That's a very good question. I have had an issue with my boat where I bring the boat from speed, into idle and the engine starts to almost quit and then surges up to 2000 rpm's and then will drop down and almost quit again and so on and so forth. I brought it to a mechanic and he's been working on it for 2 weeks now. Replaced the fuel pump and fuel regulator. He checked for vacuum leak. Checked exhaust pressure. Checked ECU and everything turns out fine. ECU isn't throwing any weird numbers. Prior to taking it to the mechanic, I replaced the IAC and the fuel filter. Mechanic send ECU mapping details to Mercruiser. They came back saying that the injectors need to be replaced (throttle body injectors). The mechanic doesn't think that's the problem because the injectors are spraying really well when he watches them perform but he has a used throttle body at home that he's going to put on the boat and see if that fixes the problem. If it does, I don't know how much he's going to charge me (throttle bodies seem to be around $1200 or so), so I thought about seeing if there's a car version of the throttle body. Seems like there are a few parts on a 5.7 Merc that are interchangeable with car parts which are cheaper. Though I'd throw the question out there.
I guess a second question would be, is a rebuild of a throttle body a pretty straight forward fix? I do see throttle body gasket kits go for around $150 or so. Can you just put a new gasket kit on a throttle body and that's considered a rebuilt throttle body?
