Engine Problem?

[G-Daddy]

Here are the details: Boat is a 1998 Sportcraft 252. Engine is a Mercruiser 350 MAG MPI. Serial Number is OL003715. Straight inboard with a Velvet Drive transmission. Boat was used in July/August on Lake Ontario and ran well when we put her back on the trailer and brought her home. Next time she was dunked was day after Thanksgiving on the Chesapeake. Going out of Crisfield to the Bay, we could only get her up to 2500 RPM and she would bog. Did some testing on the fuel system like checking fuel filter - clear fuel with no water or junk. Sprayed some gum cleaner in the spark arrestor at speed and it really bogged down the engine. Tried a remote fuel tank and same results as off our built in tanks. During the testing the condition gradually worsened and at the end we could only get up to 2200 RPM. Took the boat to a Mercruiser dealer and they tested it and said they believe it is a water problem - probably leaking from the exhaust manifold/elbow joint.

Their recommendation is to pull the enigine and run it on a test stand to fully diagnose the issue. Also suggested it might be time to replace the engine. When we bought the boat it was supposed to have a new engine that only had 500 hrs on it. Evidence indicates that if a replacement was done that it was a short block - not an entire engine replacemnt. We have put about 200 hours on her in the two years we have run her.

Cost estimates are $3500 - $4000 to pull the engine, test it, replace manifolds and elbows and reinstall the engine. Of course any othe rproblems they uncover would involve additional cost. Alternate is to replace the engine with a drop in full factory replacement engine. The new engine would be like the old engine except dry exhaust joints and a fuel cooler up on the engine rather than below it. Cost for replacement is around $9600.

Thoughts?

 

[LorenHaus]

Re: Engine Problem?

A few things to do BEFORE pulling the engine out to diagnose internals:

1.) I would start by pulling all the spark plugs out, and lay them out in accordance with how they came out of the block. Look for plugs that are burning ligher than the rest or are wet but do not smell like gas. That would be an indication of water intrusion.

2.) Do a FUEL PRESSURE check. MPI's dont like to run well without proper fuel pressure. This is an easy one to do. Run the engine up to the range where it starts to bog and see if the fuel pressure is consistent or if it is dropping off.

3.) Look at the cap/rotor for signs of corrosion. Poor sparky means poor runny.

4.) Do a quick compression check. Verify you dont have a blown head gasket. If it was a valve hanging up/bent chances are you'd hear it banging away inside when running.

5.) Pull the exhaust elbows off. Check to see if the exhaust port in the manifolds shows signs of water entering the block from the exhaust elbow gasket. While you have the elbows off, look down in your exhaust Y pipe and make sure your water shutters (basically a check valve) are still in good shape. They arent designed to be a water tight seal, but they do stop water from shooting back up into the engine when you shut the engine off in the lake.

 

[Don S]

Re: Engine Problem?

Took the boat to a Mercruiser dealer and they tested it and said they believe it is a water problem - probably leaking from the exhaust manifold/elbow joint.

Their recommendation is to pull the enigine and run it on a test stand to fully diagnose the issue. Also suggested it might be time to replace the engine.

Find a new dealer.
The engine doesn't have to come out to test that sort of thing. Simply removing the exhaust risers and inspecting the joint will tell the story.
Even if that joint was leaking, it wouldn't affect the running of the engine. It would cause water in a back cylinder after you shut the engine off and the engine would hydrolock. Or did that happen?

Did they check the fuel pressure and do things like compression tests, checking the timing, hooking it up to a diagnostic computer.
None of that calls for the engine to be pulled and put on a test stand.

 

[littlebookworm]

Re: Engine Problem?

Definitely listen to Don. Get your boat to a different mechanic, one who knows how to diagnose and repair, not one who only knows how to replace and charge. It is extremely rare ( as in almost never) that an engine has to be removed to test it or diagnose its problems. A real marine mechanic would do a compression test, leakdown test, a fuel system and an ignition system tests. None of these require removing an engine. Furthermore, if I remember correctly, the engine is computer-controlled. A diagnostic computor will give a great deal of information. Take your boat and run! Hy