A note of interest regarding the F350 on GW's and the lower unit bullet and lower water intake being in the water 100% of the time. I just pulled my boat and winterized for the season. During the winterization I pulled the strainer off the lower water intake and found it packed with tiny mussels, growth (aka mung) and a few barnacles. I would say that about 70% of the flow path was obstructed.
I complained about this issue early in the season was told by GW that there was not much that could be done and was chastised by some on the site for being too particular. For the record, I have been brushing the lower unit all season to keep the mung off as was suggested by one of the chastisers. From the exterior everything looked great, inside was not. Did it cause a performance problem, no not this year, but what about five or ten years from now. In my book this is a problem. I was able to get all of it off except for what was deep up in the water passage out of reach. This may be accessible by removing the lower unit but I did not take that step. Yamaha says that this is a secondary pick up designed for high speed boats and that in this application even if it was 100% blocked it would not affect the cooling. Good send me a plug to seal it up and block it off then. Also what happens when one of the dime sized mussels comes free and goes through the water pump and then through the engines cooling passages. Not my preference for certain.
Also, a point worth noting. The lower unit drain plug had a lot of growth on it and around it as it is hidden under the intake strainer and hence out of reach for weekly cleaning. When I changed the lower unit oil it was clear to me if you are not paying attention, the mung that grows around the plug if not completely cleaned off could cause a sealing problem with the plug. It is not easy to get a clear view of the seating area as there is always a little bit of oil coming out of the drain even when left open for an hour. I am sure that I/O owners deal with this every year, I just have not seen it before.
I plan on taking this up with GW and requesting a blank plug from through them from Yamaha to close off the intake since they say it is not necessary in the first place. I will post my findings.
I complained about this issue early in the season was told by GW that there was not much that could be done and was chastised by some on the site for being too particular. For the record, I have been brushing the lower unit all season to keep the mung off as was suggested by one of the chastisers. From the exterior everything looked great, inside was not. Did it cause a performance problem, no not this year, but what about five or ten years from now. In my book this is a problem. I was able to get all of it off except for what was deep up in the water passage out of reach. This may be accessible by removing the lower unit but I did not take that step. Yamaha says that this is a secondary pick up designed for high speed boats and that in this application even if it was 100% blocked it would not affect the cooling. Good send me a plug to seal it up and block it off then. Also what happens when one of the dime sized mussels comes free and goes through the water pump and then through the engines cooling passages. Not my preference for certain.
Also, a point worth noting. The lower unit drain plug had a lot of growth on it and around it as it is hidden under the intake strainer and hence out of reach for weekly cleaning. When I changed the lower unit oil it was clear to me if you are not paying attention, the mung that grows around the plug if not completely cleaned off could cause a sealing problem with the plug. It is not easy to get a clear view of the seating area as there is always a little bit of oil coming out of the drain even when left open for an hour. I am sure that I/O owners deal with this every year, I just have not seen it before.
I plan on taking this up with GW and requesting a blank plug from through them from Yamaha to close off the intake since they say it is not necessary in the first place. I will post my findings.