2005 MerCruiser 4.3L MPI won’t start hot

[spunkyman]

Hey guys.
I’ve read a lot of threads and want to decipher whether I have a vapour lock or perhaps a sensor that’s gone bad. I’m trying to avoid chasing this problem by just throwing parts and money at it ! Facts are 2005 Hurricane SD187 with 4.3L MPI engine. I just bought this Michigan boat with 120 hours on it. Maiden voyage yesterday. I stared it on the muffs in the laneway - tough to start and wouldn’t idle too well. Had to have it in fast idle to keep it running … but then warmed up and ran great.
ON THE WATER
- $50 of fresh gas
- started up and idled nicely.
- ran great for 45 mins and when slowing down, it stalled.
-tough to start again hot. Would have to jam it into gear if it did fire up (which it would at VERY low idle). Most times, it just stalls.
I didn’t get stuck and sometimes I get lucky with a hot start, but it’s running like crap and I’m wondering if these symptoms show maybe a failing sensor or a vapour lock. It’s either starved for air or fuel.
Appreciate any suggestions !

 

[Fun Times]

When was the last tune up performed? Plugs, cap/rotor, flame arrestor, Throttle body cleaned up, water separation fuel filter, engine oil condition checked/changed, engine timing ?

Maybe you have some old fuel mixed with new that is making it run not the best at times along with a bit of water from either past condensation build up or fuel station fill up, (rain/weather, etc.)

Try checking the fuel filter for water or debris as a starting point and maybe run separate fuel supply to see if it cleans itself up to run better.

Engine serial number handy?

Saw you added MPI as I was typing this all out, so I made some changes to this post as well to reflect.

 

[spunkyman]

When was the last tune up performed? Plugs, cap/rotor, flame arrestor, Carb cleaned, water separation fuel filter, engine oil condition checked/changed, engine timing, carb adjustments??

Maybe you have some old fuel mixed with new that is making it run not the best at times along with a bit of water from either past condensation build up or fuel station fill up, (rain/weather, etc.)

Is the Carburetor a Merc Carb or Turn key Start type Carb?

Try checking the fuel filter for water or debris as a starting point and maybe run separate fuel supply to see if it cleans itself up to run better.

Engine serial number handy?

I failed to mention it’s an MPI. I’ve fixed that now. Engine serial is OW318000. Unknown when it was last tuned. New to me. Water separator looks new.

 

[Scott Danforth]

what maintenance did you do prior to putting the boat in the water?

plugs/cap/rotor/wires/plugs?
oil filter & oil
fuel filter?
drive alignment, raw water pump service, u-joint inspection and bellows?

if you pull the fuel filter to inspect its contents, do not reuse.

 

[Fun Times]

I failed to mention it’s an MPI. I’ve fixed that now. Engine serial is OW318000. Unknown when it was last tuned. New to me. Water separator looks new.

Saw you added MPI so I made a few changes in the post above to reflect.

Your engine parts,

4.3L MPI ALPHA/BRAVO - 0W310000 THRU 0W649999

4.3L MPI ALPHA/BRAVO - 0W310000 THRU 0W649999

www.mercruiserparts.com

Need to pull the fuel filter off and inspect the contents, https://www.mercruiserparts.com/bam/subassembly/31501/11705/70

If the tune up that you need to perform no matter the cause doesn't end up helping then sometimes depending on what number drain point system you have, on the 7 point drain, it's been kind of known that the water flow check valve between the thermostat housing and cool fuel pump system has become stuck internally allowing water to flow back to the fuel pump causing a vapor lock like condition... item number 13, https://www.mercruiserparts.com/bam/subassembly/31501/11705/210

If you have a single- or three-point drain system then the check valve is located on the other side of the fuel pump system item number 2, https://www.mercruiserparts.com/bam/subassembly/31501/11705/200

Next time it's running like that, try checking for heated water in-between the T/housing line and cool fuel pump assembly.

 

[spunkyman]

I will look into to these and report back !
Many thanks.

 

[spunkyman]

Ok. I spent some money, did the cap, rotor, plugs, IAC, fuel/water filter and a new idle speed control motor. She runs much better. Idles fine and runs - BUT, after an hour of sitting, she has trouble starting up. I imagine this is the check valve assembly (single drain) part 864206A1 that needs to be switched out ?