Need help with I/O, please!

[playcat]

Folks, I need help with my sick boat! I am clueless about engines, and two "mechanics" have worked on it and fixed nothing. Looks like I need to fix it myself. its dot a Volvo Pents I/O 5.0 230 horsepower with a 4 barrel Holley carb on top.

Last spring it was flooding like crazy, so I let the marina shop rebuild the carb. After $600 and three towings back to the dock, it seemed to run okay. I hauled it out for the winter and I let them winterize it (I know, I know...).

Now it won't start, unless the choke plate is held shut and cranking like crazy. It won't run at idle, stalling out at 1,000rpm before reaching neutral.

I changed the fuel filter (clean), has good spark. I don't know where to start, or what to look at first. Gas is fresh non-ehanol gas with Sta-Bil added last winter.

I sure could use some help!

[pond tuuunes]

Can you check fuel pressure? Is there a water seperator? But I am honestly thinking fuel pump, JT

[TSip85]

I won't claim to know a whole hell of a lot about motors, but it sounds like a fuel pump issue to me also. Recently my Fairlane did the same thing. It fired up and died as soon as I pulled out of the garage. I figured I just didn't let her warm up before pulling out, then when it wouldn't start I thought I had just flooded it. Turned out I had a fuse out and the pump wasn't getting power. Had just enough gas in the carb to fire, then that was it.

[lakerunner]

A friend had a old OMC Cobra and it had worn linkage and would let it run or idle right

[badmoonrising]

Yep.Check fuel pressure first. No fuel pressure = restriction or bad pump. Fuel pressure good= bad carb. Don't trust carb re- builds. Not a lot of younger guys know carbs anymore. I send mine to flying fish marine carburetors. Never had an issue with them.

Also, check the ink tank pickup screen (if it has one) a common cause of fuel pressure issues if the pump is good.

[Bryden24shp]

The older Holley carbs have a power valve on them, that diaphram blows inside the power valve very easily with the smallest of backfire. I would look at that, too. Good Holley carb rebuilders are hard to find, anymore. I'ld rather rebuild a ThermoQuad or QuadroJet before I would a Holley. Power valve! Make sure they pull the diaphram and check it.

[Bamaman]

There is so much work on an inboard outboard power plant that can be done by a first class independent auto technician. And problem diagnosis is often just like automobiles on engine issues--at least like on older auto engines.

In my area, we can get quality engine work done for $40 per hour vs. $100 for a marine mechanic.

And there are still many, many mechanics of all ages that perfectly understand carbs and their rebuilding. The best mechanics still drag race and run circle track cars, and Holley carbs. are the standard of the industry. If I owned a shop, I wouldn't hire a mechanic that couldn't service carbs.

I would suggest finding someone to disassemble the carb, clean it and reassemble it. Rebuilding is really a very, very simple job, especially since marine carb's often have little of the pollution control items required on automobiles.

And when the carb is rebuilt, put it back on the boat, clamp on the water muff, warm it up and adjust the carb--just like you would on an automobile. There's no difference.

The new 90/10 gas is just a killer on carbs and fuel injections, especially if there are any rubber parts in the fuel system.

[tuned]

+1 on the fuel starved.
A quick and dirty check is to go through your startup/idling problems. Then pull the flame restrictor and take a whiff of the carb. With that much choking and not much firing, you should smell strong raw gas. If you only get a faint hint of gas, you are starved somewhere.
Carb definitely sounds suspicious to me. I would consider sending it to a real pro. Then if you find out that carb is the issue, raise holy h*ll with your original 'rebuilder' and get some cash back.
Sorry to hear of your woes. Good luck.

[ron993]

Yep.Check fuel pressure first. No fuel pressure = restriction or bad pump. Fuel pressure good= bad carb. Don't trust carb re- builds. Not a lot of younger guys know carbs anymore. I send mine to flying fish marine carburetors. Never had an issue with them.

Also, check the ink tank pickup screen (if it has one) a common cause of fuel pressure issues if the pump is good.

My dad has a '63 Ford Falcon that the carb needed rebuilding on. I called my mechanic to see if he would do it, and he told me to call summit racing and order a new one. He said there isn't much of a price difference between rebuilding and replacing, unless it was an original carb.

[cwag911]

Just my $.02 but it could also be a vacumn leak if you have to hold the choke closed. This from an OLD carb guy.

[playcat]

Thanks, everyone! I was thinking fuel pump as well. Its a mechanical pump, and I have never replaced one. How does it go back on with the pushrod? does it go on a certain way?
Told y'all I know nothing about engines...

[badmoonrising]

The pump has a lever on it that rides on the camshaft. Undo fuel lines, remove 2 bolts, make sure gasket is cleaned off. Doesn't go back in any particular way. Start er up and

[playcat]

Thanks again, Ed. I appreciate everyone's help. As soon as TS Andrea blows thru I will get right on it.