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95 Sunsetter Fuel filter question (or maybe something else)


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I have a 95 Sunsetter with the base carbureted Merc engine. Boat has about 790 hours on it.

When I stored it last winter it was running fine. I had had the carb rebuilt in the middle of the

year, but ran it quite a bit after that with no problem. I put it in the water yesterday, and that's

where my story starts:

1. Gas tank had about 8 gallons of gas in it when it was stored and it had been Sta-bil'd.

I put 30 gallons of fresh fuel in it from a gas station that pumps a lot of gas.

2. I launched the boat and it ran fine. I ran it at about 2000 RPM for about half a mile to a no-wake

channel that I idled through for about 10 minutes.

3. After clearing the no-wake area I ran it up to about 2500 RPM and it seemed to run fine. I then pushed

the throttle forward to full throttle, and at about 3000 RPM it started to very noticeably surge and would not

go over about 3000 RPM.

4. I brought it back to my lift. Even though the water separating fuel filter had been changed when the carb was rebuilt,

I went to my dealer and got a new one and spum it on.

5. I took the boat out again and it seemed to actually run worse. It started surging right above idle.

6. After perusing the forums here I thought that there must be another in-line fuel filter somewhere.

I have traced the fuel line all the way from the tank to the water separating filter and don't see one.

Sorry for the long explanation, but this brings me to my questions.

7. Is there another fuel filter somewhere that I can't find??

8. Does anyone have any other thoughts as to the source of my gremlin?

Thanks!!

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A couple other pieces of information.

1. I was told to check the clear tube going from the fuel pump to the carb to make sure it didn't have gas in it (indicating a bad fuel pump). It doesn't.

2. I was also told that there should be a screen where the gas line goes into the carb. I pulled the line off and there is no screen. I also pulled the gas line off where it goesinto the water separating

Filter and thereis no screen there either.

Since it seems to be worse when it is warmer, does it sound like it could be a coil?

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Last Fall, was the treated gas run through the carbs with the engine running? My 350 EFI has IAC, Map, and TPS sensors. Does your carb engine?

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Jweloc,

Thanks for the response. I live about 15 minutes by boat from the launch. I always put sta-bil in and then drive it to the launch to make sure that it is mixed in well.

I'm pretty sure that I don't have the sensors you have with your EFI.

Do you have an in-line filter between your gas tank and the water separating spin on filter?

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No, I only have the water separating filter. Sounds like your jets are gummed up...runs well at low rpm, but when you open it up, the fuel is being restricted.

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Jweloc,

That may be the issue, although I'm having problem rationalizing that since I just had the carb rebuilt. On the other hand, it is a boat so trying to apply rational thought is probably not the right thing to do!

Thanks!!

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  • 2 weeks later...

With a carb, sputtering as you get up to RPM could be a weak fuel pump, yes, that is one thing. It may be something as simple as a piece of sediment that got into the bowls. Could be ignition also. The more the RPM goes up, the more demand on the ignition. Maybe a crack in the cap. Ignition coil tower also.

In the old days of carbs, if a piece of sedement got into the the carb and decided to lodge itself into the primary or secondary jets, at the track, we use to rev the engine and when the RPM's are up, slap the choke closed for a second or two to try and suck it through. A crack in the coil or cap can be found by a light spray of water on it with the engine running. Obviously if it sputters, you have somehting. Check the rotor as well when the cap is off. Usually can see if there has been arcing there.

Check the fuel pump pressure also. If you had the ignition wires off of the engine, make sure 5 and 6 are in the correct order. A small block will run fine until you put a load on it. 18436572.

I'm a little late offering any help but thought I woul chime in since I also have a '95.

Edited by Sunsetter95
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jweloc and sunsetter95,

Thanks for the input. I think the problemis in the carburetor. I was just gone on vacation for a week butq I pulled the carb off and had the guy that rebuilt it take a look at it while I was gone. The results have been somewhat mixed.

1. The good news is that the high speed problem is now gone. It pulls strong all the way up to 4200 RPM (which is all it has ever turned).

2. The bad news is that it doesn't want to idle. When I set the idle to about 700 RPM in neutral it goes up to 1000 RPM and then

back down to 700 RPM continuously. It also drips fuel from one of the primary venturi boosters rather than pulling all of the fuel needed from just the idle circuit. I also notice that the left idle mixture screw has no effect on its idling whether it is screwed all the way in until it seats or is backed all the way out (5 plus turns). The right idle screw works as you would expect it to, running rougher as it is screwed in from 1 1/2 turns out.

3. Based on this, I have concluded that something is plugging up the left idle circuit causing it to not feed fuel at idle. I have therefore pulled it back off and returned it to the carb guy to check the idle circuit.

I'll let you know the results when I get it back. (did I mention I'm a fan of fuel injection?)

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Buster, sounds like the high speed jets are cleaned up. I had the same idle issues this spring. Idle Up and Down,especially when hot and it drove me nuts. After researching, I changed the IAC with no effect , then both the Map and TPS and it corrected the problem. Not sure which one did the trick, but I Bought both at Autozone for a 1995 GM 350 and saved time and money. Your carb doesn't have these huh?

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jweloc,

Those are all highly sophisticated sensors utilized by fuel injection. The carburetor is more akin to creating noise by blowing across the top of a beer bottle.

I hope the cleaning will fix it.

Thanks.

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Buster, sounds like the high speed jets are cleaned up. I had the same idle issues this spring. Idle Up and Down,especially when hot and it drove me nuts. After researching, I changed the IAC with no effect , then both the Map and TPS and it corrected the problem. Not sure which one did the trick, but I Bought both at Autozone for a 1995 GM 350 and saved time and money. Your carb doesn't have these huh?

Can you tell me about how much these cost jweloc? Did you tell Autozone it was a 95 Chevy and they were able to find the right ones?

I may want to do the same thing.

Steve B.

(thanks)

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Steve, the IAC I got from mercuryparts-direct.com for $80.93. The part fit, but I had to rotate the mount(used the old screws, not the new) to fit the electric plug. I took off both Map and TPS and searched the web(Autozone) the same year, V8, etc. I looked very closely at the pictures and determined they matched. The TPS($34.99, #TPS112) was exact. The new MAP($49.99, #SU105) was exact, but I needed to add the tiny rubber sleeve (on the male) from the old MAP to go into the throttle body.

Hope this helps, Jim

Edited by jweloc
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Steve, the IAC I got from mercuryparts-direct.com for $80.93. The part fit, but I had to rotate the mount(used the old screws, not the new) to fit the electric plug. I took off both Map and TPS and searched the web(Autozone) the same year, V8, etc. I looked very closely at the pictures and determined they matched. The TPS($34.99, #TPS112) was exact. The new MAP($49.99, #SU105) was exact, but I needed to add the tiny rubber sleeve (on the male) from the old MAP to go into the throttle body.

Hope this helps, Jim

That does help, thanks much Jim !

Steve B.

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  • 3 weeks later...

Got the carburetor back for the second time about a week ago. Have had it out a few times and now it seems to work fine. I can npw boat instead of playing mechanic.

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