engine only sometimes cranks, forgot tagging in last thread

[rnapple]

I have twin 5.0L MPI Mercruisers with 305 small blocks. I know a little about mechanics having been through USCG MK school but I am ameture at best.

This problem sounds like one that was just discussed and people were talking about valves and alignment and whatnot. Well I didn't mess with any of that stuff. But I have been working with my electrical and I think that is the problem with the last guy with this similar problem. Well here it goes....

A lot of info here.
My stbd engine works fine but my port will crank when I first get to the boat. It won't start. I try to crank it again and it cranks less. On the third or fourth try the port engine acts as if it is frozen. In some cases the engine will crank forward a quarter turn then backwards a quarter turn. I just ran it the other day. I took the boat out and everything. The batteries are at 13.5 volts. the starter is new. I have been chasing this demon for weeks and spent too much money on everything. The positive battery cables are new but the grounds are not. I replaced the exhaust water shutters the other day and discovered that half of the inboard metal water shutter was missing. I suspect that it is in the Y pipe or stern drive but I don't know. It may have even gone up into the engine because some water did get into the engine when it ran slightly backwards the other day. I replaced the Starter Slave Solenoid. I had an electrician type friend come out the other and looked at it with me. we messed with the starter a little and low and behold it started and that was the day we took it out. Afterwards we tried to start it again that day. It wouldn't start and some sparks were seen coming from the starter. I have gotten a new starter since. Accidently Dropped the old one over board. Figures. I'm really thinking that there is a problem with the wires going to the starter. but I have no idea. Please Help!!!!

 

[Don S]

Re: engine only sometimes cranks, forgot tagging in last thread

I have twin 5.0L MPI Mercruisers with 305 small blocks

Need a serial number off the engine. Way too many different MPI setups to guess at.

my port will crank when I first get to the boat. It won't start. I try to crank it again and it cranks less.

What do you mean by cranks less? Slower, or cranks for a bit and stops.

I'm really thinking that there is a problem with the wires going to the starter. but I have no idea

Stick a camera in there and take a picture and post it.

 

[Silvertip]

Re: engine only sometimes cranks, forgot tagging in last thread

What do you mean the battery cables are new but the grounds are not. The engine end of the negative battery cable bolts to the engine block -- there is no "separate" ground. The engine end of the positive battery cable goes to the starter solenoid. So to replace either or both of those cables required reattachment so the connections were either shiny clean or they weren't. Intermittent starter operation, even with a new starter points to a bad solenoid, bad connections, or a weak battery. A battery that measures 13.5 volts may appear fully charged but you need to check that voltage while trying to start the engine. I'm betting you have a weak battery. If in doubt, charge it and then have it load tested. Or swap it with the other engine. If the problem goes away you need a new battery.

 

[WSKIPPER]

Re: engine only sometimes cranks, forgot tagging in last thread

Be sure it's not full of water and hydro-locked...removing plugs will tell you if that's the issue..good advise Silvertip...

 

[Speakrdude]

Re: engine only sometimes cranks, forgot tagging in last thread

Batteries usually will not show over 12.8-9 volts without the charger being hooked up and on, Are you reading voltage with the shore power attached? Problem sounds like battery with a dead cell. Simple swap batteries from the other engine and see.

 

[rnapple]

Re: engine only sometimes cranks, forgot tagging in last thread

You're right. The heads were full of water. I pumped water out and and let it sit over night to dry. I'm heading back today to put the plugs in and try to fire it up again and see what happens.

 

[rnapple]

Re: engine only sometimes cranks, forgot tagging in last thread

The reason the heads were full of water is cause the engine wasn't starting right before due to a faulty solenoid. This caused it to reverse a few times sucking water up through an exhaust with a faulty water shutter. Don't ever let people tell you those water shutters are pointless. They are there for a reason!

 

[Don S]

Re: engine only sometimes cranks, forgot tagging in last thread

You're right. The heads were full of water. I pumped water out and and let it sit over night to dry. I'm heading back today to put the plugs in and try to fire it up again and see what happens.

You mean to rust, not dry. You need to crank it over and blow as much water out as possible, then put the plugs in and start it, or try to. May have to pull the plugs a time or two and dry them off so they will fire. before it finally starts.