View Full Version : sending unit failure possibly linked to seafoam

02-26-2014, 04:21 PM
In an attempt to remedy what I thought was a carb issue, I began to use seafoam on a regular basis. Shortly afterwards my fuel gauge malfunctioned and would always reflected the tank being empty. I didn't think much of it because I know fuel sending units sometimes just fail. Today, I finally decided to order a new sending unit but before making a purchase I did some research and this is what I found.
Some of you may be interested in a problem I've had with a fuel sending unit on my 1700 Fisherman. Recently I added two cans (32 oz) of Sea Foam to my 26 gal gas tank (2002, Lund 1700), in an effort to help a carburetor problem - per recommendation of a number of Merc. outboard repairmen, and the local Lund dealer.

With a full tank of gas, I took the boat out two days ago and discovered that the fuel gauge read empty. I pulled the floor board and found the tank was full. I pulled the sender (WEMA model UFW 5.5, manuf date 3/13/02) and found that by manually moving the float, the sender was working OK. I then did a series of tests on the float with pure gas, gas diluted with Sea Foam and straight Sea Foam. I think that the Sea Foam lowered the specific gravity of the gasoline and the float was not able to displace its own weight with that additive in the gasoline. The result was that the sender's float apparently sank in the gasoline with Sea Foam added. Evidently this is caused by the plastic material will not floating correctly with a Sea Foam additive.

So, I've decided to purchase a replacement sending unit from WEMA that uses a stainless steel float. I've not received the new float yet, but will follow-up with a post when I get it installed. Hopefully the stainless float will not sink in the gasoline with Sea Foam additive. By the way - WEMA USA is the manufacturer of the sending unit and they have been great to work with, nice folks, good service. There is no certainty that seafoam is the culprit but I thought it to be a heck of a coincidence that I had the same exact experience. Hopefully the new stainless unit will be more durable.

02-26-2014, 04:58 PM
Since Seafoam is basically Pale Oil/white gas/alcohol ... I see no reason why 8-16oz of it would significantly drop the specific gravity of a large tank of gas. And even if it did, why would a different substance float react any differently ??

And if this were an ongoing problem with sending units with plastic floats, wouldn't we have already seen/heard a major uproar about it ??

... cp :kewl

Barnacle Bill
02-26-2014, 04:59 PM
I really do doubt that Sea Foam caused the problem. There are just too many people that use it with no problems.

02-26-2014, 06:21 PM
Perhaps it has to do with the style of float being used. The majority of people are using floats with swing arms whereas the floats used by myself and the guy who wrote the original post are using reed switch floats. Also, we both had floats from the same manufacturer and that particular model has now been discontinued and replaced by a new stainless design. In defense of seafoam, it has been a great additive for all of my vehicles and my previous boat.

02-26-2014, 09:59 PM
I seriously doubt that Sea Foam caused that problem.
My son and I own and operate a small engine repair shop and we use around 2 cases of Sea Foam a week and have for years. We have never had anything but good reports and good luck with it.
It is one of the best fuel/oil additives on the market. We even use it to soak/clean some small engine carbs.
I suspect a hole in the float somewhere....or something else but not just from adding a fuel additive....

02-27-2014, 01:33 PM
If the float you were using has been discontinued I would be willing to think that it could be a design flaw in the float itself. Perhaps others that were not using sea foam were having the same problem when their tank had fuel in it. Ok Chasing Ghost it is ok to use the word fuel isn't it?