1976 Aquasport 170 - Fuel Troubleshooting

[TooLoose]

First post in some time...
 I noticed a small amount of fuel in the bilge last time I ran the boat and I've done quite a bit of trouble shooting over the last few weeks to try and pinpoint a slight fuel leak. Curious if anyone here has thoughts or direction. Much appreciated.

1 - I put a few blocks under the trailer jack to get the bow really high. Boat sat for about 5 weeks with a half-tank and outside of an initial small pooling of fuel nothing consistent
2 - I filled the tank all the way up, inspecting the vent and fill lines during the fill up... no indication of leak. Also, jacked the bow up and let the boat sit for 24 hours, no fuel.
3 - I ran the boat last Sunday. Everything looked good initially, but after about 10 miles I noticed a bit of fuel pooling in the bilge again. After sticking my head in the bilge, the appeared that the 'drip' was coming from under the tank coffin.

In May, I had the tank pressure tested by a very reputable local company. They said everything tested out well and were very positive on the state of the fuel tank (after scoping). Given all the 'testing' I have to assume that the leak is around the connection point from the tank to the fuel line that goes to the outboard? I only say this because if the tank was compromised I would have expected a continuous leak while the boat was sitting, where I only noticed when it was under power. Does that make sense?

I'm planning to open it up next week... worse case, does any one have information on a tank to purchase as replacement for this model boat, or would you suggesting reaching out to some custom manufacturers? Positives/negatives in using a poly tank this time around?

Thanks everyone

[Capt. Bob]

I ran the boat last Sunday. Everything looked good initially, but after about 10 miles I noticed a bit of fuel pooling in the bilge again. After sticking my head in the bilge, the appeared that the 'drip' was coming from under the tank coffin.
 
I'm planning to open it up next week... worse case, does any one have information on a tank to purchase as replacement for this model boat.

IIRC you stated the hull was rebuilt in 2006 and at that time the tank was replaced. That would make it 16 years old. If installed correctly, it should still have a lot of life left but....
I replaced the factory tank in my 84 CCP in 1996 just 12 years old and highly corroded. I found the leak when the tank was full. Depending on how the tank was secured, water might have found its way between a mounting strap and the tank surface. Crevice corrosion results in pinholes that tend to leak when the tank is full and you are underway. The tank tends to slide against the mounting strap and fuel leaks through the small holes. Without seeing the tank, that's just a guess but there are plenty of pics here showing this type corrosion.

Good luck.

[TooLoose]

Delayed response here... Life got in the way of boat problems.

So I pulled the console and deck hatch to inspect the fuel tank. Unfortunately, the fuel tank was in fact compromised, a few holes likely resulting from inappropriate installation methods, but the coffin is in good structure. I have a new custom aluminum tank on order (same specs as existing 27 gallon tank) and am working with a local boat restoration shop to do a proper installation.

I'll be meeting him on Friday to walk through the install procedures, but based on conversations I understand that he plans to (1) glass in aluminum "support arms" into the coffin and (2) mount the new tank directly to the "support arms that way there are no straps or foam that could expediate any future corrosion. Out of caution, I am also going to be re-coring the deck "hatch."

Anything else this group would recommend I look into since the boat is opened?

Thanks for the feedback.