Mystery Engine Problems

G

GrecRI

Member
Member
Joined
Apr 21, 2006
RO Number
20962
Messages
248
I have a 1985 26' SeaRay with 2010 5.7L 350 Vortec and an Alpha 1 drive. Everything had run flawlessly since this engine was installed at the beginning of the 2010 season. Until yesterday. Two problems that may or may not be related.

Yesterday: Engine started fine but when I put it in forward to leave the slip, the engine stalled. Restarted fine, put it in forward, and stalled again. Reverse was no problem, but forward made it stall. After about the 5th try it seemed fine.

After that, it ran fine idling out of the cove but when I went to bring it up on a plane it reached 2800 RPM and dropped out to 0 RPM like someone had turned the ignition off. Then it dieseled a bit and started to take off again. I brought the throttle back and it ran fine at lower RPMs but every time it hit 2800 the problem would repeat. A friend at the marina told me that he had a similar problem that turned out to be water in the gas. Didn't make sense to me but I put some Startron in and went back out. After a couple of hesitations it seemed like the whole problem disappeared. Never stalled once. I thought it was resolved, but it may have been a coincidence.

Today: When I put it in forward to leave the slip today, I had the same stalling in forward issue. Reverse, no problem but in forward it stalled. After 5 - 6 tries, the problem disappeared. Ran smooth leaving the cove so I started to bring it up on a plane. This time, at 2200 RPM it dropped out. Same symptoms. Shuts right down then diesels for a few seconds as I bring the throttle back and then begins to idle smoothly like nothing was wrong. After the first two times at 2200 it also began to do it at lower RPMS - as low as 1100. If I raise the RPM up in neutral there doesn't appear to be a problem. I brought it to 3000 in neutral and it still was running smooth. I added more Startron just to see, but it didn't make any difference this time.

I'm lost. All feedback would be appreciated.

Thanks in advance.
 
Did you replace your entire MerCruiser powerplant (engine AND outdrive) or only the engine? If you changed only the engine, what is the condition of the Shift Cables (particularly the "lower" shift cable, the one from the Shift Plate down through the Transom to the Lower Unit)? If the Lower Shift Cable is sticking, it'll operate the Shift Interrupt Switch and kill the Ignition when you try to shift. This should happen ONLY when the boat is in the water with a propeller installed AND you are coming OUT of gear. But if the cables are sticky, or incorrectly adjusted, it'll cut ignition at other times. As another hint, a new lower shift cable will stretch a little in the first few engine hours of use, requiring adjustment.
Shift cable and adjustment won't cause it to diesel and the other issues you mention.
 
It's just electrical....just so's you know it ain't the engine.

Things to check...
Shift interrupt switch.
Neutral safety switch.
Any electrical connection within the ignition circuit....coil, distributor, ignition switch.
 
Even maybe the (safety lanyard) Kill Switch...
 
If you had water in your fuel, that water would still be in the filter. I would replace it and put the contents in a clear container so you can see if there was any water.
 
May need adjustment on the shifter cables. There is a safety drive switch on the cables rack by the engine.
 
I also agree with Ray's comment about Cap and Rotor. In ours, it'd miss coming up on plane, possibly be OK at cruise, but sometimes backfire. Seemed better warmed up. I changed Plugs, Wires, Cap, and Rotor. From the way the Cap and Rotor looked, dirty with corrosion flakes inside and corrosion on contacts, my guess would be that the Cap and Rotor alone would have solved the problem. Still, check Shift Cables, Shift Interrupt Switch, other Switches.
 
Carb Sandy. 4 brl Holley.

When i first got to the boat yesterday, I noticed a belt was loose, so spent an hour finding a suitable leverage point to tighten it.

Then checked for connection issues with coil, distributor, interrupt switch, etc. Came up dry. I'm a bit over my head as far as checking the proper function of the coil, so if it goes that direction, I will probably get a mechanic down there.

Discovered that my kill switch (lanyard switch) on the mercruiser shift control (MPC 4000 series) is not working. The engine continues to run regardless of switch position. Also the throttle only button seems a little sticky. So, I'm going to pull that unit off and check whatever electrical I can with its' wiring diagram at hand.
 
Check the interrupt switch action again with someone doing the shifting as you watch the action. The interrupt shift plate is an elongated triangle that mounts to the plate that the remote and lower cables connect to. The shift plate has a 'U' in the wide end that the roller of the switch sits in. This roller has to be in the bottom of the 'U' for the engine to run. Slightly out of the bottom will cause interrupted running. This is usually caused by a sticky lower shift cable. Unfortunately, it's not uncommon for this cable to stick or even fray because of the contortions it has to make to go to the outdrive.

The connection to the switch need periodic cleaning as it 'interrupts' the ignition circuit to the coil.

Another thing to check is the capacitor in the distributor. They used to cost a buck but I expect they're over $5 now.
 
Tensioning non-serpentine belts by moving the hinged alternator can be difficult so say the least. I usually carefully use an approx. 2+'long pry bar against neighboring parts, but I think a threaded rod of appropriate length with a turnbuckle frame on one or both ends as spreader device may greatly simplify tensioning before re-tightening the alternator slotted bracket fastener. Barring the latter , I suggest loosening but keeping a lot of friction on the slotted bracket fastener so the belt tends to stay tight as you re-tighten the bolt.

My blue engine mfgrspecs no more than 3/8" deflection I believe , but you should not be able to turn the alternator pulley by hand.
However , too tight and you may well prematurely damage RW & circ. water pumps or alternator bushing bearings and /or seals, perhaps power steering too.

If you have serpentine belt and tensioning is not happening automaticallyyou may need to calen , lube and exercise the idle/tensioner that has "frozen" to an inadequate limit of range.
 
quote:
Originally posted by boatcomfort

May need adjustment on the shifter cables. There is a safety drive switch on the cables rack by the engine.

Click to expand...


start with the safety switch. disable it and see if the problem goes away.
 
As described by J-D and Charley above, there was a problem with the lower shift cable, which was affecting the interrupt switch. If you adjusted it to 6", shifted once, and measured it again, it would measure 6.5". After shifting again, it would measure around 6.25". Each time you put the boat in gear, the measurement would change significantly enough to affect the interrupt switch. The boat was hauled and lower shift cable was changed.

The stalling when shifting problem was resolved. We took it out for a ride and had no problems at any speed. So as of today, it appears that both problems have been resolved. I'm not clear on how the bad shift cable could have triggered the interrupt switch once we were underway, but we haven't been able to recreate the problem.

I'll post again if the problem reoccurs.

Thanks for all the input guys.
 
You must log in or register to reply here.
Back
Top