Need Help PLEASE w/ 2004 150 HP Yamah Vmax Carburated

[Surf Dogg]

I recently purchased an 189 B.C. Pro Guide w/ a 2004 Yamaha 150 Vmax Carburated. The dealer did a compression check (all 110), cleaned the lower carb out and checked the lower unit lube before buying. They also started it up on the muffs for me. The first time we ran it we didn't have any trouble except for it conked out once coming off a plane and took a few minutes to get started back up. Since then I put on a new RACOR fuel filter, replaced both fuel pumps, replaced all spark plugs, cleaned out fuel filter screen mounted to motor, sucked the tank dry, and put new 93 octane fuel in.

I have run it twice since then and the same thing has happened both times:

It fires right up but does not seem to idle very good or consistant and had to keep the throttle reved up a little to keep her running. Idling away from the dock it was running a little rough and bogging down a little. I got it up on a plane and right at 3,000 RPM it seemed to wake up and run very smooth. I made 5 different runs for about a mile each fastest being 51mph @ 5,100 RPM. On the 6th run I was cruising at 4,500 RPM and she fell on her face dropping to 3,000 RPM and sounding boggy (almost like it dropped a cylinder or two). I increased throttle and the most it would go was 4,000 RPM. I slowed down to an idle and tried to get back on a plane and it was extremely boggy and would barely plane off. Then after tring a couple more times it got back up and wouldn't go above 4,000 RPM and had obvious lack of power. Took it back home and here I am. Keep in mind this has happened twice now almost the same thing both times. Note it did stay idling at bout 800 rpm at the end of the runs.

I think I have eliminated any type of fuel issue other than cleaning the other 2 carbs. To me it definately feels like it is dropping a cylinder or two at random times cutting in and out but worked best in the first 10 minutes of running. Even when it was running good shouldn't this motor on this hull do more than 5,100 RPM? What is max RPM for this motor?

I appreciate any advice or other things to check on the electircal or spark/ignition side of things with out having to take it to a dealrer/mechanic.

Thank you in advance for any advice! I just want to get this baby running right so I can enjoy it!

[noelm]

the max RPM is dictated by the prop and the motor setup, now as a starter, have you got a genuine manual for this motor? if not, buy one now, redo ALL the carbs, not just 1, buy complete kits and fit and adjust as per the manual, you may need to do some spark testing when the motor has failed. Do a compression test yourself, do not trust the sellers numbers, unless you were there and read the gauge yourself, remove the plugs and have a look at them, are they all the same? this could indicate which cylinders are not firing and why.

[davidkuhlmann]

It still sounds fuel related to me. Did you get any alarms when this happens? If this fuel tank had previously had non ethanol in it and you are now putting in ethanol fuel it will clean out the tank and clog up the filters continously until it is actually cleaned out. Check your filters again and see if there is any sludge in them. Fuel problems will not usually set off alarms. Do a Google search for ethanol problems in outboards and you will read for days. And yes you may have to take down the carbs again to clean them too.

Also ethanol will eat the inside of the fuel lines and cause them to become a flapper valve of sorts which also could be your problem. Make sure you have ethanol resistant fuel lines, if not change them.

Edited August 10, 2011 by David Kuhlmann

[Surf Dogg]

Thanks guys. I didn't get any alarms. The compression check was done in front of me. Sounds like I will work on these carbs for a start. If the boat is propped right what should the RPM's peak out at ?

[Cracker Larry]

6000

[Surf Dogg]

6000

Thats what I was thinking...I knew it had more left in her

[Woodsie]

You will find the max RPM's to be 5500.

It sounds like carburetor cleaning to me too..

The Ethanol issue made a number of my fishing friends VMaxes run poorly and not at all.

rebuild the carbs, check the bulb and fuel line, and do the filters. Dump out the main filter and see how much crud is in it. If it is half full of gook or better, you will have other housekeeping to do in the fuel system..

Good luck, and be patient. That VMAX will be a brutish motor when you get clean fuel in it !!

Woodsie