1993 SN Just Started Running Bad

I have a 1993 Ski Nautique with the 351W Standard PCM motor. It has generally run fine and was working great until a few days ago. The choke doesn't work so you have to pump the throttle a bunch of times to get gas into the carb, but once it warms up, the boat has always worked ok. The other guy I own the boat with took it out on July 4th and it ran great. When he went to start it on July 5th, he had a hard time getting it started and then it idled rough and died a few times. He ended up just putting the boat away. When we went out today, we had a hard time getting it started. We had to pump the throttle more than usual and then it would only start while pumping throttle until it turned over and then holding wide open. The engine would run at about 2200 RPM at wide open and ran really rough. If I dripped a little fuel into the carb as it was running, the engine would rev a little. If I jiggled the accelerator pump to get it to squirt more fuel in, the engine would rev and hold a higher RPM for awhile. At higher RPM, it seemed to run more normal. The engine only wants to run if the throttle is wide open.

I tried changing the spark plugs because they were probably due, but it didn't make any difference. I'm thinking it is a fuel issue, but let me know if you think it's something different. Since I don't have the boat at home with me, does anyone know if these have a fuel filter in the carb, or is the fuel water separator the only fuel filter? It has a Holley Carb and looking at the pictures on the web site, I think it's the 4160 Carb.

Advice anyone?

Starter fluid is pretty harsh on cylinder walls, it washes off the oil coating. Try hooking a small gas can up to the fuel pump for a test, that will eliminate hoses, separator, venting issues, etc without much work.

Seems like we've(these 2 forum members) have had this conversation before about the harsh effects of starter fluid vs raw gas. We'll have to agree to disagree. Playing with raw gas is dangerous to people, which are more important than any supposed damage (they are oiled from under the piston) to the cylinder walls. This is bad advise! Think about it! I saw a guy on fire when I was a kid and went to school with a boy with a fire scarred face. Bad things can happen.
That aside, bypassing the whole fuel delivery system with starter fluid is a better diagnostic test. If it runs fine while spraying starter fluid in the flame arrestor (which also may be clogged by oil mist and dirt, check it out with a strong light), then you know it's not electrical in nature. Fuel, spark, compression and timing is all it takes to run an engine. Check it out in that order. Autozone has a tool lending program for free (with deposit) so you may need a fuel pressure tester, compression tester or timing light as you work through this. Write down your results and take Iphone photos
And keep a fire extinguisher handy and wear safety glasses, gloves and long sleeves. Seriously!

Hey guys, thanks for the responses. I'd kind of rather not have the thread turn into a starter fluid argument thread. I'll consider both sides there and do some research on that elsewhere.

Now, I have a question about that screen where the fuel line enters the carb. Is that just a screen that I could potentially clean out if it's clogged, or is there a filter in there that I should replace? I kind of want to have whatever filters I might need to buy in hand before the next time I drive out to work on my boat. It's stored 45 min from my house.   

It's available here
http://www.skidim.com/prodinfo.asp?number=R024025

You may also want to have a new metal fuel line.
http://www.skidim.com/FUEL-LINE-PCM-302_351-FORD/productinfo/RA085002B/
They are easy to crack and leak when removing them, mine did. Since you have to drive so far to get at it, make sure you have the right wrenches to hold the carb side while turning the fuel line side. with a proper wrench meant for going over metal tubing (the name escapes me at the moment). Yours might already be buggered up from someone using a slip joint pliers or vise grip wrench in the past. The brass fittings are real soft.

I have flare end wrenches from 3/8 up to 5/8 in 1/16 increments. Not sure how big I need. Anyone know? I can't picture how big the two sides are.

Thanks.

Greg,
I suggest some grease or anti seize between the flare nut and the flare but NOT on the sealing surface of the flare. This will allow the steel tubing to slip in the nut when you tighten it. If you don't, a common problem is the steel tubing will wind up clockwise when you tighten the nut. Then, with engine vibration and the steel tubing wanting to move back counterclockwise, it loosens the big flare adapter in the carb.

Carb inlet fitting is 1"

Starting Fluid/Ether - maybe you have not see the results but I have. Pistons broken is most common damage, I have even seen an intake manifold blown right off an engine by poor use of starting fluid. Do I ever use it, Yes, am I very careful when I choose to use it. Yes.   A direct spray into a carb with starting fluid results in one, maybe two pistons getting most of the fluid. This concentration is enough to blow up and cause damage.
If you have two people have one turn the key to get the engine spinning while the second gives a quick shot towards the carb top. Doing it while spinning gets a more even mix into all 8 cylinders and each gets a much smaller amount.   Still dangerous but far less dangerous.   
I keep an old lighter fluid can in my garage with gasoline in it. It puts out a small squirt of gas when needed and is much easier to control than a Gas Can or other container.
Still dangerous if used badly but reduces the amount of danger quite a bit.
The lighter fluid squirt is controllable enough that I can make a 350 Chevy idle fine even when not hooked up to a fuel supply line.   Works good when determining fuel related issues.

As others have already mentioned it sounds like you have lost your fuel supply through the main jets of the carb. Maybe dirt or crud is inside the carb blocking the jets.
The fact it is trying to start with pumping tells me the accelerator pump circuit still has fuel so the bowls must still have fuel in them?   

Red neck ether

Update: Nothing to do with fuel/carburetor. Ran compression check and had no compression in cylinder #8.   Pulled valve cover and one of the rocker arms was so loose against the top of the valve it rattled. Pulled head and found one of the valve seats had separated from the head so exhaust valve was stuck open. Piston hit valve but cylinder wall looks OK and piston is dimpled but doesn't have a hole. Now I need to round up a new head or pair of heads...

GT40P heads are cheaper than standard GT-40 heads, and will serve you well from a power and compression standpoint as well the as plug angle change being nice for maintenance access.   if your engine originally had GT-40's and they are in re-buildable shape, you might get some trade in value from them.

Delta Greg wrote: Will GT-40 and GT40P heads bolt right onto the stock PCM 351W block? I've read mixed info about the spark plugs in the GT40P not fitting with 351W exhaust manifolds and the head bolts in the GT40P needing to be drilled and tapped from 7/16" to 1/2". Do people have any experience swapping these heads into their boat?

Yes,they just need to be drilled not tapped and then the P's bolt right up. Brass core plugs are nice to have too. Sparkplugs have no issues with manifolding on boats only on cars

you can purchase the heads pre-drilled and with the brass plugs.   I am running P's on my boat.   you may need spark plug wires too, since the plug angle is different, but that is only if your wires were pretty tight to begin with.