4.3l Mercruiser Starting Woes

1994 4.3 Vortex Mercruiser, Alpha 1 outdrive, Gen II
Engine Serial OF 421280
Stern Drive Serial DF 457691

After not running for 4-5 days, this boat is a bear to start. Often takes 15 or more cranks, 10 seconds each. Three different mechanics have diagnosed the issue as "fuel boiling out of the lines" due to hot weather, claiming new fuel has to be pumped all the way from the tank.
PS: I live in southern Canada, it gets hot, but obviously southern US folks know heat better than me!

Once started, no issues...can start and stop it all day. In fact, there is really no warning that it is going to start...it just finally does!

Since I tow the boat, I always start it on muffs before heading for the water...embarrassing otherwise.

So,
1) Do you guys agree with the "boiled fuel" story?
2) Do I have an oil pressure switch issue? (understanding that the engine will not start until oil pressure is satisfied)
3) Other...almost done for this year, but next year I want this problem behind me!
Thanks

Re: 4.3l Mercruiser Starting Woes

Re: 4.3l Mercruiser Starting Woes

Hey wood,

I wrestled with this one for a while on mine and it ended up being a bad antisiphon valve. Here is a post I just made on another thread.

180shabah said:

Barchetta,

AS mentioned above, the fuel in your carb is evaporating when it sits for a while. Pumping the throttle helps very little because there is no gas for the accellerator pump to pump. Usually, after a couple of engine revolution, the fuel pump has run long enough to get some gas into the carb and you can pump it a couple more times and it should fire right up. However, if there is any trash in your antisiphon valve that prevents it from seating completely, then gravity will pull the fuel(very slowly) from your lines and pump back down into the tank. It takes your fuel pump 30-45 seconds to displace the air in the lines and get fuel into the carb, And it is very rare that someone actually cranks thier engine this long as it is bad for the starter.

Replace your AntiSiphon valve, and you can also do one more thing. I added a momentary switch that feeds 12v to the fuel pump, press for 5 seconds to fill the carb, pump the throttle, hit the starter, fires right up.

Click to expand...

Re: 4.3l Mercruiser Starting Woes

Good advice, but wondering how the momentary switch is wired...
woody

Re: 4.3l Mercruiser Starting Woes

Woody-jh said:

Good advice, but wondering how the momentary switch is wired...
woody

Click to expand...

12v from dash(fused) to switch

from switch a purple 14ag thhn was run with the main harnes to the engine compartment, Tie wrapped every 12-/- inches.

The ppl/yel wire that feeds the fuel pump was previously cut for testing, so this became my junction point for my new power feed.

Weather tight gel filled crimp connector was used.

Re: 4.3l Mercruiser Starting Woes-Solved?

Re: 4.3l Mercruiser Starting Woes-Solved?

Tonight we pulled and were able to clean the anti-siphon valve. Looked like like dirt particles between the ball and seat. The hose from the anti-siphon to the fuel/water separator was completely dry when taken apart.
Prior to cleaning, we could blow straight through it.

After cleaning, the anti-sipon had tight shutoff when blowing into it. The spring had good force as well.

Re-assembled, and engine started after 1/10th of a crank. Lookin' good, will retry this weekend. Hoping 4 years of frustration trying to start this engine might be behind me.

Thanks for the advice...I'll let you know how it goes, and consider installing the "pre-fuel" assembly for next season.

Re: 4.3l Mercruiser Starting Woes-Solved?

Re: 4.3l Mercruiser Starting Woes-Solved?

"I love it when a plan comes together..."

Re: 4.3l Mercruiser Starting Woes-Solved?

Re: 4.3l Mercruiser Starting Woes-Solved?

180shabah said:

"I love it when a plan comes together..."

Click to expand...

Hannibal Smith! the A team, You're on the Jazz, man!