...

 

[shellone]

The source is the fuel tank, which I cannot clean while navigating ! But it seems as most of it found its way out of there, because last two times valve and filter where clean. Hope to find a spare filter today, but still wonder where else to look for this bottleneck. Engine does not stall anymore, but if pushed to high rpm runs as if it still does not get enough gas.

 

[Scott Danforth]

you cant re-use the fuel filter, much of that stuff is now in your carb. you will need to tear the carb apart and clean it.

 

[Lou C]

Ultimately the solution to your problem is cleaning out the fuel tank which I'm sure you can find a marina in Europe that will do that. But specifically do you have a proper fuel/water separator? You should be using a better 10 micron cartridge for this, and the best filter really is the Racor with the metal bowl for inboards. Also if it has the original Rochester Quadrajet carb there is a small filter in the inlet where the fuel line connects to the carb. Normally this will be clean if you have a good large cannister fuel/water separator and it is really just a screen on the marine version, the auto versions used a regular paper filter there. But that should be checked as should the main filter.

 

[shellone]

Thank you very much for the useful suggestions. Acctually, no, navugatung thru Europe I have not been able to find anybody to do any useful job on a boat. Coma back in 6 weeka was the friendliest answer. Bought two fuel filters in Cologne and two in Lyon, giving both dealers the serial of the original filter ... when I went to change it, none of the new ones fit. So of course dirt came to the carb a Rochester Quadrajet, but as I can't find no gaskets the buck stops here.

https://youtu.be/UCVijNeSUGU

This was yesterday, lucky the engine drove me through thove waves ... but today nothing goes, but cough and hickup no constructive sounds from the engine department.

​​​​​​Can I disassemble the carb and have a chance to reassemble it, cleaned, with no spares ?

Otherwise the buck stops here, in the port of Sanremo, Italy. Gotta get a 3.5 tons trailer set up and drive the rest of the way. Certainly saving money, but, hell, I had really blued eyed as I am thought I might compete this trip.

It would be helpful if anybode can give me links tp order OMC spares !! Maybe when I get home I have the spares needed to bring this boat back in shape.

 

[Lou C]

OK taking apart a Quadrajet is not really for a beginner because there are a couple of tricks you just have to know, and keep in mind these were used on literally thousands and thousands of Chevrolets, Pontiacs, Oldsmobiles, Buicks and Cadillacs from the mid 60s to the mid 80s, so the people who knew how to work on them are all older now, if they are even still with us. Changing the 2 filters is really a simple job. You need a filter for the carb inlet and the fuel water separator. Post up a pic of your engine so we can see what you have. Your boat handled those waves great, bravo Captain!

Try looking on this site...
http://ww2.iboats.com/Fuel-Filter-18...view_id.187706
this is the fuel inlet filter for the Quadrajet....

http://ww2.iboats.com/Sierra-18-7846...view_id.187572
the large water separating fuel filter

 

[shellone]

Especially for you, Admiral Lou !

Earlier today I decided to travel home on Monday, come back with car and trailer and recover the boat; then, for good measure, I ordered on eBay in the UK a set to eventually repair the carb:

https://www.ebay.it/itm/ROCHESTER-Q...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

later in the day I found a vendor from Venice, who sells a carb that was in use on a 78 Corvette C3

https://www.ebay.it/itm/Carburatore...rentrq:c655466b1740a692452ce62dfffb5de0|iid:1

If you have the patience and can advice as to: Should I buy the used carb from this Corvette and have a decent chance that it will fit the flange on my OMC so I can tow back home a boat that I have seen run properly before taking off the water ?

With a limited set of tools, and time to spare to find whatever necessary, can I replace the 'dirty' carb with this one that was in a running car three months ago, without need of a new gasket ?

If I need a non metric key I can find that easily, if I need a Rochester or OMC gasket I am lost ...

Look forward to hear your opinion !

Thanks !

P.s.: Can I send you a PM and close this post?

 

[Scott Danforth]

do not use an automotive carb in your boat.

there are many things that make a marine carb safe that are not on an automotive carb.

when you have a fuel leak in a marine carb, it leaks internal to the motor making it run like s#!t so you fix it.

when an automotive carburetor leaks fuel, it leaks on the ground and the car moves on.

when an automotive carburetor is installed in a boat and it leaks....... it fills the bilge up with fuel and fuel vapors.

you will blow up

 

[Lou C]

Agreed of course do not use an automotive carb on a marine inboard, for both safety and performance reasons. The problem with replacements is that there have not been new marine Quadrajets since 1990 or so. If you want a new carb to avoid problems your choices are Holley (4175) or Edelbrock (1409).

 

[Lou C]

PS avoid “remanufactured” Quadrajets because they can be combinations of various carbs that don’t work well together.

 

[shellone]

Thank you very much for the advice, will stick with the intention to fix my own carb for now ... memorized the Edelbrock 1409 as an alternative if it will not be successful. Anyway, learned to not use auto carbs even if they have the same name !

Had to buy a new 3.5 ton trailer and a car (used Jeep) that can tow it so for now the problem is settled ....

 

[Scott Danforth]

rebuilding a rochester is not hard just make sure to epoxy in the welsh plugs

the webber that was on various mercuisers is a rochester clone

the edelbrock is a variation of a rochester clone

i personally like holley carbs, however real holleys in the past 10 years have had quality issues. companies like quick fuel or AED make great holley clones, but you can rebuild a holley many times without a problem

the key to rebuilding any carburetor is to clean the parts, and verify every passage is clean. this requires running a fine wire or monofilament fishing line thru ever passage.

 

[Lou C]

Scott I think the Weber on Mercs is actually a Carter clone as is the Edelbrock. Edelbrock did build Quadrajets after GM quit making them for a while but I don't know if any were marine units. The tricks to doing the Quadrajet rebuild (getting the air horn off) are driving the pin that holds the lever for the accel pump back just enough to work it out, not all the way up against the body of the carb so you can slide/pry it back, and disconnecting the choke linkage on the other side. Then when cleaning, the air emulsion tubes (they have brass collars on them) can be hard to clean, takes a lot of soaking and blasting with a real air compressor not canned air. When re-assembling, the tricks are getting the primary metering rods in right, lining up the air horn gasket right and being careful to also line up the secondary metering rods. But all in all, not harder than taking a Holley apart because the gaskets don't get stuck on like those blue Holley gaskets.
PS the welsh plugs on the marine units made after about 1980 or so don't seem to leak as much as the older ones....

 

[shellone]

For a very brief moment, after cleaning the carb, with the boat out of the water, I started the engine and it ran fine (like I had never heard before). Then it began misfiring, more and more frequently. It seemed to be cyl. 2 and 6, then 3 and 4 ... so I realized that the contact in the distributor was totally worn out. Happiness did not last long. Just got the contact (and condenser), hope replacing them will not cause the next illness to show up !

 

[Scott Danforth]

make sure you use a dwell meter to set the points

 

[shellone]

Thanks Scott ! Given the continuing unavailability of qualified technicians, for now I am happy to have replaced the points and the condenser, set to the right 'moment' and registered them with 0,4 mm aperture. Engine started fine, runs smooth and I will soon test it on the water. Funny enough, the idle had been jumping between 400 and 700 lately, now with the clean carb and the new points is dead right on the 600 mark. If I can find a technician to set the ponts right, I will gladly do so. Maybe out of lazyness two people told me it is a job that needs to be done in the water with engine engaged ... I'll take the risk and jump 200 Euro for the crane and test, hoping that one of them will be able to show up at the right moment. Just wanna see this boat gliding fine for once, after 3000 miles since I bought it in disarray.