4207 Fuel Tank Replacement

[Midnightsun]

Wow, nice prep work and overall project. Definitely not for the faint hearted.

Thanks or posting as one day others may need to go this route and your setup is an excellent visual of what needs to be done.

[Lee_B]

The inboard side and top of the tank was cut out with a sawzall using a short blade. The outboard side was cut out with an angle grinder due to the fact that the tank was less than a quarter inch off the hull. The tank was completely free of fuel and a fire extinguisher was standing by.... Not something I could have gotten away with if I was dealing with gas tanks. Also fortunate to be dealing with aluminum tanks and not stainless - cuts easy and nothing in the way of sparks.

[lester7410]

I am gearing up to first replace the starboard tank in my 1988. Both tanks will be replaced under this project. You can be sure that the new tanks will receive 2-3 coats of epoxy/scrontium chromate all over AND receive 2-layers of 1oz (9oz/yd) epoxy/glass matt on the bottom up 8 inches !! I don't think that this necessary step would have been a deal breaker in the expense of building the fine motor yacht that it is.
How much of the top did you have to remove and how were you able to get to the outboard side after cutting the three accessible sides ?

The new tanks will have to be shorter in height but will be increased in Depth from 18" to 22" to regain the 200gal capacity. My 4207 was refitted with Cummins 8.3L's which allows a bit more tank-to-engine space.

[Viper]

Welcome aboard.

Personally I wouldn't glass the bottom of the tank and up the sides, a coating is all you need. If the glass ever separates anywhere, and it can, any moisture or water that gets in will be trapped in there against the tank. That will eventually result in what you're trying to prevent. It's best to mount it so there is a gap between it and the base to allow for free movement of air underneath it so any moisture/water can evaporate.

Good luck with your project. You should start another thread and document your progress as Lee did here.

[bud37]

Source of the post You can be sure that the new tanks will receive 2-3 coats of epoxy/scrontium chromate all over AND receive 2-layers of 1oz (9oz/yd) epoxy/glass matt on the bottom up 8 inches !!

I agree with Viper. Consider the original tanks have lasted since 1988 ( over 32 years ) with nothing. Consideration for ventilation and a dry bottom will go a long way on a properly bonded tank, also, tanks expand and contract, sweat and oxidize, a very tough thing to stay bonded to. It would be great to see how you end up doing this job.....good luck with it going forward.

When you say the boat engines were refitted .....was it gas before the refit or always diesel ?

[g36]

wow what a project