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CC2MC
03-30-2013, 12:01 AM
I put the boat in the water for the first time today after putting all plugs back in and changing spark plugs. I started off by backing it in and leaving it on the trailer while I started it up. Everything seemed normal so I went ahead and pulled off and took it on a test run. I set the PP to twenty mph and all is well. I proceeded to go WOT and at about three quarter throttle, it seemed to choke and only made it to 35mph. I opened the engine hatch and noticed a little water, resulting from a loose hose to the transmission cooler but just tightened the screw and was good to go. This fixed my leaky water issue but not my top speed problem. I also checked all my spark plugs to make sure they were all screwed in and all wires connected properly but everything looked good there. I proceeded to call Rambo Marine and they said that it could either be a fuel filter or fuel pump. I have bought the filter for the engine and above the gas tank, but here is my question. Do I need to somehow release any pressure in the fuel line before I change the filter on the engine? Also, if it is my fuel pump, will it hurt anything to run the boat at wakeboard speed which it seems to do just fine? I know eventually I would have to replace it if it were the issue, but I would rather not at this point in time.

jakethebt
03-30-2013, 12:29 AM
To release the pressure on the fuel system, there is a small schrader valve near the fuel filter mounted on the engine. The schrader valve looks like a tire valve stem. You can de-pressurize it with a $20 gage set from an auto parts store or a screw driver and a rag to cover it. Just act like you are letting air out of a tire. Make sure your key is off and battery disconnected first. You don't want your pump on or a spark. Very little fuel will come out from the pressure relief but a lot will come out when you remove the fuel filter. I wrote up a LT1 winterization check sheet and ski-me took some great pics that talk about replacing the fuel filter. Check the winterization section for LT-1 winterization.

gotta_ski
03-30-2013, 01:54 AM
Some of the LT-1s have two fuel filters. Not sure which years do and don't. My 98' has one on top of the tank and one on the back of the engine near the fuel pump. Might as well replace them both while you are there.

CC2MC
03-30-2013, 08:02 AM
Some of the LT-1s have two fuel filters. Not sure which years do and don't. My 98' has one on top of the tank and one on the back of the engine near the fuel pump. Might as well replace them both while you are there.

I did go ahead and get both filters as that is a cheap fix, but Rambo said they rarely replace the one above the tank unless the customer specifically requests it.

I will probably just go with the screwdriver and rag method of pressure release. I thought I had remembered reading something about that. I did not think to look in the winterization checklist though. Thanks for the info.

JimN
03-30-2013, 09:05 AM
I did go ahead and get both filters as that is a cheap fix, but Rambo said they rarely replace the one above the tank unless the customer specifically requests it.

I will probably just go with the screwdriver and rag method of pressure release. I thought I had remembered reading something about that. I did not think to look in the winterization checklist though. Thanks for the info.

I fail to understand how the front filter can become clogged and the rear wouldn't, unless the rear is able to pass larger particles and if the tank someone has larger particles (not impossible), that would clog first. If they're the same filter (GF-626), it would be the rear filter that clogs first, not the one on the engine. The only difference would be in how easy it is to replace.

I would check the fuel pickup tube, anti-siphon valve and fuel cutoff, located at the tank. You posted that you bought two filters and the cutoff is right there with the one at the tank. The fuel pickup tube is the rectangular aluminum block that has the anti-siphon and cutoff threaded into it, just before the filter. If you see anything in the pickup tube, use compressed air to blow it out from the top.

Any time you have a driveability issue, check the fuel pressure. Also, check the screen on the fuel pump. The auto parts store chains usually have a tool loan program- get the kind with the bleeder valve and take a fuel sample while you're checking the pressure, before and after. Changing filters can dislodge things in fuel lines. I would add a can of Sea Foam before changing the filters, too. It can help to remove contaminants, allowing them to be caught by the old filters. No point is killing new ones.

Snipe
03-30-2013, 09:09 AM
Hmmm...Why would the one at the tank not be replaced; that seems to be the first one to trap anything.:confused: Why is there even one at the engine. Am I missing something??

JimN
03-30-2013, 10:01 AM
Hmmm...Why would the one at the tank not be replaced; that seems to be the first one to trap anything.:confused: Why is there even one at the engine. Am I missing something??

These engines really don't like dirty fuel and if you only have one filter, that's your only chance to catch anything in the fuel. If you have two, you'll ultimately have cleaner fuel reaching the injectors. Unless one filter is never changed.

In fuel systems, it's common to use one filter to catch the large chunks with the first one and smaller ones later. Depends on the system and how well contamination is expected to be avoided. I have seen seeds from trees and plants in fuel pickup tubes, so it's not just from what's in the tank at the gas station or whatever is in the gas can.

Table Rocker
03-30-2013, 10:02 AM
Hmmm...Why would the one at the tank not be replaced; that seems to be the first one to trap anything.:confused: Why is there even one at the engine. Am I missing something??
I guess the potential exists for your rubber fuel hoses to degrade and introduce particles to the fuel and fouling your injectors. I believe it is all hard fuel lines after the screw on filter, so it is a good last defense.

SP Maristar
03-30-2013, 10:23 AM
Our LT1 has two in line filters. One here91997and one here. 91998

Snipe
03-30-2013, 12:01 PM
Do you perhaps know the part number or are there different applications?

JimN
03-30-2013, 12:06 PM
Do you perhaps know the part number or are there different applications?

GF626 should work- IIRC, it's rated for 5 micron. At the tank, you can use a 10 micron filter. You don't want to use a very fine filter at the low pressure end (the tank, where the fuel is drawn from because gas' viscosity is such that shear occurs. A good visual for this is a kitchen faucet- the screen in the faucet causes shear, which is how it aerates the water. It's a major case of vapor lock at low temperature and at high temperature, it's even worse.

Table Rocker
03-30-2013, 12:47 PM
My '96 uses a WIX 33481 (http://www.wixfilters.com/Lookup/PartDetails.aspx?Part=33481) screw on filter after the fuel pump and a WIX 33003 (http://www.wixfilters.com/Lookup/PartDetails.aspx?Part=33003) in-line with clamps on top of the tank.

WIX 51061 (http://www.wixfilters.com/Lookup/PartDetails.aspx?Part=51061) is the long oil filter (I thought I would add that while I was looking at my filter numbers).

Snipe
03-30-2013, 01:40 PM
Thanks all. I think this should not have to be marine specific and can pick this up at a local NAPA dealer? BTW this goes on a '98 5.7 Vortec

Table Rocker
03-30-2013, 02:58 PM
WIX 33481 is NAPA Gold 3481 (http://m.napaonline.com/Tablet/parts/PartDetails.aspx?Id=FIL3481_0238827283)

WIX 33003 is NAPA Gold 3003 (http://m.napaonline.com/Tablet/parts/PartDetails.aspx?Id=FIL3003_0397750831)

CC2MC
03-30-2013, 06:41 PM
I got a Puralator F21111 for the tank and F33144 for the engine and yes I got them at Autozone. Unfortunately, I did not have time to replace them and run the boat, bc I had to get back to town, so I guess it will have to wait until next time. I will take apart the fuel pump and check that screen as well. I kind of wish I had run the boat with the old plugs before I changed everything just to see if they could have been the issue, but I would think that new plugs should run just fine.

sethro
03-30-2013, 06:53 PM
I read your post, and what struck me as a possibility is that you said you set PP to 20mph. Did you disengage PP before trying WOT? That would be an easy fix and would mimic a fuel problem as PP tries to hold your speed back.

CC2MC
03-30-2013, 07:01 PM
I read your post, and what struck me as a possibility is that you said you set PP to 20mph. Did you disengage PP before trying WOT? That would be an easy fix and would mimic a fuel problem as PP tries to hold your speed back.

Valid question, but yes I did disengage PP before WOT. I wish it were that easy.

SP Maristar
03-30-2013, 07:04 PM
Our LT1 has two in line filters. One here91997and one here. 91998

The two filters shown here are NAPA 23481.

mikeg205
03-30-2013, 08:02 PM
Try getting ahold of STX221... he had some LT-1 issues... and was able to solve them for cheap.

CC2MC
04-20-2013, 10:11 PM
I exchanged one of the fuel filters tonight just after the fuel pump. I want to check the screen on the fuel pump, but wanted to know where to access the screen to see if I need to clean it. I also need to know if the system needs to be primed before starting after cleaning the fuel pump. Do I need to do anything past turning the key to let the pump come on a couple times? Thanks for the help.