Yamaha V150 VMAX: Lost RPMs and Speed

[BSchwarz]

Got the boat out after fixing the electrical issue and got up to 48mph at 5000 rpm. Not the best its been at but ok. Shut down and went fishing for a bit. Restarted and only go to about 3500 rpms and 30ish mph. Very sluggish. Thinking fuel first as an issue. New pumps installed in Sept 2009 and engine running A+ after a shop made some repairs.

If you have an idea that I should check - shoot me a post - thanks all.




Modified by BSchwarz at 6:30 PM 9/29/2010

[DocG]

Try your fuel filters. Yamaha is famous for having a bunch, I think yours has 3. Also check water fuel sep. if you have one in the back compartment.
Another train of thought would be carbon build up. Have you de-carbed the engine lately? If not go to Wally World and get some seafoam and do that. What oil are you running and what fuel add. are you using with each tank of gas?

[BSchwarz]

Thanks for the chat DocG - I will post with the results in a few days.

I will make the cocktail we spoke about.

[dhagemei]

fuel pressure check at VST tank? Prime bulb (if you could reach it safely)at the exact time the rpm drop?

[fishnhunt]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by DocG &raquo;</td></tr><tr><td class="quote">Try your fuel filters. Yamaha is famous for having a bunch, I think yours has 3. Also check water fuel sep. if you have one in the back compartment.
Another train of thought would be carbon build up. Have you de-carbed the engine lately? If not go to Wally World and get some seafoam and do that. What oil are you running and what fuel add. are you using with each tank of gas?</td></tr></table>

I only have 1 fule filter on my v-max 02 modle

[DocG]

I think you will find there are more than 1. High Pressure, low pressure and fuel water sep. filter. I may be mistaken it wouldn't be the first time but Yamaha is famous for not having the most user friendly fuel system.

[BSchwarz]

Made some changes and heres where I am at: Cleaned out my fuel tank 100% and there was a bit of water in it. Put 16 gals if 91 in, plus Marine Stable and Ring free. Started up in two twiches of the key..NICE. Idles at 650 to 750 rpms, as it has from jump street. Boat is still fluctualing in when I run it but nothing consistant. Sometimes 3200 rpm @29-30 mph, then it might go to 4100 rpm and 39 mph. I checked the throttle cable and it looks good and I think it's a fuel supply issue. Maybe a fuel filter. Next?

[21XDC]

Fuel pump diaphrams, fuel bulb or O2 sensor gone bad.

[BSchwarz]

Thanks - Will check the fuel pumps again for sure, but they were new in Sept. 2009 and the bulb is new in Sept when I had a water seperator installed. I check the seperator 100% gas. Now the O2 Sensor has my attention. Where is it and can I check if it is working?

[21XDC]

http://www.bbcboards.net/zerothread?id=573484

New plugs? Correct ones?

[Rich Z]

Is this a carb or efi motor ? If carb, have the carbs cleaned.

[BSchwarz]

Thanks for the O2 sensor walk through - need to get it printed. The carbs were cleaned last year - they needed it. Plugs. Who might have the right plug types for my engine or know them. I have a 2000 VMAX V150. The plugs were put in by a repair person and I never checked - they might be off.

THANKS for ALL the HELP!

[BuzzB8]

There is probably a small tag inside of the lower cowl (pan) with the plug type. If it's still there, it's probably on or near the back, somewhere you could see it and beneath the plugs.

[fishnhunt]

Factory - there is only 1 furl filter located on the port side of the motor. Sure, there may be more, but from the factory of on 02' modle there is one trust me I have owned my boat 8 yrs.....

[BSchwarz]

Checked the plugs and they appear to be the same ones I had on from last year when I had a few things done to the engine in Sept. Those plugs were recommended for my engine by one Yamaha Marina (NGK R BR7H5) locally . Looks like I paid for new plugs and never got them . And this was another Yamaha Servicer. Found something funny that I never saw before. The terminals on two of the plugs were loose and I thought it was one solid piece going into the plug – they are screw on. Could this be a problem? Either way I am going to get the correct plugs - NGK I here are the best – I had Champions originally.

The boat has one fuel filter after I read through an online manual I found. Thanks Jacob! After the plugs are replaced I will check out the boat and move onto the fuel filter if the problem is not fixed. Then the O2 Sensor. Nice walk through for the replacement of the O2 sensor.

[fishnhunt]

I dont think you have an 02 sensor on your carb motor...I dont have one on mine...Just an FYI. And yes NGK plug tips screw on. Also make sure your orange boots are twisted on TIGHT!

[BSchwarz]

Orange boots? Sorry but give me a clue - I seeming can't but 2 and 2 together on "orange boots".

Stick with NGK's?


THX

[BSchwarz]

Orange Boots - Got IT!!!!

[fishnhunt]

yes stick with NGKS Take you cowling off and usually on the back side port side there will be lable stating the correct plug to use

[BSchwarz]

Well I am on the water again and thanks to all - DocG, dhagemei, fishnhunt and 21XDC. A few mistakes on both my part and the shops. First the faults of the shop who worked on the engine last September 1) they installed the wrong plugs and 2) the plugs were NOT gapped. Several were gap almost at half what was needed. WOW! Several of the plugges were real real nasty and fouled for sure.

My faults are that I never changed the plugs this spring and now remember I should have since a new piston was installed after a cylinder was fixed and second it never hurts to know more about your engine. Lesson learned. Now all I need to do is re-adjust my jack plate and I will be at 60 mpg again.

Thanks all!