Help Please

SeaRay JR

New Member
Jun 16, 2019
1
Boat Info
1994 SeaRay 7.3 Aft Cabin
Engines
7.4 mercruiser
Have a 1994 250 cruiser 454. Have literally dropped a couple thousand in 2 different marinas who cant figure the problem out. But love my AMEX.

The problem began with one day running 4200 Rms it suddenly just shut down literally it squatted on me like the bottom fell out. it wouldn't start for anything then 30 minutes later drifting along it fired right up and no issue. until again. so I changed the coil and coil wire, now it don't shut completely down and will run but-->

Let me explain, Once the boat is warmed running about 45 minutes it suddenly starts to bog. meaning loss of power and cant get it back over 2400-2600 rms. More throttle will only cause it to back fire.

When its cold no issues I can get it out of the pocket in seconds to 4500 RMS and were flying, then 30- 45 minutes into the run it literally will just begin to lose power and eventually squat on me in the water and cant get back up or into a plain again.

What have I done.

drained the gas tank= new gas
rebuilt the carburetor.
changed plugs & wires
changed coil and wire
changed all gas filters
installed new batteries
changed distributor cap & censor
alternator
water pump

Then we used an override electric start to eliminate the problems north of engine , still same issue.

I am proud to say we run A Sea Ray but frustration is building and has its limits.

Any sound advise is welcome as my wife loves this boat more then me. And is of no mind to even reason or discuss another boat. This is the one and she wants it fixed. :)-

Cheers
 
Possibly old fuel lines collapsing???
 
+1

You need to monitor fuel pressure while running well and when it craps out.
 
Possibly old fuel lines collapsing???

Yes, check the fuel lines, fuel pickup and anti siphon valve. I had similar symptoms a few years ago, turned out the fuel line was deteriorating from the inside, probably exaggerated from using ethanol gas. New fuel line, problem solved. Also, anti-siphon valve can cause fuel supply problems make sure yours is working correctly.
 
I would check the water temp on the engine gauge first, when it shuts down it sounds to me like it is going to project mode as it is being starved for cooling water. I would check the sea-strainers first.
 
IMG_4230.JPG
As an aside, if you are running that motor at 4200 rpms for 40 minutes at a time, its shutting down will be the least of your problems. Especially if you do that cold as you mentioned in your post. It will soon be toast.
 
My experience with these symptoms points to deteriorating fuel lines. Air would start to get into the system after warm up and would be very boggy and sluggish to no response on throttle.
 

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