GT40 Issues after shop service.

1997 SN 196 GT40

Long standing symptom/problem prier to and reason for servicing engine last week:

Running warm up to 190 at idle after a few slalom passes. But in the pass would go down to 170s. Then climbing back to 190-5 after dropping skier and lining up for another pass. Back down during pass. Been like that for a while. Did all the usual; new thermostat and gasket, checked all hoses, checked trans cooler, checked all ports in thermostat housing, checked intake under hull and so on. All good. Conclusion; flow problem due to old manifolds (1100hrs). Plus old hull huger muffler was going bad..developed a crack.

Other than temp issues and some needed maintenance, the boat ran smooth as butter. Strong, responsive and sounded normal.

Sent to shop week ago and the following was done. The shop replaced manifolds and risers, plus some items added to the job for general maintenance. Specifics;

1.     New Exhaust manifolds, risers, gaskets and ss fasteners (old ones were in fact bad.. I saw the inside of one of them)
2.     New Hull hugger muffler
3.     New exhaust hoses
4.     Replaced fuel filter-FCC filter
5.     Installed a new inline fuel filter. It did not have one before.
6.     New thermostat/gasket
7.     Oil change and filter
8.     Transmission fluid changed
9.     New cap and rotor
10.     Cleaned flame arrester
11.     Tank drained and 5 gal of fresh mid grade added. Shop chose to do this but gas in tank was not more then 2 weeks old and had full can of Seafoam added
12.     Clean and grease rudder and rudder port
13.     Shaft packing
14.     Bilge cleaned

Received boat back. Started and idled normal. Backed off of trailer. Short 100yrd run to dock done at idle speed; felt and sounded normal. Parked boat. Few hours later did a test ride. Seemed ok at first. Seemed to run as normal throughout power range and idle. But within a few minutes, idle started stuttering. The range between 1000-2000 as throttle was pushed up, it stuttered and struggled a great deal. Continue pushing throttle and at 2500rpms, it gave a mostly normal response on up to WOT. Some slight stutters detected but barely noticeable compared to the 1000-2000 range. Back down to 1200 still in gear, the boat started surging between 1500 and 2000. Up and down, up and down. Continued this until the throttle was repositioned. Idle still stuttering. Left boat sit for a couple hours, then second test ride. Seemed to run slightly better this time out but was repeating all of the same above symptoms after running for a bit.

Day 2, added 10 more gal of mid grade gas and test ride results were exactly same. Cold it ran well until reaching normal temp. Then same poor results.

At PCM’s suggestion, the following has been attempted or found to be normal when checked. After some but not all, a test ride was done with the exact same symptoms as above..no better, no worse.

1.     Removed new in line fuel filter, as it was not part of the system before. (test ride..no change)
2.     Both HP and LP pumps prime as normal with key turn. Aprox 3 seconds
3.     LP pump tested with normal flow/volume (20oz in 10 sec) and pressure. All connections appeared normal and were reseated. (test ride..no change)
4.     Fuel pressure gauge shows 35psi at idle and 41psi at WOT. No change during lake testing for both points. Also, fuel pressure held with key off @35psi.
5.     FCC opened and full of fuel to the top. No water. All connections appeared normal, reassembled and psi did show again as normal with gauge at idle and WOT. (test ride..no change)
6.     At idle removed vacuum hose from Fuel Pressure Reg on rail. PSI jumps to 41psi 830rpm when vacuum hose removed. Reattached hose and normal operations of psi at idle-35psi 730rpm and 41psi at WOT. (test ride..no change)

All symptoms have stayed exactly the same for every test ride. Over several days of lake testing it seems that the issue arises when boat is up to temperature (160). Seems there are no issue when runing from a cold start and running up through the power band. 100% normal operation. Smooth as butter. Once boat is at temp, the issues at idle (stuttering) and between 1000 and 2000rms (struggling, running rough, losing power) are present. At 2500rpms it catches and runs close to if not normal through WOT.

Thinking sensor problem… possibly temp sensor as it only runs poorly at temp. Or throttle position sensor as it runs the worst between 1000-2000rpms. But do not know how to test any of these. Not sure what other sensor it could be but the symptoms/problems are very very consistent. Cannot think of anything else it could be.

The boat ran fine before entering the shop and poorly after. The shop did not lake test boat before repairs and I’m confident they did not hose test it. Problem described to them was just running warm and a few maintenance items needed so perhaps no need to hose or lake test. I would have had them address poor running if it was running poorly prior. Especially this bad. Temp issue was solved. They contend that it must have been running poorly before their work. It could be a complete coincidence and a separate isolated incident. Or maybe its something/parameter that they changed that is causing the computer to not properly calculate fuel needs. But just guessing. Perhaps something was bumped. Truly appreciate any help.

I had a similar stuttering issue and was related to cross talk between the TFI-IV module and the distributor wires. It wasn't heat related so not sure but it was so intermittent that it was hard to diagnose. I bought an intermittent ignition analyzer and every time I plugged that thing in the boat ran great. Unplug it and the boat stuttered. I thought it was the connector to the TFI-IV module not properly connecting to the module. The analyzer has much heavier duty connectors and pins. It turned out that when I plugged in the analyzer I was pulling the wires away from the distributor and that is why it ran fine on the analyzer. After replacing the connector 2 times(one from Napa(it was china junk) and one from Ford OEM(thicker connectors)) I finally realized what was going on. This drove me nuts and it took a bit to figure out. The solution was to either put the bonnet back on the distributor to prevent cross talk and/or move the wires farther away from the distributor. I did both and put some of that liquid electrical tape on the wires to the TFI-IV to help prevent any cross talk. Something to look at and just suggestions to help. Maybe they shifted the wires around just enough to cause cross talk when replacing the distributor cap. Also take off the distributor cap, check the rotor and cap make sure everything is good, wiggle the PIP sensor and make sure it isn't loose. Look for pieces of loose metal on the PIP and blow them off with an air compressor if you see anything. Maybe some metal flakes fell off the old distributor and rotor when they replaced them. The PIP is magnetic so the flakes would hang on to it.

Hope any of this helps.

Brian,
Welcome to CCfan. Sorry to hear about your problems. They can frustrating especially for a mechanic. I'm sure we can give you some ideas.

Was it a CC dealer that worked on the boat? What was this in line fuel filter they installed and then removed?

How about some pictures as well as a diary entry?

With a distributor cap change, did you verify the plug wires are right?

Has the dealer tried a code reader to see if there is any stored codes ?

The new distributor cap could be bad maybe? It wouldn't be the first time.

If it was running rough from too lean fuel mixture, wouldn't the spark plugs show that?

Here is the one Mark (lewy2001) has recommended in the past,he was finding them on amazon so look there too. I think a extension cable was handy too if I remember right.

8122pbrainard wrote: 97MasterEdition wrote: All that they worked on was done well as far as I can tell. But, I'm still confused with the in line fuel filter they installed and then removed per PCM's recommendation. Again, what filter was it?

Pete, it was probably something like this. These are sometimes installed halfway along the line between the fuel tank and the motor. I get to mine by removing the floor panel behind the motor box. For me, it's the only filter I have, but they are sometimes installed in tandem with the Fuel Control Cell filter... and sometimes not from what I've read. It's actually odd for a Carb'd boat to have them, but it's how mine came.

If it wasn't there before, it would probably just add extra flow resistance. And of course, it's only meant to mount one way (there's an arrow for the direction of flow). But physically, it can be installed in either direction and hence gives an opportunity for human error. Maybe the shop was thinking they were adding extra protection by adding it in there:

Great minds think alike

That is what was installed and where it was installed (under floor board). I removed it a a check to see if that could be the cause. It was not. No difference in the way the motor acted without it in place. Will probably put it back. And I have seen photos of the same SN but a yr or two newer with that exact one already installed so it was something I believe CC started doing as standard equipment.