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Author Topic:   Yamaha 30 loosing power ?
marc monreal posted 07-17-2001 11:16 PM ET (US)   Profile for marc monreal   Send Email to marc monreal  
I have a 30 hp yammy 2 stroke oil injected on my 13ft sport. Once the boat is on a plane the engine bogs down after about 20 seconds and will not power up unless i pump the bulb. To keep the boat on a plane i have to pump the bulb every couple of seconds.The motor only has 75 hrs on it and runs really strong when it gets the fuel it needs. I have replaced all the fuel line fittings as well as the hose. At idle and up to around ten knots or so there is no evident problem. Ive had the engine dynoed and they were unable to make the motor exibit any of the problems i encountered while on the water. The fuel pump is on the #2 carb and has to be purchased as a whole unit costing mucho $$$. if this is the problem. Ive only put 15 hrs. on the motor since i purchased it and all of a sudden im having this problem. Any thoughts would be greatly appreciated. Thanks, Marc
Dick posted 07-17-2001 11:35 PM ET (US)     Profile for Dick  Send Email to Dick     
Check all of your fuel line connections. They must be tight.
Replace the primer bulb.
Is the vent on your fuel tank open?
marc monreal posted 07-17-2001 11:43 PM ET (US)     Profile for marc monreal  Send Email to marc monreal     
Thanks Dick, Ive already done what you mentioned. Any yother thoughts?
Bigshot posted 07-18-2001 09:53 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
fuel pump diaphram. Do not pass go, do not collect $200, go to a dealer and get a new diaphram, should not need whole pump. This can happen from gas additives. FYI-If the bulb collapsed then vent.
fester posted 07-18-2001 04:29 PM ET (US)     Profile for fester  Send Email to fester     
I had the same problem with a 1989 25 horsepwer yamaha. The problem ended up being in the fuel tank. I am not sure exactly what was wrong with the tank. Replaced the tank and have not had any more problems.
Bigshot posted 07-18-2001 04:39 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
forgot about 6 gal tank. Do you have another you can try? Doubt the tank because too much vent the bulb would collapse and other than that even if tank had a hole the fuel pump will pump the gas out. It aint pumping it. Usually I would say connections, but you already did that. Try another tank(borrow one), if still persists, diaphram.
marc monreal posted 07-18-2001 11:09 PM ET (US)     Profile for marc monreal  Send Email to marc monreal     
Thanks guys for the tips.Bigshot i forgot to mention that i also replaced the diaprahm when i found out the price of a new fuel pump. I havent tried changing out the fuel tank, but i'll try that next. Any other thoughts? Thanks, Marc
CIELO3428 posted 07-19-2001 06:24 AM ET (US)     Profile for CIELO3428  Send Email to CIELO3428     
TampaTom posted 07-19-2001 09:20 AM ET (US)     Profile for TampaTom  Send Email to TampaTom     
I'm having exactly the same problem with a 30HP Tohatsu. We are taking the boat to Steinhatch, FL this weekend, so took apart and cleaned the carb last night (engine started this morning). I'm also picking up a new fuel pump(got a good deal, $34). Before I put on the new fuel pump, I'll see if the carb cleaning worked. Next will be fuel line and tank.

Meantime, I pull the choke out a bit to adjust for the fuel deficiency.

Macman posted 07-19-2001 11:11 PM ET (US)     Profile for Macman  Send Email to Macman     
Same problem here on a 70 Yamaha. Replaced the gas tank, and the problem appeared. I have replaced the fitting.............didnt work. I'll be replacing the bulb next. same deal..runs great at idle, once on plane, phffffft.....a few squezees....runs great.
I curse the day that I installed that Tempo tank! Nothing but trouble since...
If it ain't broke...don't fix it!
Macman posted 07-20-2001 07:45 PM ET (US)     Profile for Macman  Send Email to Macman     
Update on my problem...I went out tonite to take the bulb off...and the tank had split at the seam! (Tempo 28 gal) I thought that it was properly vented...I checked it several times on last use. It definitely wasn't split when I cleaned up the boat after fishing last week. Now I'm wondering if the tank venting was faulty, which caused my problem.What a pain that tank has been! I'm glad to be rid of it. Guess that I'll reinstall the old one, and check out a Pate for next season.
Whenever I get really bummed, I re-read the thread on Optimax engines. Makes my problems seem so insignificant.......
marc monreal posted 07-21-2001 07:56 PM ET (US)     Profile for marc monreal  Send Email to marc monreal     
Just an update guy's. Bought a new fuel tank and that seems to have taken care of the problem. Much thanks for all the input. Regards, Marc

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