Yamaha 150 with 21' Seaswirl

Miami-Miami

Recruit
Joined
Nov 11, 2008
Messages
3
Hi,
I am new to your forum but found it informative and the questions and answers are very helpful. Thank you.

This is for a 2004 Seaswirl Striper 2101CC with 150 TXRB Yamaha outboard (Carbureted) purchased used a year a go with 85 hours and now has 145 hours. I have an interesting problem I have not seen in my prior five year ownership of a 150hp Evenrude. This started about three weeks ago.

Only when I am at 3300 RPM or higher, the RPM fluctuates from 3300 to 3400 every about 2 to 3 seconds. Same thing (slight fluctuations of 100 RPM) all the way up to 5200 rpm. I do hear that in the engine as well - so it is not the gauge.

This problem goes away when I am underway above 3300 and someone is priming the bulb?. The problem stays if I oppend the fuel cap (thinking it might be air restriction/pressure holding up fuel from going through).

This started when I filled up the tank for the first time. (yes, at 105 gallon capacity, I never managed to fill up all the way at $4.50/gallon just until now that the prices are down). I thought it was a dirty filter/water separator and I changed it (Racor) ? inspected the plugs and they look good.

Tried the boat and it ran fine for three trips (about half tank). So I thought all was ok and the problem was the fuel/water filter.

Then last week I filled up again and the problem came back..... Could it be a coincidence? Again I primed the bulb when I was doing 3700 rpm and it went up to 3800 and was gone just until I stopped priming the bulb .....

When at idle or slow speeds, priming the bulb does not do anything ? I suspect the fuel pump is OK... but not sure.

I am concerned if I wait until I have half a tank again, I might be hurting this like-new engine (only 145 hours). What do you think?

Now, I am thinking it could be a restricted fuel from the tank due to air lock/pressure, but I since opened the fuel cap while running to see if air intake would help ? it did not.

I am thinking to open the fuel gauge sender and see if I can find something in the tank (doubt it since the boat is only 4 years old), I did read about anti siphon valves but could not find any (unless they are in the plastic tank)

The primer bulb seems to works fine and gets hard with no effort after only 5-6 pump - the motor runs on first crank since I got it and performs perfectly except for this new slight problem (my brother in law thinks I am picky and I should just ignore it).

Am I on the right track or do you think it is a Carburetor, fuel pump issue, or any other issue?

reading your fuel inspection advise, I checked all the fuel lines and they all look good with solid couplings and no kinks. My fuel vent is in the actual Perko cover an there is a second fuel line going to the tank from it. Should I remove all the lines and check them from the inside?

Thanks for all the help.
 

yamamarinetech40

Petty Officer 1st Class
Joined
Dec 17, 2006
Messages
328
Re: Yamaha 150 with 21' Seaswirl

I think you need xanax....you're running yourself in circles here, all over 100 rpm showing on a very sensetive tach....but you could have the carbs rebuilt by top notch tech for a few hundred....and that may or may not change it...notice i say change instead of fix here...since it isn't broken.
 

Miami-Miami

Recruit
Joined
Nov 11, 2008
Messages
3
Re: Yamaha 150 with 21' Seaswirl

I guess you agree with my brother in law then. But he even noticed that it is notthe tach but the negine does make the noise of accelerating and decelarting even though itis only 100 RPM.
if you are saying that it is not an issue - I canwait and see if the change increase to 200 or 300 rpm. And it seems that you are saying it is not fuel related problem but rather Carburator problem - could carb require re-building only after 145 hours - The previous owner and myself use the yamaha oil and the engine never runs bad except for this issue.
Thanks for putting my mind at ease for now - I will keep you posted if anything changes.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Yamaha 150 with 21' Seaswirl

I agree,Xanax and quit the circles.
your describing weak fuel pumps.
by pumping the primer your simply bypassing the fuel pumps.
myself I would clean the carbs and replace the 2 lift pumps and keep boating.
a fuel system vacum test would be good after pump replacement.
 
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