Fuel Filter
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=2752
Printed Date: November-23-2024 at 7:00am
Topic: Fuel Filter
Posted By: jimbo
Subject: Fuel Filter
Date Posted: November-27-2005 at 5:47pm
Any tips on replacing the long fuel filter on my '84 Ski Nautique? I tried it last summer and gave up.
I took the boat out for a drive on Thansgiving and it surged a little after a while. I thought it was running low on fuel so I idled back home. Filled up with fuel today and took her for a spin. After about 20 minutes at 3200 RPM, she started surging again.
I have an in-line fuel pressure gauge. It read 6 psi but would drop down to nothing after a few minutes at 3/4 throttle. Pull back the throttle and it builds up pressure. If it were a bad fuel pump, it would give low pressure regardless of the rpms, right?
So, any tips on replacing the long filter? There's also a small filter plugged into the fuel line about 10 inches before the carb. I think I'm going to get rid of that one and replace the rubber fuel line with copper. Any comments?
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Replies:
Posted By: 79nautique
Date Posted: November-28-2005 at 8:12am
If you have an electric fuel pump you wouldn't see a change in pressure relative to rpm. But since your's is not and is a manual pump then RPM will effect pressure. Sounds like a fuel pump issue to me but you should change the filter first or also if you replace the pump as well.
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http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique
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Posted By: marks
Date Posted: November-28-2005 at 12:01pm
Jimbo,
My 89 also has the fram long filter. The body of the canister unscrews from the top, similar to an oil filter. There is usually a drain valve on the bottom of the canister. Also, some of them have a hex shape on the bottom that you can put a wrench on.
In changing mine, I have found it is almost impossible to unscrew the canister in place. I pull the fuel lines, and unbolt the whole thing from the mounting bracket (the four bolts on top). I drain as much gas as I can through the valve on the bottom. Then I place the canister upside down in a wood vice, gripping the top. The top is sort of square shapped. I then use a large wrench on the hex head on the botton to unscrew the canister. Some gas will spill out when you open it, so be carefull.
Your new filter should come with a new gasket. Make sure you dig the old gasket out of the top pefore inserting the new one. If its really old, the old gasket may be as hard as a rock.
I hope this helps,
Mark
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Posted By: Bob's2001
Date Posted: November-28-2005 at 3:57pm
I have an 83 and it's definely easier to do like Mark says and pull the whole thing.
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Bob Ed
83 2001
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Posted By: jimbo
Date Posted: November-28-2005 at 4:04pm
Thanks for the advice on changing the filter. It'll probably be Saturday before I have a chance to work on it. I love the Fall weather but don't care too much for the short days.
I don't know much about the fuel pump. Is changing it difficult?
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Posted By: Bob's2001
Date Posted: November-28-2005 at 4:26pm
The fuel pump on a 351 is put on just like on a car or truck. Remove the fuel lines in and out, 2 bolts hold it on. When you install the new one be sure the pump arm is under the plunger in the block. New gasket, 2 bolts and fuel lines connected and your in bidness.
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Bob Ed
83 2001
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Posted By: AWhite70
Date Posted: November-29-2005 at 9:46am
I replaced the Fram unit on my '79 with the spin-on header and filter that SkiDIM sells. It makes filter changes a lot easier and leaks a lot less than the Fram did.
My Fram always smelled like gas and weeped in certain spots no matter how many times I changed gaskets or tightened the thing....good riddens.
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AWhite70
http://www.correctcraftfan.com/diaries/details.asp?ID=562&sort=revyear&pagenum=5&yrstart=1976&yrend=1980" rel="nofollow - '79 Ski Nautique
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Posted By: jimbo
Date Posted: December-04-2005 at 7:48pm
So I changed the Fram filter/water separator. Thanks for the advice; it was pretty easy to remove the complete assmebly. It certainly needed to be changed. Rusty water and chunks of nasty came out with the gas. There was a lot of crud in the bottom. I used the air compressor and carb clear to clean it up.
Now for the bad news. It still has the surging problem. I noticed a couple of other interesting things:
1. The in-line fuel gauge reads 6 psi at idle and for a little while when under way. After a few minutes at 3000 rpms, it suddenly drops to 3psi. About 30 seconds later it suddenly drops to about 1.5 psi. After another 30 seconds it drops to zero. After another 30 secs it starts surging. The readings don't gradually drop; they drop in increments. Odd.
2. It only surges while underway. I haven't been able it get it to drop below 6 psi with it in neutral, even after about five minutes at 4000 rpms or by shifting to neutral when it starts surging and reving back up. Again, odd.
3. I replaced the fuel line from the tank to the water separator a while back. Against my better judgement, I used Autozone fuel line rather than marine fuel line. Could the thinner-walled fuel line be sucking in on itself and causing these problems? Thats a pretty long run from the tank to the filter.
Any any comments before I order the fuel pump? It just seems to me if the pump were bad, it would have low pressure at idle as well.
Thanks again.
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Posted By: 79nautique
Date Posted: December-05-2005 at 7:56am
Let me repeat myself FUEL PUMP replace it.
Because the pump moves at a slower speed at idle the pump can keep up but as the rpm increases it cannot so you can do one of two things, keep chasing your tail or replace the fuel pump, your choice, not trying to be mean or anything.
The automotive fuel line is ok, I wouldn't have selected it, but it's not going to effect anything. Also now that you have the filter replaced you need to change it regularly maybe once a season to play it save, cheap insurance so to say. The rust and other junk in the filter needs to be looked at a little closer and make sure that you do not have a gas tank rusting out on you which will lead to other issues down the line. I would say run it for a while, say a couple of days on the water and check the filter and make sure there isn't junk in it a gain if there is then you are going to need to replace the gas tank or I think there is some products out that you can line it with and not have to replace it. Another option is to try and look into the tank and see if there is any signs of rust. Some tanks are aluminum and others are steel, which I'm guessing is in your boat, and then there are aftermarket plastic tanks as well. If you have an aluminum tank then don't worry about it and the rust and junk in the seperator is just from old age.
The fuel pump is easy to change just make sure that the arm of the fuel pump engauges the eccentric. Just tip the arm down towards the oil pan as you insert it into the opening and you cann't miss. You should feel and see a small gap and tension has the mounting faces come together. Hope this helps out and by all means get a marine grade fuel pump and not an automotive, I know it cost a little more but it's a safty issue.
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http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique
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Posted By: jimbo
Date Posted: December-05-2005 at 9:20pm
Ok I ordered a new fuel pump and some other odds and ends. And yes, it was the marine type. I may try to get buy with some automotive fixes in a pinch but fuel pump, alternator, starter, dizzy -- all marine grade baby!
I guess I still don't understand how the pump works -- I figured when the engine turns faster, the mechanical pump would pump faster and cancel out the increased fuel use. Maybe when I replace it I'll understand it better. Plus I'm just a tight a$$ thinking a 23 year old fuel pump should still have some life left in it.
Thanks for the tip on checking the fuel tank. I think it's ok. I relaced the sending unit a couple of months ago and I don't remember having any reason to think it wasn't aluminum. I guess the easiest way to check is to see if a magnet will stick to it.
I'm reasonably sure the rust and gunk was because the filter hadn't been changed in years -- if ever. That was evident by the brittle fuel line. I've owned it a year and a half and I've found a lot that's been neglected.
That's a good idea to check the filter after some use. I'll run this tank down pretty low then pull the can again and see what it looks like. I was wanting to repaint the can and head anyway.
Thanks.
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