yamaha F100, 2000 model has vacume leak.

[bill_m81]

Hi, ive had this engine for 4 months and it has not left the work shop because the mechanics cant put their finger on the problem even the yamaha technicians have been out with their special gizmo's and still have not determined what it could be other than the fact the their is a vacume leak somewhere. Ok, so here is the problem! When I bought this yamaha F100 2000 model four stroke carby engine, it only had 60hrs on it because it was in storage for 6 year (which could of been part of the problem). When i took it out i found that it idols perfect, but it starts to cut out at approximetly 2400 rpm and it continues to cut out until it reaches approximetly 3000 rpm. After 3000 rpm it picks up and goes perfectly. It became an elliminating **** at the work shop, trying to elliminate all the possibilities. The mechanic changed the fuel and the filters and checked the TPS, He also tested the plugs, then the leads, then the coils, then the triggers. All of this tested ok. We suspected that it was the carbys because we found that while driving the boat in the middle of that faulty rev range, where it cut out, the mechanic would take off the airbox cover which exposed the 4 tubes that connect to each carby and when he would sprayed carby cleaner in each one nothing would happen except when spraying it through the 2nd carby. When spraying carby cleaner in the 2nd carby it would pick up and go normally and the same would happen when blocking that tube with a rag. So there seems to be a vacume leak in the 2nd carby/2nd cylinder. Bare with me coz this is where it gets good! when pulling the carby off it seemed to be ok, the jets where ok and didnt seem to have any blockages. So then the mechanic sent the head away for servicing so they could check the valves. After servicing the head and checking the carby THE PROBLEM IS STILL THERE!!! The mechanic tried something different today, he swapped carby number one over with carby number two(but had to do some modifications first). But when he swapped them the problem swapped, now when you spray carby cleaner in the number one carby it goes good. Can someone give me advice on what this could be. Could it be the carby or is it something else. Please help im running out of money!!!

[boats.net]

May be a plugged fuel filter in carb fuel inlet, number 44 in this link Yamaha Outboard Parts 2000 F100TLRY CARBURETOR 1 Diagram
It fits into fuel inlet fitting on carb inside fuel line.

[bill_m81]

He has checked the filters in the carby they seem to be fine. It definetly seems to be a carby problem although the problem is not visable. He has ordered me a new carby so im waiting for that to come in and will keep you posted. In the mean time, any other seggestions?

[99yam40]

Did your mechanic completely disassemble the carb and clean with some kind of cleaning solution and plow out all passages with compressed air before reassembling or did he just look inside and say it looked clean? It sounds like there is some kind of partial plugging.

[bill_m81]

F100 carby problem solved.

I am pleased to say that my boat is finaly fixed. Once he put a new carby on it the problem went away. Servicing the carby was doing anything the whole carby had to be changed. Time to get back out there and catch me a fish.