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I have a pair of Yamaha 4-stroke 150's that have been giving me trouble after they have been running. They both start just fine at the beginning of the trip, but if I shut them down the starters will turn over for an excessively long time before the motors will start back up. I have squeezed the primer bulbs before I start them back up and it has helped, I just feel that I should not have to prime them every time. I have a 200hp 2-stroke yamaha on an old boat and have never touched the primer bulb.
The primer bulbs have been replaced and both firm up. The bulbs are both located before their respective water/fuel separators (if that matters) and the filters have been changed.
Any wisdom is greatly appreciated!

I the same motors on my boat and have never had to pump the bulbs. Now, I used to have a single 150 Yamaha 4 stroke on my flats boat and it would do the same thing you are referring to, if I had the jack plate all the the way up for excessive periods of time. Could it be a fuel pump issue?

I would start with the vent for the fuel tank. Also, do they have filters under the cowling? With them both doing the same thing, it should be a problem before the fuel splits off to the separate motors "maybe the fuel line it self"

Several different filters under the cowling including the primary filter that sits right at the front of the engine. Yamaha considers it a fuel/water separator filter but is is small. Not had the problem but I did a quick search over on THT and found a several threads where folks were talking about this issue. They also have a Yamaha dealer who contributes check this link out... http://www.thehulltruth.com/boating-for ... ouble.html maybe it will help point you in the right direction as they are talking about a factory mod kit.

captkeyser wrote:I the same motors on my boat and have never had to pump the bulbs. Now, I used to have a single 150 Yamaha 4 stroke on my flats boat and it would do the same thing you are referring to, if I had the jack plate all the the way up for excessive periods of time. Could it be a fuel pump issue?

Possibly, but I think the fuel pumps are located on their respective motors. That would mean that both pumps are going out at the same exact time, not unlikely but when the low-pressure pump went out on my 200, the symptoms were very different.

wevans wrote:I would start with the vent for the fuel tank. Also, do they have filters under the cowling? With them both doing the same thing, it should be a problem before the fuel splits off to the separate motors "maybe the fuel line it self"

I didn't think to check the vent, I'll try there first. And yes, there are filters under the cowling.

Thanks to both!