Carver Owners Forum

Anyone know of the best way to pump out the holding tank in a 350 Mariner? It is located all the way on the top port side of bow and the tank is a good 8 ft lower. When you pump it out normally, it seems to be very VERY slow as the pump out station labors to lift it also probably not allowing it to ever get all of it out. If you own or have owned a 350 Mariner of that late 90s vintage, I'd like to hear your opinion.

Had a mid 1980's Mariner and didn't seem to have the issue you are having. Granted it's a lengthy distance from pump out port to the tank, but may I suggest you check your tank vent. If your vent is plugged with insect debris and you are not getting a enough fresh air into the tank while pumping out you will be creating vacuum in the tank, thus giving you the laboring effect. Also, FYI, we just last season started using a product called Happy Camper and Happy Camper Tank Cleaner and have to tell you the tanks have cleaned up quite well and the sensors are working much better, the boat is 20 years old by the way! Another fault we all seem to have is that we try to use as little amount of water with each flush as we can to prolong pumping out and by doing so we shoot ourselves in the foot be doing so. GOOD LUCK. And I hope a plugged air vent is your issue.

Do you have vacu flush....if so perhaps the vent is plugged. Ours pumps out fine, but we have the electric toilet so it can pull lots of air behind the waste.
Edit.....to add, have a look at your holding tank to see if it is collapsed a bit....there should be tank saver valve in it that stops that if you have the vac flush toilet.

You can always unscrew the tank level sensor on the holding tank and suck it out directly.

I have not issues with my 350 Mariner when we pump out. It empties fairly quickly. This brings into question, what your putting into the tank that might be clogging up the lines.

Interesting, where is the holding tank vent located on a 98 350?

I believe it will be on the starboard side, mid ship just under the gunwale.

This may help, lots of info.....check out owners manual page 178 , drawings of vents, labelled etc ........

https://carveryachts.blob.core.windows. ... ver_98.pdf

grizer wrote:Source of the post Interesting, where is the holding tank vent located on a 98 350?

On my 99 Carver 350, the holding tank vent is a silver vent similar to the fuel tank vent. It is located port side just behind the sink (about midship).

If you remove the dinning room table back seat cushion and unscrew the plastic panel adjacent to the sink you an see the vent line and check to see if it has a charcoal filter that may be clogged.

Yes. If you have a filter in line with the vent and it get clogged it will act as if the vent is plugged.

Thanks for all the great insight! A few of you mentioned and in line charcoal filter with the holding tank vent line. Does anyone have any specific guidance on how or where specifically to add an in-line charcoal filter? Should it be close to the outside or close to the tank etc.?