Problem w/ 98 150TRLW Carbed V-max

Well, I am new here and things aren't good with my boat. I am hoping that a service guy or someone with the knowledge can help me out. Strap in, here we go...

98 150tlrw carbed engine.

Problem:
Surging, at speed motor will surge. Not seeing increase on tach just in the seat of the pants.
Bogging, at take off boat will not jump up on plane. This just started this past weekend.
Loss of top speed, normal top speed for boat is 58-60mph, yesterday I could not get it over 50mph.
Running rough, at idle the boat sounds rough there is a sheen in the water as if I am loosing gas or oil into the water. 2 weeks ago I cleaned under the motor in the cowell and I am not seeing any new drips.

List of checked items and repairs.
Carbs rebuilt last year.
2 sets of plugs last year.
Fuel filter replaced.
Fuel lines checked. (no issues)
New fuel pumps 2 years ago. (checked those and no leaks)
Sparks coming from all 6 plugs when checked.
New water pump this spring.

I am not sure where to go from here... ANY help would be greatly appreciated.

Re: Problem w/ 98 150TRLW Carbed V-max

Monitor fuel pressure/vacuum at problem RPM. Spark and timing also, but this can be dangerou at those speeds. Would be best to use Yamaha test prop so I does not have to be moving to load motor up during testing. Check for fuel pump leaks internally.

What was done last year could be a problem again this year

Re: Problem w/ 98 150TRLW Carbed V-max

Thanks for the quick reply...

I did check the Pumps, took them off and squeezed the ball to make sure there were no leaks coming out the back of them. They checked out good.

One thing i forgot to mention that you seem to have covered... the problem is only when under load. I can not replicate it in the driveway.

correct me if i am wrong, all firing and electrical signals sent to the plugs is done by a computer that is powered by the stator... is that correct? could any of those parts cause these symptoms?

Re: Problem w/ 98 150TRLW Carbed V-max

If you are losing spark to one or more cylinders , then yes it could be something in the ignition system. And it all can be tested with the proper test equipment. Not sure what all that motor has on it, but maybe some sensors could be a problem also
It is always best to test everything you can and if all is in spec and no problems found then clean carbs again and do the link and sync after reinstalling.
A Yamaha service manual is the best money spent if you plan on working on it yourself

Re: Problem w/ 98 150TRLW Carbed V-max

99yam40 said:

... then clean carbs again and do the link and sync after reinstalling.

A Yamaha service manual is the best money spent if you plan on working on it yourself

Click to expand...

Great idea... are the steps for the "link and Sync" covered in the service manual?

Where could I find a digital copy of the manual? I can imagine that they are pretty expensive right?

Re: Problem w/ 98 150TRLW Carbed V-max

yes procedure will be in service manual

Look up the manual at this site and then punch that # into your search engine to see what all comes up
or order from local Yamaha dealer or online from Yamaha

Re: Problem w/ 98 150TRLW Carbed V-max

Thank you, I will look into a genuine service manual. saw the reviews on the Seloc ones, I think i better stick with OEM.

Thanks again for you help.

Re: Problem w/ 98 150TRLW Carbed V-max

Sorry I meant to post the Yamaha manual site, but something did not work out. Let me try again, if it does not show up then look for it.
http://www.yamahapubs.com/index.do?pg=search&category=4