25 HP Merc compression

[Hugeman]

I was having some problems with my Starter not working on my 1999 25 HP merc. <br />( serial # 06765886)<br />I had the starter rebuilt last year by a local outboard shop. I towed my boat in today after storing it all winter and asked them to fix the starter again. I had used the motor only a about 6 times last year and the starter quit after one day of use. The motor ran well with lots of power but I had to pull start it. The last time I used it the elec starter did not work at all so we had to pull start again. It had trouble starting this day but ran fine after getting it going. The boat was then stored for the winter.<br />THe shop told me that the first thing they do is A compression test and that one cylinder was around 80 psi. The other was ok. They also told me the Armeture? had to be replace on the starter.<br />SO he told me the piston was scored and needed to be replaced and if you do one the cost was minimal to do the second one. Cost with shop time (8 hours)was around $1000.00 can.<br />I told them to not do the repair.<br />I was reading the manual that says after storage the motor should be warmed up before compression testing due to relaxing of the rings. It does not sound like they did this? Would or could the piston be scored or how would he know unless you pull the head and see??<br />I bought the motor and boat last year form a sick elderly man who only used the motor one season. He was a fastidious person with his boat as I am. Carefull oil mixing. How oculd such a new motor have a scored piston?<br /><br />HELP!!<br />ANy opinions?<br />Hugh

 

[Hooty]

Re: 25 HP Merc compression

Lots of options here. The first is to check the compression yourself but you can't do that without a starter so that means we gotta fix the starter. Is the armature bad? Well, we gotta find that out or just replace the starter. I'd take the starter to a starter/generator shop and let them look it over. If the compression is low, there are some other things to be looked at before doing anything major. <br />'kay, so get the engine back, take the starter off and take it to the starter shop and see if they can fix it, then get back on this same thread here and lettus know what's going on.<br /><br />c/6<br />Hooty

 

[andrewkafp]

Re: 25 HP Merc compression

i reckon it would be rare for a 5 yo motor to have bad compression (Unless cooked) <br />I would check it myself.

 

[JB]

Re: 25 HP Merc compression

Your starter was probably not bad the first time, Hugeman, and it probably isn't bad this time either.<br /><br />Nine out of ten times that a starter doesn't work the trouble is simply bad cable connections or bad cables. Once out of 20 times the trouble is the solenoid, the neutral start switch or the starter switch.<br /><br />Once out of 20 it might be the starter. Electric starter motors are just about as tough as a crowbar. Replace the brushes and resurface the commutators every ten years or so and they will last forever.<br /><br />Go to the "Outboard wont start" article in the FAQ section and follow the steps for troubleshooting a starter circuit.<br /><br />The compression question is another story. I will leave you in the capable hands of the Merc-sperts on that one.<br /><br />Good luck.

 

[rickdb1boat]

Re: 25 HP Merc compression

I think you could get a decent compression reading by pull starting it with the plugs out. Or, at least find out if they are close to the same reading on each cylinder. Others do it that do not have electric start. It will pull over pretty easy with both plugs out, even though you will have one cylinder with the compression tester in it. Don't forget to ground the plug wires when you do test it..<br /><br />Also, jump directly from the battery to the starter wire(Big One) with heavy jumper cables and that will tell the story about loose or corroded cables or a bad starter. Either it will turn over or it won't. Go from there...

 

[Hugeman]

Re: 25 HP Merc compression

I checked the starter last year and had 12 volts to the starter. The cables were fine and the solinoid was good.<br />I have a starter cord to pull start so I guess I could check the compression with 4 or 5 pulls?<br />I had alarm bells going off when he told me the piston was scored.... and i was thinking how do you know by just a compression check?? I have read about the de-carbing and will try that after I go out and get a compression guage. Funny thing is I need a compression gauge for my diesel truck which is different than a gasoline one. ($100.00 more)<br />When I got this motor last year it did not even have a paint chip or scratch on it. The motor was virtually new.

 

[rickdb1boat]

Re: 25 HP Merc compression

Edited my post above. Check it out...

 

[JB]

Re: 25 HP Merc compression

Amend Rick's advice on the jumper cables. You must also connect the battery ground cable directly to the starter case. Connection failures most commonly occur in the ground circuit, so reading 12v at the starter does not eliminate bad grounding.

 

[Hugeman]

Re: 25 HP Merc compression

Thanks guys. I'll be looking at doing the compression check this weekend and re-checking the starter and grounds.<br />Ice is off a few of the lakes and I am itching to get out.

 

[rickdb1boat]

Re: 25 HP Merc compression

Good catch, JB.