Vapor Lock/ Cooling issues

halifax212

Saturday - After my run I pulled up to the flushing station at the marina. I normally bring my own hose but this time there was one there so I used it instead. After a minute or so,  I noticed a steaming discharge of water and saw the crappy hose at the marina had kinked. As well the flow valve on my earmuffs was at 40% amplifying the problem. I quickly fixed the kink and then shortly after the engine started to idle very weak to the point of stalling, but not quite. I shut off the engine and tried to restart, only to have it act like the IAC had failed again.  I brought the boat home and tried starting in the driveway with the same results...3 or 4 seconds of weak idle then stall.  I swapped out the IAC with another I had on hand but the same result.  Next I changed the fuel filter which I had not done in the Spring. I noticed it was only half full. I did not fill the new one before install(I never do) No change , in fact it would not fire.  Some quick research on the site pointed to vapor lock and decided to wait until this morning . 

Sunday - Turn the key and no change.  I decided to check to see if the the gas filter had fuel so I took it off and was only half full. This time I pre filled , reinstalled and yes, it fired almost right away. Problem solved! I am pretty happy with myself at this point with my limited mechanical knowledge.  As I let it idle, I kept an eye on the temp gauge. It seemed to come up fairly quick from a cold start to 160, and levelled off at about 175 which it never does(usually 163). While the engine was coming up to temp, I was feeling the top of each riser and noticed the STB side was warming much faster than port. Even at them the port was still relatively cool to touch. 

Moving forward - What do I throw my money at next?   I feel the impeller is working since there is water flow out of the back. The boat ran fine on Saturday, although when I first started out there was a long continuous beep for 30 seconds and did not return. Engine was not even up to temp at this point.  I believe I cooked the engine enough on Saturday to cause vapor lock but unsure how this has turned into a cooling issue.  

aero3113

I wouldn’t go by those temps since you were on a hose. Put it back in the water and see what it does.

halifax212

I went back out and noticed that the house water was only on a quarter of the way. I cranked it and now the temp stays at 160!   I was the author of my own misfortune on this one I think.  Either way , it has been 6 years since I replaced the impeller on my alpha drive  which will probably improve water flow to the engine.  Will test again next weekend back in the water. Thanks @aero3113

aero3113

Any time @halifax212
6 years, you’re on borrowed time. I would replace the impeller before it fails on you at the worst time.

GMSLITHO

Yep I agree it might have gotten a little chewed up when you had it on the hose at the marina 

raybo3

Call me crazy but I have my impellers changed every spring. Short money for zero problems. (I may have just jinxed myself)

Dream_Inn

raybo3 said:

Call me crazy but I have my impellers changed every spring. Short money for zero problems. (I may have just jinxed myself)

I agree, except I change mine every other year.  But I never miss and always change it after setting for the long winter (in March or February).

prgrod01

The merc manual says no need to fill the fuel filter upon replacement, and there is a mercruiser youtube video that says the same thing... BUT it's a trap. I had the same issue a few years back, did a bunch of work and then the engine wouldn't start. I have throttle body injection so it was easy to see there was no gas flowing, quick fix but my mechanic told me it is a common trap people fall into. Always something to keep you on your toes.