Really poor engine performance

This weekend I had 6 people on the boat, I couldn't get past 10mph...I took out the carb filter, it was clean, so tonite I will check the anti siphon and fuel tank filter. If this shows nothing I will expect it to be the carburator and think about a re-buld. The boat has 114 hours on it and it has has at least 1 other tuneup.
 
I think others have mentioned it sound like a fuel problem. An easy way to check is to temporary feed from an auxiliary tank to see what happens? Like a small outboard tank?
 
I'd stop throwing money at it. I certainly wouldn't take apart the carb yet if you're reaching 3500RPM. I wouldn't run it above 4400RPM for long time even if I suspected nothing was wrong. What was your WOT last year? Did you take notice? Are you at a full-service marina? Paying an hour for someone to test it with you may be a good investment.
 
quote:
Originally posted by pstew96

The boat has 114 hours on it and it has has at least 1 other tuneup.

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What did it consist of and how long ago was it done? It isn't all about the number of hours on the engine. If that were true, you could go 10 years between oil changes.

Spark plugs load up, distributor cap and rotor contacts corrode and plug wires dry out and develop micro cracks that cause arcing. Just saying that if the basic electrical and fuel system tune-up stuff hasn't been addressed in a long time, you don't have a good starting point for troubleshooting.

Getting it running right will be a hit or miss proposition. Unless you get lucky it'll get expensive fast.
 
So, tonite I checked the anti siphon valve, looked really clean, the running temp is about 175deg. Last year she ran nicely. If I can get a gasoline can I might try the by pass the tank test. Its raining, otherwise I would have taken the carb out.
 
Looking and cleaning INSIDE the Dist Cap and Rotor could be good about now. Conductive "dust" could have built up in there and can make it miss. Pay attention to center terminals. Scrape flakes from the 8 plug wire contacts. Spray clean with carb or brake parts cleaner. VENTILATE before starting.

A cracked cap or rotor is hard to see till it's really built up a carbon trace. A fine one looks like a pencil line.

Other than that, if you can run it in the DARK, you may see spark jumping where it shouldn't be. You shouldn't see any.
 
quote:
Originally posted by pstew96

Its a 2004 Maxum 2400 se, its got a 5.0 merc and Alpha drive.. only 110 hours on it.

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if the hours are this low, it is possible that you have some "stuff" at the bottom of the fuel tank that may be getting hung up on the fuel pick up. running on a spare can of gas as you plan will validate this.
 
most often when this happens its 2 plug wires mixed up from winterizing shes running on 6 not 8
 
Ok, so I checked the distributor and it was a little green with corrosion, so I changed the cap and rotor, then I checked the PSI on the fuel pump and it read about 9 PSI, then I blew air into the tank but forgot, the anti siphon prevented that so I sucked and got gas. I have yet to check the spark plugs and if they are good I will expect its the carburator. The boat runs better with two people and I got to 27 mph where with 6 people I couldn't get past 10 mph, when I go WOT it pops alot like mini back fires. Thanks all for your helpful input!
 
Have you checked that the plug wires go to the proper plugs?
 
Check the compression on the cylinders. I had same issues and it turned out to be a "tuliped" valve.
 
I'm going to check the timing Thursday and I'm draining the gas tank by using the boat gently. See if that helps.. Still top speed is about 25 and RPMs as high as 3600.
 
Can you confirm that

1. the spark plug wires are seated on their spark plugs/terminals on both ends and

2. the plugs/terminals are the correct ones?

Order is 1-8-4-3-6-5-7-2

Be particularly careful of 5 and 7. They are close to each other

1. side-by-side on the distributor

2. side-by-side on the spark plugs

3. sequential in the firing order
 
Yes, no one has had any access to the boat, it was in a warehouse over winter. Timing sounds about right, I have to get a light and check the manual, don't know what the reading is supposed to be yet.
 
So I checked the timing and it is only 1 or 2 degrees off, I expect not enough to make a difference. I ran the gas tank dry, will fill it new. I dropped the flame arrestor nut into the carb but was able to get it out, I wonder what would have happened if I didn't..?? I'm thinking I will take the fuel line up from the tank and see if its crudded up today. My friend told me I could turn my carb to an EFI, I'm going to look into that.
 
There is nothing wrong with carbs as long as they're working ok. I have fuel injection and that brings in different and more expensive problems. Why not do plugs and wires since you did the cap and rotor. Also is 9 psi the correct fuel pressure? Since you ran the tank down put fresh gas in and see if your problem is still there. What size prop? Is it the original size? Also your engine should run in the 4400-4800 rpm range and should run a prop that puts it as close to the 4800 rpm as possible.
Rob
 
If you feel a carb rebuild is warranted I suggest you send it to Tredwell Carb in NY. That is if you are in the northeast.

There is a lot more to rebuilding a carb than throwing in a rebuild kit.
 
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