350 mercruiser slow crank ... Hydrolock?

[Jason 641]

I just bought this boat, it has a 350 chevy mercruiser. the first time I cranked it when I bought it, it started right up, no problem. I ran it for a minute or 2 to look it over (with muffs on the outdrive) then shut it down, still everything seems fine. a couple hours later I tried to start it and the starter will barely turn over the engine, maybe a 1/4 rotation at a time, if that. I figured it might be the battery so I charged it up and tried again, same thing. I then pulled the starter off and turned the key to check it, the starter turns no problem.

Next I pulled the plugs out of the engine and turned it over, the engine spins great with the power of the starter, seems nice and smooth. No water came out of the cylinders when I was cranking it with the plugs out. so I put all the plugs back in and try to crank it. it turned over a couple times, very slowly, then went right back to barely turning like it is locked up.

Does anyone know what the problem is? or have any suggestions on what to look at next? I don't want to pull apart anything I don't have to since everything is a pain to get to.

Thanks,
Jason

 

[Fishermark]

Re: 350 mercruiser slow crank ... Hydrolock?

Welcome aboard!

The bushings could be shot on the starter causing a bind when under a load.

I would also suggest doing a compression check.

Have the battery checked out as well. It may be on its last legs.

 

[Haut Medoc]

Re: 350 mercruiser slow crank ... Hydrolock?

Welcome to iboats....
Since you did not see water, I would look at the starter itself (have it load tested at a starter shop)......
Check the battery condition, (load test)
Finally, clean all electrical connections that relate to the starting system.....
One other thing: Feel the primary starting system wires after you try to crank the engine.....
Warm/hot wires mean internal corrosion & should be replaced......
The cable ends can look good, but.......​

 

[Jason 641]

Re: 350 mercruiser slow crank ... Hydrolock?

Thanks for the quick reply's.

Wires definately get HOT. It looks like they have been doing that for a while now. The rubber insulation near the terminals is melted. The old owner actually put on a 2nd ground wire from the battery to the block and used a 0guage positive wire to the starter, thinking that was the problem.

I have tried 2 different good batteries with the same results, so hopefully it is the starter just not handling the load with compression in the engine. I'll pull the starter back off and have it load tested.

 

[chiefalen]

Re: 350 mercruiser slow crank ... Hydrolock?

Do the compression check, please post the result.

But sounds to me a new starter is in your future, marine please, don't want to read about a explosion.

The neg ground is it clean and the connections on the starter clean, all the connections clean.

You can try that before you shell out for a starter.

 

[oops!]

Re: 350 mercruiser slow crank ... Hydrolock?

hi jason....welcome to i boats....

this place has some of the best tech people ive ever seen.

they have literally saved me huge money.

when the mechanics i was paying for were all guessing.....these guys gave me things to check....

if you follow there instructions to a "t"..in the order they say...your problem will be solved, and you will be a happy boater.

im not a mechanic....but i had that problem too....it was the starter....so i can only GUESS...that would be a place to look

cheers
oops

 

[FreeBeeTony]

Re: 350 mercruiser slow crank ... Hydrolock?

I would measure the voltage at the starter with respect to the bolck with a DVM while trying to crank.........if it drops significantly and your battery voltage is good, you should check your connections.

 

[Jason 641]

Re: 350 mercruiser slow crank ... Hydrolock?

Thanks. All the terminals are good and clean and I have good voltage. I just remembered that I did see a bit of smoke from where the wires were getting hot when I was cranking it with no plugs in, so the problem probably is the starter.

I will do a compression check when I get home this afternoon before I get a new starter. Does anyone know of a good source? I know a buddy of mine just got one here locally but if anyone can suggest a good place to order one from I would appreciate it.

 

[Don S]

Re: 350 mercruiser slow crank ... Hydrolock?

I just remembered that I did see a bit of smoke from where the wires were getting hot when I was cranking it with no plugs in, so the problem probably is the starter.

IF the cable is smoking, it could be just a bad cable. If it's smoking where the terminal crimps on the cable, it probably is loose and corroded at the connection of the terminal on the wire.

I will do a compression check when I get home this afternoon before I get a new starter.

You can't do a compression test if the starter won't crank it at the proper speed.

 

[Jason 641]

Re: 350 mercruiser slow crank ... Hydrolock?

I just did a compression test .. without the spark plugs in the starter turns the engine good enough to get some readings. The only thing is, I did the compression test on a cold engine since I can not get it to start. Anyway, here are the results ...

#1 = 160
#2 = 155
#3 = 160
#4 = 150
#5 = 110
#6 = 150
#7 = 160
#8 = 150

The #5 is low, but there wasn't any water in the cylinder.

 

[Jason 641]

Re: 350 mercruiser slow crank ... Hydrolock?

I just pulled the starter again and took it apart. it was pretty nasty inside so I sprayed it all out and cleaned it up. Put it back in the boat and it started up. it is still having a bit of trouble starting the engine but it does work. So I am going to order a new starter and I will keep this old one around as a spare.

Thanks for all the help.

Jason

 

[Don S]

Re: 350 mercruiser slow crank ... Hydrolock?

So I am going to order a new starter and I will keep this old one around as a spare.

Take it to a starter shop and get it fixed if you want to keep it as a spare. Just setting around on a shelf will cause it to fail a second time for you.

 

[Jason 641]

Re: 350 mercruiser slow crank ... Hydrolock?

Does anyone know what starter part # I should be ordering? I have found a couple different part #s for that year. The boat is a 1985 Mach 1. Do I need a S/N off the engine to find out?

 

[Don S]

Re: 350 mercruiser slow crank ... Hydrolock?

Do I need a S/N off the engine to find out?

That would be the best way.

 

[Bondo]

Re: 350 mercruiser slow crank ... Hydrolock?

Do I need a S/N off the engine to find out?

Ayuh,...

That's how they're listed on this page.....

 

[Jason 641]

Re: 350 mercruiser slow crank ... Hydrolock?

Thanks for the help.

 

[hrznjb]

Re: UPDATED 350 mercruiser slow crank ... Hydrolock?

Re: UPDATED 350 mercruiser slow crank ... Hydrolock?

Jason,

Any resolution to this issue? I have the same engin and same problem. I have blown through two starters (the reduction gears) trying to address it by replacing starters.

I think that the issue is more fundamental ... like a hydrolock or power robbing problem causing the engine to be more difficult to turn.

Interested in your results.

UPDATED
It was hydrolocked. Seems like the obvious answer in retrospect.