gas pre heater on a 165?

5 o'clock Houseboat · Mar 26, 2012

I have an 88 merc 165 in a bowrider and it seems ot have a gaas preheater between the fuel pump and the carb. There is a 1.25 inn ch rubber hose labelled heater and it is over a thin gas line. At one end it takes hot water from the rear of the head and at the other end it has a fitting to take water froom the bottom of this hose to the water line going out to the outdrive. the fitting at the outbound end is a 3 inch copper line with a 1/4 inch nipple onn it. On mine the nipple broke off and it had been sodlered. Should it be soldered or is there a part that has it made as one unit without the solder joint? I am afraid tht if I solder it that it will break again.

Bondo · Mar 26, 2012

Re: gas pre heater on a 165?

Ayuh,.... Welcome Aboard,... Got a picture,..?? No idea what yer talkin' 'bout....

5 o'clock Houseboat · Mar 26, 2012

Re: gas pre heater on a 165?

I can get a picture when I go home tonight but I never heard of anything like this and am thinking it may not be necessary. I'll post photos later - thanks

5 o'clock Houseboat · Mar 27, 2012

Re: gas pre heater on a 165?

Don't know if the pictures are coming through as I only see the computer language of the attachments but it should show an overall of he hose marked HEATER HOSE 7/8 and at each end there is a thin metal line coming out attaching to the carb at the top end and the fuel pump at the bottom end. A small water line comes from the top rear of the head into the top of the HEATER HOSE and another one is attached to the bottom of the HEATER HOSE and goes to the water line running to the outdrive. It seems it s only function is to pre heat the gas going from the pump to the carb. I've never seen anything like this and it seems it would be simpler if I eliminated it.

Oshkosh1 · Mar 27, 2012

Re: gas pre heater on a 165?

All I see is heater hose being improperly used as a spliced in fuel line...

Why in the world would you "preheat" gasoline???

Bondo · Mar 27, 2012

Re: gas pre heater on a 165?

Ayuh,.... It appears to be a Cob-job fuel line repair,...

It ain't a fuel heater,...

It appears to be a rather poor attempt at a repair...

RogersJetboat454 · Mar 27, 2012

Re: gas pre heater on a 165?

Busch league hackery!!!

You need to replace that with either a steel line, or proper fuel line. The rubber in that heater hose probably doesn't appreciate gasoline running through it. If I were you, I would also be pulling the carb apart to check for rubber chunks. Who ever did that repair knew just enough to be dangerious....

Don S · Mar 27, 2012

Re: gas pre heater on a 165?

You're probably lucky you didn't blow up.

I would strongly suggest you take your boat to a certified Mercruiser dealer and get it fixed properly. Don't take this wrong, but with your description of the problem in the original post and the pictures, it sounds like you may be a little past your abilities on this one.
You do not want a poor fix on this problem. That is gasoline under pressure in an enclosed area you can't see when running.

boatguya1 · Mar 27, 2012

Re: gas pre heater on a 165?

Almost looks like someone tried to make a "water jacket" around the fuel line to try and prevent vapor lock.

Hard to believe someone would think that is safe if it's full of fuel.

James

5 o'clock Houseboat · Mar 27, 2012

Re: gas pre heater on a 165?

James - you are right - it IS a water jacket around the fuel line and done so well that I was thinking it was stock, but with all of you being as surprised as I was on seeing it I guess it isn't stock. The other posts seem to point to gas been run through a rubber line but it doesn't. The gas is in a metal fuel line that is inside the rubber water jacket. My thought was to simply disconnect the incoming and outgoing water lines so the exhaust water goes from the head to the outdrive and let the rubber "water Jacket" serve as protection for the enclosed fuel line. Does that sound rational to anyone?

Utahboatnut · Mar 27, 2012

Re: gas pre heater on a 165?

maybe the previous owner had some vapor lock issues and (hopefully) just used the rubber as an insulator around the correct hose. Just looking for the best case on this one...

Bondo · Mar 27, 2012

Re: gas pre heater on a 165?

The gas is in a metal fuel line that is inside the rubber water jacket.

Ayuh,.... I see NO water connections in yer pictures...

RogersJetboat454 · Mar 27, 2012

Re: gas pre heater on a 165?

5 o'clock Houseboat said:
James - you are right - it IS a water jacket around the fuel line and done so well that I was thinking it was stock, but with all of you being as surprised as I was on seeing it I guess it isn't stock. The other posts seem to point to gas been run through a rubber line but it doesn't. The gas is in a metal fuel line that is inside the rubber water jacket. My thought was to simply disconnect the incoming and outgoing water lines so the exhaust water goes from the head to the outdrive and let the rubber "water Jacket" serve as protection for the enclosed fuel line. Does that sound rational to anyone?

Maybe I'm missing something in the photos here, but where does this "water jacket" tie into the cooling system? It looks like a strait shot from the fuel pump to the carburetor, with nothing in between....

FYI, you do not want to heat fuel, you want to keep it as cool as possible so it doesn't boil, vapor lock, or even worse cause the bilge of the boat to fill with fuel vapors. Have you actually removed the heater hose from the fuel line to verify that there is a real fuel line inside it?

Don S · Mar 27, 2012

Re: gas pre heater on a 165?

Squeeze and twist the hose, you should be able to tell if there is a steel tube in it or not. :facepalm:

5 o'clock Houseboat · Mar 27, 2012

Re: gas pre heater on a 165?

Here is a shot of the top connection from the Antifreeze reservoir to the top of the gas line and one shot of a close up of the connection at the top of the gas line. The bottom connections are similar except that the bottom connect to the rubber water line was a short piece of copper with a 1/8 nipple soldered on for the smaller line and the line from the block to the outdrive was cut to accommodate this fitting. I agree with everyone about the stupidity of heating gasoline but that is the only purpose that I could think of and didn't know if this was a common feature on this model as I have large crusaders on my big boat and outboards on the smaller ones. This is HER boat and she likes it just the way it is so I have to learn how to keep it going (I've learned that you never want to pi@# off the captain).

Utahboatnut · Mar 27, 2012

Re: gas pre heater on a 165?

Maybe thats where the engineers at merc got the idea for "cool fuel" kidding aside that is a new one on me. I would guess its for cooling (even though the water is hot) rather than heating. That is some kind of vapor lock problem if you have to liquid cool the fuel line. I would remove it and try different alternatives, re route the fuel line, cut vent holes in sides of dog house, spring over the fuel line etc. Keep us up to date this is a very interesting piece of workmanship.

RogersJetboat454 · Mar 27, 2012

Re: gas pre heater on a 165?

Utahboatnut said:
Maybe thats where the engineers at merc got the idea for "cool fuel" kidding aside that is a new one on me. I would guess its for cooling (even though the water is hot) rather than heating. That is some kind of vapor lock problem if you have to liquid cool the fuel line. I would remove it and try different alternatives, re route the fuel line, cut vent holes in sides of dog house, spring over the fuel line etc. Keep us up to date this is a very interesting piece of workmanship.

Depending on the formulation of the gasoline, pressure on the gasoline, atmosphere pressure etc..etc... Gasoline can boil as low as 100?F. The thing cobbled together there could very well boil the gasoline going into the carb.

Honestly, I would remove the whole bit of interesting workmanship, then plumb it as Mercruiser intended it to be plumbed, and go from there. If everything is correct, the fuel system shouldn't require some crazy heat exchange system probably developed by someone who also makes great looking tin foil hats...

Don S · Mar 27, 2012

Re: gas pre heater on a 165?

What's odd, is that depending on where the water is coming from, it could very well be cold water. He does say it goes out to the drive, but I would bet it's cold water coming in from the drive, and the water exits out the exhaust riser. Depending on what is inside that heater hose, it may be safe and actually not hurt anything. I wonder why there was a need for it, but ..................

Amazing what happens when you can actually see something.

Bondo · Mar 27, 2012

Re: gas pre heater on a 165?

Don S said:
What's odd, is that depending on where the water is coming from, it could very well be cold water. He does say it goes out to the drive, but I would bet it's cold water coming in from the drive, and the water exits out the exhaust riser. Depending on what is inside that heater hose, it may be safe and actually not hurt anything. I wonder why there was a need for it, but ..................

Amazing what happens when you can actually see something.

Ayuh,.... Somebody put Alota effort into it.....

RogersJetboat454 · Mar 27, 2012

Re: gas pre heater on a 165?

Don S said:
What's odd, is that depending on where the water is coming from, it could very well be cold water. He does say it goes out to the drive, but I would bet it's cold water coming in from the drive, and the water exits out the exhaust riser. Depending on what is inside that heater hose, it may be safe and actually not hurt anything. I wonder why there was a need for it, but ..................

Amazing what happens when you can actually see something.

Agreed,

Just hope that contraption doesn't contain a standard steel line that's been cooled/heated by salt water...

gas pre heater on a 165?

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