Newbie with question about Merc 5.0 I/o in a 2001 Trophy

[Gary47]

While testing the boat for possible purchase, it was completely out of gas at the dealer's dock. We put two gallons in and it started long enough to get to the fuel dock. 40 gallons, then out to the bay at idle for a sea trial. When we got to the channel, we put it in gear and gave it gas, it stalled and died several times. We put it in neutral and revved the engine. Put it back in gear and it died. Did not buy it, but am still interested. Do you think it is a fuel feed problem or electrical? It has the Holley 4412 two-barrel. Thanks for looking.

 

[isaacs]

If it was a regular sounding "miss" and couldn't keep an idle speed it may be the distributor cap. I have to replace mine every couple of years; these engines are known for eating caps. Perhaps the dealer will remove the cap for you--it's easy. If the inside is a bit greasy looking and has some little green boogers hanging from the contacts that's probably all that's wrong with it.

If it's an irregular miss then it has carb problems--probably the result of ethanol in the fuel. In this case a rebuild may not solve the problem and it may need a new carb. I can vouch for that engine, I've had mine since it was new and I don't think I've ever done anything to repair it other than distributor caps. I avoid ethanol whenever possible.

Bob

 

[Gary47]

Bob,
Thanks for the reply. I thought initially that it was the power valve in the carb, but it revved up instantly in neutral. If I buy it, I'll change it to the GM electronic distro . . .this one had the old style distro with external coil. I'll also go with a Holley 600 or 650 4-bbl. Boat is otherwise in excellent condition. .

 

[Rick Stephens]

Something to look at is the shift interrupt switch. A bad lower shift cable can cause the engine to die when put into or out of gear.

 

[Bondo]

It has the Holley 4412 two-barrel.

Ayuh,.... Welcome Aboard,.... I'm gonna guess it's a fuel delivery issue, as the Holley is a Non-Mercruiser carb,....
Merc uses rochester, or Merc-carbs,....
I suggest the Edelbrock 1409 for a 4bbl. which is a carbon copy of the Merc/ Weber that Merc uses, stock,....

The ignition is(should be) T-Bolt V, which is one of the Best ignition systems out there, bar none,....

 

[Scott Danforth]

Mercruiser doesnt use holley carbs, volvo-penta does

if your looking to buy a boat and it doesnt run......then walk away

if your looking to buy a boat with a mercruiser motor and a holley carb, someone switched carbs, what other things did they do? holley carbs do not simply bolt on where the mercarb was

if the boat is a volvo-penta, could be fuel system related.

in either way, if the motor quits going into gear, many times it the lower shift cable and shift interupt

 

[Gary47]

Thanks all for the replies. RE: the Holley carb . . .I did not get a good look because of the air cleaner, but it appeared the same as the Holley 4412 2-bbl we used to run on our race cars. In any event, the reply about the shift interrupt switch was something of which I was not aware. What is the purpose of this?

Learning from the pros . . . thanks iBoat.

 

[RaceCarRich]

Very well could be shift interrupt switch. Quick non-professional overview:

Drive gears are back cut so they don?t pull apart easily. In order to facilitate getting out of gear, when the switch feels enough force on shift cable, this force overcomes spring pressure and triggers the switch to very briefly kill the ignition which takes force off the gears and allows them to pull apart.

What happens is that as the lower shift cable wears, just operating the cable itself gets harder and requires force so even when going into gear, the force overcomes the spring pressure and triggers the kill switch. Since the force doesn?t immediately go away such as when the gears separate, the kill switch is not on for just a brief split second and ignition is switched off when going into gear. Very common.

Easiest way to tell (if not visually obvious) is to put a meter on switch and shift into gear and see if switch completes circuit. I think you can even do this with motor off.

Lots of info on here about this. I figured the pros have explained this a million times so figured I?d pinch hit.

 

[Bondo]

In any event, the reply about the shift interrupt switch was something of which I was not aware. What is the purpose of this?

Ayuh,.... When shiftin' Outa gear, in the water, the switch causes the motor to stumble, allowin' the dog-clutch to release, 'n slip into neutral,....

If the switch moves at any other time, the lower shift cable is draggin',...
The cure is to replace the lower shift cable,....