mercruiser 898 ignition

[jpaulw]

I have mercruiser 898 IO which is low hour refurb and has been running not problem. This is the 305 V8, and as far as I know is stock. I got it really wet a couple of weeks ago (yes, folks, I put the boat in water minus drain plug.) Cooked the alt but replaced the same day and is working now. Problem is that I cannot turn off ignition from the ignition switch. When I turn key to off postion, the accessories go off, but not the run circuit. I have had to use the cut-out switch on the shift cable under the engine cover to kill the engine. Ignition switch seems ok. Any idea what I've done? Help?

 

[petryshyn]

Re: mercruiser 898 ignition

Is it possible that the alternator is feeding back to the ignition circuit? Try running engine with all the wires disconnected from the alternator. If engine shuts off normally, then thats where to start(alternator circuit) <br />Some applicatiions use a diode to prevent this. Maybe yours is shorted

 

[jpaulw]

Re: mercruiser 898 ignition

Thanks for the tip, Schematic. I will try it. Any other ideas, just jump right in.

 

[ODDD1]

Re: mercruiser 898 ignition

A starter slave solenoid full of water will cause this, too.

 

[jpaulw]

Re: mercruiser 898 ignition

Thanks, ODDD1. The solenoid full of water sounds like a real possiblity. Would this drain and dry out eventually, or do you think water will stay trapped. Or even worse, would solenoid be permanently shorted? Do you know any way I can check this out before removing solenoid to dry it out? Any reasonable test or tests you can suggest to isolate the problem? I am semi-ignorant, but willing to work on it. Thanks.

 

[petryshyn]

Re: mercruiser 898 ignition

While the engine is running, turn the key off. If the engine doesn't quit, disconnect the small wires from the slave solenoid. If the engine quits, then ODDD1 has nailed it!!

 

[jpaulw]

Re: mercruiser 898 ignition

Thanks guys. I have a question, though. I got home too late to work on the boat, but checked my Seloc Mercruiser manual. It shows two versions of the 898. One wiring diagram has the slave solenoid and the other shows starter solenoid mounted on starter. I have to go check this out on the boat. Will the test Schematic suggests work if there is not a separate solenoid? Thanks again.

 

[petryshyn]

Re: mercruiser 898 ignition

if this is a point type ignition with a bypass resistor.....yes. Otherwise, not likely....

 

[jpaulw]

Re: mercruiser 898 ignition

I checked the system a little more. It does have a slave solenoid; two leads to starter, one lead to ground, and one to harness which I am assuming is ignition. The distributor is Mallory tagged "electronic ignition" and has no points. Wiring is direct from coil to distributor (not through the box shown on my "Thunderbolt" system diagram.) I will be on it this weekend, thanks to your helpful suggestions.

 

[ODDD1]

Re: mercruiser 898 ignition

jpaulw..you will have a solenoid mounted on the starter...there is an additional solenoid [slave] mounted at the rear of the starboard exhaust manifold [if you have log style rear exit manifolds] or mounted at the front of the starboard maifold if you have center riser exhaust manifolds.....when I replied I assumed you had log style manifolds and the older style slave solenoid...they were more prone to this problem....

 

[Walter]

Re: mercruiser 898 ignition

There's another issue here also...<br /><br />You've probably introduced water into your u-joint bellows via the vent hole. Chances are pretty good you'll experience u-joint failure in the near future. You can help avoid that by pulling your outdrive ASAP and inspecting/lubing your u-joints.<br /><br />Been there...done that!<br /><br />Walt

 

[jpaulw]

Re: mercruiser 898 ignition

ODDD1, you are correct in the assumption that it is the log style manifold setup, with the slave solenoid mounted rear starboard. Schematic suggests this test; start engine; turn off key and if engine does not shut down, then pull "small wires" from solenoid; if engine turns off, the solenoid is the culprit. I am assuming the "small wires" would be the ground and the yellow-to-harness which are indeed smaller gauge wire than the leads to starter. I am guessing that the solution is a new slave solenoid, since these are supposed to be sealed units, right?

 

[jpaulw]

Re: mercruiser 898 ignition

Walter, thanks for the heads up on the u-joint situation. I would never have thought of that. I have always taken the boat in for anything requiring removal of outdrive. I wonder if there is a way to do this safely on my on? I just worry about handling the weight without damaging me or the boat. Or is this trickier mechanically than I think? Thanks again.

 

[petryshyn]

Re: mercruiser 898 ignition

jpaulw <br />Don't forget about removing all wires from alternator and trying with wires disconnected.(do not disconnect while running, remove them before starting).

 

[ODDD1]

Re: mercruiser 898 ignition

Jpaul, scematic is correct on the test...I think you should have an internally grounded slave solenoid with a small yellow wire and a small purple/yell stripe [which is the one we are worried about]....let me know what you got, I may be cornfused on this, have been in a few boats this week.....

 

[jpaulw]

Re: mercruiser 898 ignition

Thanks, Schematic. I will try the alt test first. This is easy, because there are only two wires on the alt; a ground and the hot lead. <br />And ODDD1, I will have to wait for the weekend for time to work on the dang thing, but I will check again on the solenoid wiring. The colors may not be right, though, since this engine was installed after an old four cylinder was removed (about four years ago). I don't know that all the wire colors are kosher, but the wiring has not been a problem. Just need some daylight hours. Thanks again, guys.

 

[petryshyn]

Re: mercruiser 898 ignition

bad news jp<br />If you are "sure" there is only 2 wires (batt and grd) then don't bother with the test. The feed back issue only applies to ignition excited alternators.<br /><br />Sounds like you are going to have to trace the ignition circuit all the way to the distributor.

 

[jpaulw]

Re: mercruiser 898 ignition

I am sure about the two wires to alt. I am on my way home right now to do what I can before dark. If the other checks reveal nothing, I may be back for help in tracing that circuit. I have a book, but I also have an old, much worked on boat. Thanks Schematic, all you guys have been great. If I can find it soon I will fix. Otherwise, I am going to go for help on the water in the ujoints problem. That sounds scary and likely to get worse.

 

[jpaulw]

Re: mercruiser 898 ignition

Ok, removing the two smaller wires on the slave solenoid has no effect. Something is wrong, though, because both test as grounded. One runs to terminal block ground, I can't see where the other runs to, but it tests continuous to ground on a voltmeter, whether the engine is running or not. Both heavy wires run to starter solenoid, and one is always hot, the other I assume will be hot when the key is turned to start position, but is not hot with engine running. Thanks again guys. I am taking it in to pull drive. I'll ask them. If they can't find it cheaply, I'll just start again. I think I really need a systematic plan to positively eliminate each element from the key on back. Is that the way it's done? I'll keep looking here to see if anything new pops up.