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Old 08-24-2013, 07:44 PM   #1
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Default Where to mount fuel/water separating filter in 1800MX?

Hello all, has anyone added one of these to their 1800MX model? It's the 3.0 mercruiser model year 2006. I hear these things can help a lot. especially since it's getting harder and harder to find Ethanol free gas in my area. I'm just curious how to mount it. It's a pretty wide open engine compartment with no side walls basically. I'll probably have to make a bracket to mount it to. Also, Unrelated question: Anybody have any vapor lock issues with this motor? My fuel feed line goes right over the top of the valve cover. I asked a merc tech over the phone, as well as my local mechanic. It never used to do this to me, but now it's all the time. I have yet to check my fuel filters (replaced last year is why) as well as check the carb seals for leaks. Which may attribute a little to this problem. Since it's a little more tempermental this year. Had the carb rebuilt last year as well, and a tune up last week. I just cant believe after 5 years of ownership I now have these vapor lock type issues...Thanks!
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Old 08-24-2013, 09:13 PM   #2
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First welcome aboard.

I would look for an area near the fuel pump as the filter/water seperator should be between the tank pick up and fuel pump. If not mounted directly to the engine rubber flex line on either side is required for vibration issues.

Regarding vapor lock get an handheld IR thermal gun and measure temps where the fuel line is routed all should be < 100 degrees F. You may want to check t-stat housing and exhaust manifold as you may be on the verge of a bigger cooling issue. Just being safe here but with 5 years of no issues and now this tells me something is going wrong.

BTY: when was the impeller last changed?
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Old 08-27-2013, 04:06 AM   #3
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Thanks! I just changed the impeller last month, and it always stays right at 175degrees no matter how long it runs or the speeds. Everything I read about the vapor lock is that the heat soak after running is what makes the fuel boil. Are you saying check the temp when its running or after it sits for a while? Probably both would be good, eh? The thermostat would be good to check out, havent changed that ever that i can recall.. The first time it happened was last year after a local shop rebuilt my carb, (suspicion arises about the rebuild job) How about rerouting the fuel feed line UNDER the engine to get it off the valve cover? Anybody ever do that? LOL Regarding the filter, a little bracket may be needed since its a pretty wide open engine bay. That corner of the floor is tempting to bolt it right in to. But probably would stress the fiberglass and mess it up, or be too thin to hold it sercurely. Thanks for the advice. I will defeat this issue before i winterize it! I love to float, and lock through, and not have to ,when it feels like it!! Happy boating Mike thanks again!
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Old 08-27-2013, 11:41 AM   #4
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Is the fuel line running from the fuel pump to carb metal or rubber and do you know if it is ran the same way now as before the rebuild? i.e. did the mechanic change something. I believe most merc engines use metal betweent he pump and carb. How close is the fule line to the exhaust manifold? If the manifold is old it may be getting clogged and increasing it's temp. Yes check temp while running and right ( few minutes) after turning off. If you are running at 175 then I don't think the t-stat is an issue. Need to focus on temp were fuel line is routed.

Running the fuel line under the engine will increase the lenght of the line and head pressure (force required to raise the fuel higher) required to get fuel to the carb, i don't recommend this.

Now that you have said the issue didn't start till after the rebuild and does it all the time I wonder if the rebuild was done correctly as you mentioned. Have you looked to verify the choke is staying open till the engine cools down?
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Old 08-27-2013, 01:57 PM   #5
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Chevy,

Agree with Mike - if the engine running at 175 with little to no fluctuations the t-stat is fine. Don't mess with it. Also on the same page as Mke; did the hard-restart issue start right after the carb was rebuilt?

You might want to descibe exactly under what circumstances the symptom presents itself. As in, "engine starts fine when cold, but after it gets up to operating temp, and I shut it down, then try to re-start within a few minutes, it's hard to start. If it sits for 30 minutes it starts fine". Etc, etc. Since we can't see it from here more details = better internet troubleshooting.

If you suspect a vapor lock condition, and if you can easily induce/reproduce the symptom, I would pull the flame arrestor when you know the engine won't start and look at the choke like Mike suggsted. If it is open, with the engine off have someone operate the throttle while you look into the top of the carb to see if there's a squirt of gas from the accel pump.

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Old 08-28-2013, 02:09 AM   #6
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Alright guys I have some things to try/check out next week when I go out again. It's fine when starting cold, no throttle pumps or 1/4 throttle starts needed. That is needed to start again when warm. It starts right back up in neutral after a minute or two. But I'd say after sitting longer than that it just cranks and wont kick over. I need to look in there to see if it's getting fuel. I believe the fuel line is metal under the rubber. Whatever the oem line is. It sits right on top of the valve cover going straight across the top of it. Always has as far as I remember. I think I saw a volvo 3.0 engine and it had the fuel line going around the front of the valve cover? It was fine after that first time last year that it stranded me. I think that was the second outing after the rebuild. I did let it sit for a good 3 weeks before i messed with it after that. So hard to replicate issues after I let it sit that long.....Probably after an hour it starts. But was better one day when i left the engine hatch open while tied up with a friend. Still took some persuading though. Thanks guys! I'll report back Monday night since I have to work all weekend
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Old 08-28-2013, 01:51 PM   #7
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I wonder if the ignition module is getting hot, causing an open, then closing again once it cools.

Only thing I can recommend at this point is to do your best to replicate the symptom next time you take the boat out. Run it on the water for 30 or 60 minutes to ensure everything is heat soaked. Shut it down, wait for maybe 60 seconds and try to re-start. If successful, shut it down again and wait for 10 minutes then try the re-start. If it doesn't start, pull the arrestor, make sure the choke is open, look for a pump shot, pull a plug wire to make sure it has spark.

Does this engine have the TKS system?
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Old 08-28-2013, 04:49 PM   #8
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That's the plan on Monday, It will start again after 1 minute. We went skiing 2 weeks ago and didnt have any issues. But after more like 10 minutes it'll probably not start. Unless I leave the hatch open and idle it with the blower for 5 mins before shutting off. Which is what the guy on the Mercruiser support line told me to do to combat a vapor lock situation....Even then you have to persuade it by giving it a little throttle in neutral while cranking. Yes its a TKS model. I also need to check my fuel filters. My supposed Mercruiser mechanic at my local shop didnt even think I had a fuel filter in the pump housing. He thought it just had the one going into the carb. I had to tell him to "humor me" and take the fuel pump apart to look for the filter in there! Lo and behold it had one. I will find a new mechanic I think! LOL Should I get one of those spark tester things to check it, or just hold it by metal (holding it with pliers, of course LOL)? Got into some lower water on the Mississippi on Sunday and gnarled up the prop a bit. Oh what fun that was!! Thanks ss3964speed. I used to have a 70 chevelle. Thats where I got my name from! What kinda car do you have with a 396 in it?
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Old 08-28-2013, 06:31 PM   #9
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TKS (turn key start) has a thermal sensor on the carb that tells the priming circuit (replace choke with a injector like thing, yeah I know real technical here) when it's cold and provides extra fuel. When hot it should not but if it does may flood engine and not allow it to start. Just a suggestion.
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Old 08-28-2013, 07:39 PM   #10
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Good (enough for me) explanation on the TKS system, Mike, and is why I asked if it had that. Rule out a TKS problem by getting the engine warmed up and then disconnecting it.

Chevy, the car is a '66 Impala SS. Originally a 396 but now has a roller cam 489.

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Old 08-29-2013, 12:11 AM   #11
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That makes sense, another thing to troubleshoot on the next voyage. Today the heat index was 109, here next to davenport,ia! Nice car Dan!!
Thanks guys,
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Old 08-29-2013, 12:54 PM   #12
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Good luck with it Geoff, keep us abreast of your findings.

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Old 09-03-2013, 08:47 PM   #13
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Well, made it out yesterday. But didnt have a chance to troubleshoot like I wanted to. I did shut it off a couple times. (while it was tied up to another boat) And after 20 mins it started up fine. But after another 20 mins or so I had to give it one pump and 1/4 throttle to start it. Same thing later in the day. That first time I did let it idle a good few minutes with the blower on before turning it off. And it was cooler out then too. So nothing to report yet that could be of any help. Thanks again guys for all your input!
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