91 Aquasport 175 Fuel leak question

[Hoffman]

Good evening. I have a 1991 175 Aquasport and I am getting fuel leaking into the bilge from the center drain in the bilge. I don't understand this as the tank "looked" to be in good shape when the center hatch over the tank was removed. Furthermore when that floor cover was removed while I was rebuilding it the tank compartment filled up with some water and I needed to pump it out so it would seem to be a sealed section of the boat.  Where does the center drain run as the leak only happens when the boat has the bow up on a small incline or weight in the aft of the boat.

I really hope I don't have to pull the console after all the work we have done to get this far.

[Woodeneye]

Hate to say it but...... If the tank is original and the the fuel compartment was holding water then there is a good chance of there being corrosion/pinholes in the tank where the tank has been sitting wet. It would be prudent to pull the tank and check it. In fact it'd be prudent to replace it if you are going to the trouble of pulling it anyway. That is if it is original. The drain in the fuel tank compartment could be anywhere. Some boats have them others not. It seems a bit random. It sounds like your fuel tank compartment has a drain or a failure aft that is allowing the leaking fuel into the bilge. Additionally I assume you have checked the filler line & it's connections as well as the breather lines? Check the sender seals too.

If it is any consolation there is a lot of information and support on this website to fabricate & replace fuel tanks on Aquasports. It's a PITA job but not that difficult. Worse case scenario you might be running a external poly tank for a while until you get it sorted.

[Hoffman]

Thanks for the input. It did not look like the original tank hence my reason to not pull it. That being said I am regretting my choice.

[Hoffman]

Well it was killing me to find out where the fuel was coming from so I tilted the console and pulled the floor. I found two small pin holes near the fuel sender and grounding  weld. The tank was made by RDS manufacturing which i don't think was the original tank. The question is can I patch the two holes and to put a new gasket on the fuel sender and NOT pull the tank and replace it? Any input would be great.

[mshugg]

Have you inspected under the tank too?  If not, I bet you have other pin holes still hidden from view.  I’m not a fan of stop gap repairs on something as vital as your fuel tank.  It only takes a couple of drops of fuel in your bilge and a spark to make your boat go boom.

[boatnamesue]

Have you inspected under the tank too?  If not, I bet you have other pin holes still hidden from view.  I’m not a fan of stop gap repairs on something as vital as your fuel tank.  It only takes a couple of drops of fuel in your bilge and a spark to make your boat go boom.

He nailed it here ^^^.  Having experienced the exact same scenario of discovering a fuel leak in my AS as you have, after pulling the tank I found pin holes not only in the top but also in the sides of the tank.  Eventhough pulling the tank isn't the news you'd hoped for, it is most prudent.  Unless you don't want to rule out the possibility of leaky fuel tank, thus standing on a bomb. 

[Capt. Bob]

OK,
I'll make it unanimous. Pull the tank. Gas in the bilge??? Been there, done that....... twice.

RDS was in fact an Aqua vendor for the Genmar built hulls. Since you can see the label, it should have all the tank specs including built date.



Good luck.

[jdupree]

X3.  Replace the tank.  You will sleep better at night knowing it was replaced. 

When you put the new tank in the name of the game is keep it dry!!  I know it's impossible to keep moisture out, but make sure that deck hatch is sealed up very well when you put it back down.

BTW, was that tank foamed in?  I am not sure how Genmar installed their tanks?

[Hoffman]

Thanks everyone for the great advice. I have decided to remove the tank as its not worth a patch job and doing all this work again. The tank did not have foam around it so it should not be crazy difficult to remove other than the fact that I just filled it!!!! My OTHER question is that I put a Yamaha 4 stroke 90 on the back and the scuffers are to low which I can fix with a plug BUT if I am replacing the tank would it be smart to do a tank a little smaller i.e 36" long vs 47 1/2 and reduce some weight in the aft of the boat?  I think that should give me close to 25 gallons give or take.

Any thoughts always welcomed 

[Capt. Bob]

You'll get several opinions to this, including this one.

Most will say fit the biggest tank you can so that when you want the extra fuel you can have it. The classic "you can put 50 gals in a 100 gal tank but not vise versa".

Only you know what your boating requirements are. I reduced my tank by 50 gals (from 105 to 55) but I have never regretted it. I know that the way I use my boat, I would never need to carry 100 gals on board at any given time. Such a substantial reduction also resulted in a much reduced cost when I replaced the tank (cost was reduced about 40%) and that savings went toward other boat improvements. Also, with the new tank and fuel lines approved for ethanol, I made a decision to use ethanol all the time. By putting lower quantities in the smaller tank, I manage to cycle the fuel through. Yes I need to fill up each outing and I drain the tank each winter but no ethanol horrors so far.

Your tank is smaller to begin with so you need to ask yourself how much fuel do you really need. I would think the 90 4 stroke is pretty easy on fuel and by reducing the tank length, you can locate the tank further forward to help with the weight distribution.

Good luck.

 

[boatnamesue]

BUT if I am replacing the tank would it be smart to do a tank a little smaller i.e 36" long vs 47 1/2 and reduce some weight in the aft of the boat?

1 gallon of fuel weighs approximately 6.3lbs.  Take the number of gallons your current tank holds and subtract it from the number of gallons for the proposed new tank.  Then multiply the result by 6.3.  For example, current tank is 35 gallon tank; proposed new tank is 25 gallon (35-25=10 x 6.3= 63).  Then ask yourself, will a reduction of 63lbs make a difference, in relation to your scupper issue.

[mshugg]

Back in the day, an OMC  2 stroke 90 weighed 302 lbs.  Now a 4 stroke 90 weighs about 350 lbs.  Seems like the 63 lbs reduction gets you back to design waterline. Or close, anyway.

[boatnamesue]

If the hull weight specs and COG of his '91 175 are similar to a '76 170, I find it strange his scuppers aren't well above waterline.  I've got an engine 100lbs heavier and my scuppers are just above. 

[Capt. Bob]

1992 specs.



1975 specs.

[wingtime]

Absolutely pull the tank and inspect it.  My bet is you will find corrosion under the hold down straps and anywhere on the bottom where anything is touching the tank and/or where water has kept in contact with the tank.  Remember it is OK for the tank to get wet now and then.  As long as it can dry out... no problem.  STAYING wet is the problem.  Either submerged or something in contact with the tank that traps water against it.  This is why I suspect corrosion under the straps and on the bottom of the tank.  This also why foamed in tanks are a bad idea.

As for your scupper issue.  Think of your boat as a sea-saw.  The engine you installed is like a big fat kid on one end of the sea saw.  You need weight up near the bow to even things out or remove weight from the stern or a combination of both. The fuel tank is near the center of gravity of your boat so adding or subtracting fuel won't have as much of an effect.  I'd suggest you get a set of TH Marine ball scuppers.