1999 Yamaha 200hp 2 Stroke Power Loss

Daghda · 11 August 2011, 19:41

This is a first time post for myself due to the fact that I have recently got my hands on a RIB. She is used as a dive boat so she is not abused or used a whole lot for most of the year. Due to this I figure she has been somewhat neglected before now.

My problem is this, I do all the necessary startup procedures and she starts up fine and will idle just nicely. However, when you go to power after a little while she suddenly drops to idle and then will cut out.

Now after this happens the fuel line has to be re-primed, and again she will start up fine and move off grand but the same problem arises. What could the problem be? Degraded fuel line, fuel pump or what.

Nos4r2 · 11 August 2011, 23:27

Air leak in the fuel line or water trap, or fuel pump at a guess.

Welcome to Ribnet

Daghda · 12 August 2011, 20:14

Thanks Nos4r2, the fuel line is my first suspicion due to the fact that when I asked when it was last changed the reply I got was "eh, well I don't think it has". The only thing is I am only getting to grips to dealing with the boat mechanically and was wondering is there any pit falls I should watch out for when changing it.

Nos4r2 · 12 August 2011, 20:29

Not really, apart from the fuel in the old line and if you're using jubilee clips on it make sure they are 100% a4 stainless.

Dry Run · 13 August 2011, 07:47

Just a thought, but I had exactly the same problem on a Yam. Tried everything including connecting to the computer, compression test, fuel pressure test, running off a remote tank, etc. It turned out to bew none of those things and was driving me crazy.

Eventually the problem was solved when we found that the trim sensor was stuck (corroded) and was indicating that the engine was fully trimmed up (you could see that on the trim gauge). Once freed up and showing trimmed down the problem simply went away!

As I say, just a thought.

willk · 13 August 2011, 09:41

Hello Daghda

I had similar trouble once upon a time. It was air entering the system at a fuel filter seal. It was tricky enough to locate as I had a fuel line splitter, underdeck lines, primer bulb, filter and fuel switch on the line. After some farting about, I hooked a plastic tank straight to the engine using a spare primer bulb for the join/connection. It ran perfectly and it was a relief to know that something (fairly) simple was the problem, i.e. not the engine. After that I just added each element back into the supply line until the problem reappeared.

Daghda · 13 August 2011, 16:09

Thanks for the help guys, I am just gonna strip out the fuel line from tank to OB and replace line, bulb, NRV and connectors. This may not resolve the issue but the line has never been changed so it has to be done. I was on board her today and I am pretty confident that she is drawing air.

If it doesnt work I will be back on here crying about my failure.

outboardtech · 13 August 2011, 19:06

Hi, OK this engine is a two stroke V6 right. CARB model or HPDI?? Send me the model number and serial number of the OB and I will be able to identify it etc and we can go from there. trouble is knowing the EXACT model and year and fuel system, igntion system and ho it all works can then diagnose a problem. I cant at this stage even start without knowing the model and system. cheers Barry

Daghda · 13 August 2011, 19:22

Well outboard tech this is the info I have on her from the clun tresurer he took down this for insurance purpose so it maybe a bit muddled up.

Yamaha 200 Feto 666 I 351189U
200hp V6 2stroke

Actually I have another question in relation to the fuel line. The setup within the console is tank, primer, separator and then another small filter. I have attached a photo but the doesnt show the second filter, what I want to know is this normal.

Daghda · 17 August 2011, 16:21

Well I replaced to fuel line from tank to engine and inspected the filter. I am glad to say that she is running far better than before. However, I was pretty pissed off when I stripped out the old line. The engine is a 2.5l V6 2 stroke that produces 200hp. So I was a bit surprised to find a 5/16" fuel line connected in between to short lengths of 3/8" fuel line. Whats more annoying is that the source of the air getting in was a connection between the two different diameter fuel lines that was deep within the protective hose which ran down the deck. I am only hoping that this is not the start of a long line of engine issues.

Thanks guys for the advice I really do appreciate it.