Mercruiser 4.3L, start, runs 20-30 seconds, shuts off

[kevindtimm]

As in the subject line, those are my symptoms - with the addition that manipulating the throttle has no affect. It runs for a set length of time and then shuts off. All of the reading that I've done seems to indicate that it's an oil pressure safety switch that has failed (though I'm wide open for other suggestions)

It ran fine last year (didn't they all) and this is the first start of the year.

One question, if it is this switch - where is the darn thing located? The boat is about 8-10 years old (it's a Tahoe Q3) and this is a replacement engine (PO bought it, had it fail and so got a replacement engine).

One more thing - the gauge on the dash reads good oil pressure 40PSI give or take.

 

[Scott Danforth]

On block near oil filter boss

 

[kevindtimm]

On block near oil filter boss

Thanks - I will check it first thing tomorrow.

 

[Maclin]

Looks like a gauge "idiot light" type sending unit but will have 2 terminals.

 

[kevindtimm]

yes, I'm aware it's been more than a month - but, life

Anyway, I haven't had time to get out back to look at the engine - am I correct in assuming that it's relatively easy to get the rear cover off the back of the boat (2005 Tahoe Q5)?

 

[bruceb58]

yes, I'm aware it's been more than a month - but, life

Anyway, I haven't had time to get out back to look at the engine - am I correct in assuming that it's relatively easy to get the rear cover off the back of the boat (2005 Tahoe Q5)?

You've never had the engine cover off?

 

[kevindtimm]

You've never had the engine cover off?

Correct, I have not. It's a 2004 Q4 Tahoe Fish & Ski.
To be sure we're speaking of the same thing, it has a cover over the entire engine compartment behind the rear seats - that's the engine cover I'm speaking of (not something integral to the engine itself)

 

[kevindtimm]

You've never had the engine cover off?

The temperature in TX finally dropped to an area where I could work outside for more than 5 minutes without heat stroke and so, I opened up the rear hatch, contorted myself into a pretzel (not a pretty sight with someone my size) and poked around the oil pressure gauge.

Lo and behold, one of the connections was loose (hanging free)! I plugged it in, grabbed the keys and fired the engine. Not surprisingly it ran for over 30 seconds (quite a few minutes). I took it out on the lake and it runs like a top.

I always feel that it's important to close these issues when they close and I'd like to thank the membership here for helping.