location of fuel supply valve and fuel filter on Merc 8.1 DTS

SeaGreg

SeaGreg

New Member
Aug 2, 2015
79
Miami/Keys/Bahamas
Boat Info
2008 38 Sundancer
Engines
Mercruiser 8.1 DTS
So I am a complete rookie here with what I am trying to accomplish on the boat I purchased, I want to diagnose and fix as much as I can without having to call a mechanic. As stated in Gen Discussion I had my starboard engine sputter out and will not restart. I will attempt to change the fuel filter today for the first time (and hopefully many times in the future). I downloaded the Manual for the engine and found instructions and the graphic for the fuel filter replacement. It suggests to turn off fuel supply valve "if equipped" so I am wondering do I have a fuel supply valve and where is it? Also, most importantly, where is the fuel filter located!?!?

Thanks again for all of your help on this board, I am a rookie so please bear with me as I learn my way around this boat and engines and how to repair/maintain them.

Greg
 
Which filter? Cool fuel 3? If so, starboard side, low forward. No need to turn fuel off to change filter Plastic handle with 3 10mm bolts
 
scoflaw said:
Which filter? Cool fuel 3? If so, starboard side, low forward. No need to turn fuel off to change filter Plastic handle with 3 10mm bolts
Click to expand...

It is the "cool fuel module", not sure if it is "cool fuel 3". Is there another fuel filter as well or is this the only one, other than oil which I have located on top of the engine. I will go have a look in a couple of hours.
 
There are 2 filters in there. You'll need a 10mm socket ,could be a 12mm, extension, swivel, ratchet, needlenose pliers for the cup. Get the filters and they're not cheap
 
scoflaw said:
There are 2 filters in there. You'll need a 10mm socket ,could be a 12mm, extension, swivel, ratchet, needlenose pliers for the cup. Get the filters and they're not cheap
Click to expand...


I was able to locate the "cool fuel" filters (part # 35-8M0093688) on both engines, replaced them both, lots of gasoline flowed out despite locating the fuel valves on the tanks and turning them to "off". Where are the second filters located? Are they part numbers 35-802893T? I ordered two of them and was unable to find them on the engines. Only other filter I was able to locate (other than oil) was for the Kohler generator and the part number and description was on the other side of the filter so I could not see it, will have to get a mirror or do more research.
 
Your cool fuel module shouldn't be that full. The cup at the bottom that you didn't change is what traps the water. Seeing you had all that crap in there, I would empty that module with a suction gun and carefully remove the cup with a pair of needlenose and make sure no water or debris gets by it as you pull it out.
 
Thank you all for your replies! I am a bit mad that I went through the entire process and had no idea the filter disc needed to be replaced. Can I add this filter after installing the other one or is it too late and both will need to be replaced? The Mercury manual I had downloaded made no reference to this filter. I spoke to Mercury and the made mention of this filter either, instead they pointed me in the direction of a canister filter I purchased that I still can't seem to locate on the engine.

Could somebody please send me a link to the manual that is used in Dave's post that has a more thorough diagram for future reference? Thanks in advance for that...

Regarding fuel, the valve did not shut off the fuel flow. I had about 1/4 gallon of gas come out and had to disconnect the fuel line from tank to complete the job. Do I have two faulty valves or was something done incorrectly?
 
I never touch that valve when I change mine. So you replaced the canister filter that attaches to the cover? your good there then. Like I said, suck that module dry and replace the cup filter 35-892665.

Google mercury marine parts lookup and save it. Enter your engine #
 
SeaGreg said:
Regarding fuel, the valve did not shut off the fuel flow. I had about 1/4 gallon of gas come out and had to disconnect the fuel line from tank to complete the job. Do I have two faulty valves or was something done incorrectly?
Click to expand...

Ok - before you take it off again this needs to be addressed. A few things have to be wrong to lose a 1/4 gallon of fuel.

A few things, make sure the blower is running at all times and all power is isolated By unplugging the blue clip connector on the cool fuel unit, I also turn off Anything not needed when in the fuel system. Secondly, make sure you isolate the fuel valve with a screwdriver like Dave S post explains - IMPORTANTLY - there are sometimes two fuel solenoid a on the tank, one is for the gen set - trace the line or isolate both in the same way, third have a can or metal container to store any fuel an filter case.

This is personal choice and most will not do this - but in your case with flowing that amount of fuel I would do this now - I would have a plug handy of some kind to plug the fuel line to the cool fuel unit, a screwdriver is what I use for this fuel line, it needs to be about 3/8 diameter. If I am messing in this unit I take off the fuel line going into the cool fuel unit and plug the line and clamp the hose clip to secure it.
Once that line is clamped you can change teh filters and start to see why you have leaking fuel. If you isolated the solenoid correctly you should have only a little fuel coming out of that line.
 
Last edited:
With the ignition off that electric fuel valve should also be off. It can be bypassed and manually turned on , which is what he probably did.
 
sfergson727 said:
We are talking apples and oranges. He is asking about the canister filter, not the cup. Gen III cool fuel units do not have the canister in addition.
Click to expand...

There are 2 filters located in the module, 1 cup and 1 canister shaped filter that attaches to the mod. cover.
 
scoflaw said:
With the ignition off that electric fuel valve should also be off. It can be bypassed and manually turned on , which is what he probably did.
Click to expand...

Maybe - I would rather he was safe tho - sure you agree.
 
So after replacing both cup filters on both engines (no filter discs as previously stated) I ran her for 15 minutes at idle, at the dock, and with everything working well decided to push off for the first time to take my maiden voyage. For an hour and a half she ran perfectly, got her up to 30mph, temps and oil pressure was perfect on both engines, life was good. Shortly after that (about 1.5 hours into the cruise) I lost starboard engine, once again sputtered out. I decided to turn her around to take her home on port and lost my flag as the wind was strong and the wakes from other boats passing in the Biscayne Preserve were tossing me around. It took 10 minutes to recover the flag getting bounced around and as soon as I get it onboard and start to head back to dock on port, port sputters out too. I drop anchor and call TowBoat U.S. (getting my moneys worth for my membership). I ran the generator for the hour tow home and no issues there with stalling out.

This is clearly a fuel issue, can it be so contaminated that it is clogging my filters so often? What is the next step I should take? I have a feeling that if i go and try to fire her up now she will start up, just like the last time after she lost power to starboard, and probably run for a bit before this happens again. Still stumped as to where the Outboard I/O Water Separating 25 Micron Fuel Filter Only 35-802893T goes and whether or not this will help my issue. I see some members say I have this and others say I don't. Mercury told my to buy this as one of the maintenance parts but it does not seem to be on my engines.

Also In this process I had other non related issues I will post separately. As always, thhank you all for all of your help!

IMG_4348.jpg
 
SeaGreg said:
So after replacing both cup filters on both engines (no filter discs as previously stated)

This is clearly a fuel issue, can it be so contaminated that it is clogging my filters so often? What is the next step I should take?
Click to expand...

SeaGreg - fuel that has been sitting for two years is bad news all round. Not that it matters too much to the actions you need to take ...... but how much new fuel did you put into each of the tanks when you filled them up, in your other thread on gauge problems you do not mention this but I assume you have filled up.

Anyway - unless I am missing something the cool fuel unit definitely has the filter disc at the bottom of it. If you have not done so I would definitely open both CF units up again - as scoflow has said - use some form of suction cup and make sure you clear everything out of the bottom of that filter chamber until there is nothing left. As I said earlier if you cannot stop fuel flowing for whatever reason take off the fuel line and plug it while you do this (if fuel is still flowing there is some other issue but not related to the stalling). Then replace those two disc filters - one at at the bottom of each CF unit chamber.

SeaGreg said:
Still stumped as to where the Outboard I/O Water Separating 25 Micron Fuel Filter Only 35-802893T goes and whether or not this will help my issue. I see some members say I have this and others say I don't. Mercury told my to buy this as one of the maintenance parts but it does not seem to be on my engines.
Click to expand...

I think this has been cleared up but just to be clear - there are two filters inside the chamber of the Cool Fuel unit, one disc filter at the bottom of the chamber that you need long nose pliers to pull out (if this is black with crud it is very hard to see), the other is the cylindrical filter that sits in the lid portion of the chamber on the Cool Fuel Unit. Both of those are in series for fuel flow so both MUST be changed given the problems you are experiencing.

The third filter that has been discussed and you are confused about is a "Cannister" and IF you did have one of those it is a fuel water separator and it would be easy to see as it would be upstream of the cool fuel unit between the solenoid valve on the fuel tank, and the cool fuel unit - every boat I have had it has been mounted close to the fuel tank. It looks like when I searched your engine serial number online that you DO NOT have one of those fitted in your boat and that the Sea Ray dealer has misled you. If for any reason that you did have one of those fitted (special order by first owner or an after market) it would be visible to you.

Once you have cleared up the filter issue - depending on how much fresh fuel you added to the bad fuel, there may be some other steps with the pumps or fuel tank flushing.
 
Last edited:
Describe what the filters looked like and the fluid in the module. Water? rubber particles?. How much fuel is in the boat now?
 
Canister filter for the genny? That is what I have, a separate fuel line from the starboard tank though a canister unit to the genny. So while unrelated to the engine issue, a necessary filter nonetheless.
 
Hello all, pardon the late reply, I have been onboard fixing things... to answer your questions:

The port fuel gauge was not working prior to fueling up. I added 75 gallons per tank, port shows full tank still and Starboard about 7/8ths. The vessel view did show port deleting a few times but as of now it is back at full. I did not cover enough distance to see if the fuel gauges will start to deplete.

The filter I replaced is the Cool Fuel 3 "cup" filter. It is a paper cylinder that goes into the cylinder in the lower port side of the engine facing aft. I purchased the disc filters but have not installed them yet.

The fuel that came out of the filter and module did not appear to have water in it but it had a lot of debris, not sure what it was but it looked like various sized pieces of lawn clippings. I have no way to confirm the substance. I will say though that the filter disc caught my attention before I knew what it was and that it was replaceable as heavily soiled and almost moldy looking. It had a ceramic appearance to it through the gasoline. I thought it was some kind of material similar to that found in a brita filter based on appearance. Now that i have seen the disc filter in new and pure form I realize that it was heavily soiled and is in need of replacement.

What additive should I add to the engine and how much of it should I add?
 
Last edited:
You must log in or register to reply here.

Forum statistics

Threads
113,218
Messages
1,428,821
Members
61,115
Latest member
Gardnersf
Back
Top