Definitely check the height of your risers, but also check to be sure you have a flap over your exhaust outlets. Otherwise, when backing down, you ram water up the pipe and into the engine. This also happens at very slow speeds, especially with a following sea. I've seen a lot of boats that have had the exhaust flap removed and a length of hose put over the exhaust port to extend the end of the exhaust to the edge of the swim step or beyond, with no flap on the end. This is just asking for trouble.
If you're going to do that (or if you have that) you need either to put a flap on the end of the extension hose, or a flap unit in the exhaust line inside the boat. A waterlift muffler will serve the same purpose, but they're not a good choice for two-stroke Detroit Diesels, which are exceedingly intolerant of exhaust backpressure. Because they're two strokes, even minimal backpressure will prevent the intake charge from pushing out the burned fuel/air from the cylinder at cranking speed or idle, and they won't start and/or will idle poorly. Some in-line mufflers incorporate a check valve or flap internally; if you don't have flaps on the outlets, you need to use one of these mufflers. This one is really nice, it has a check valve (flap) and it incorporates a connection for an exhaust temperature sensor. This will tell you almost immediately if your raw water flow stops, because the quick rise in exhaust temp without water flow will trip the sensor and alert you to the problem long before you can get engine damage due to no flow through the heat exchanger. http://www.fisheriessupply.com/online/ln_menu/product.asp/Ntt/exhaust+flap/product_id/256984/No/50/mode/1/N/0/Dx/mode+matchallpartial/Nty/1/R/6991/D/exhaust+flap/catalog_name/FISCO/Ntx/mode+matchpartial+rel+Inactive/act/A01/Ntk/All Not cheap, but better than an engine rebuild, which you're looking at if you got salt water in your cylinders. Unless you are very, very lucky, that is. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "UnifliteWorld" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/UnifliteWorld?hl=en -~----------~----~----~----~------~----~------~--~---
