'75 - 25HP Won't Start - Low Compression?

[Jmcever]

Just joined the forum - lots of good info here. <br /><br />Bought a "new to me boat" just before the holiday's. Previous owner said it would start but sputtered - would only run at half speed. After many tries and reading through some previous postings I got it started one time by squirting some fuel mixture down the throat of the carb. It seemed to run okay. I shut it down and haven't been able to get it started since. Here is what I know so far:<br />- Spark looks okay<br />- Checked point gap (.020)<br />- Carb looks to be okay - took it off - looks like it has been rebuilt recently. No debris.<br />- Compression is low - 65 to 70 psi in both cylinders. My compression gauge is old - has rubber boot that you press against engine - I will recheck with a differnt gauge before proceeding.<br /><br />My plan (when the parts store is open):<br />- buy manual<br />- retest compression<br />- install new points & condenser<br />- rebuild carb<br /><br />If compression is truly low - What am I looking at having to do? Is there anything else I need to check before I get started?<br /><br />Thanks in Advance,<br />Jim

 

[tashasdaddy]

Re: '75 - 25HP Won't Start - Low Compression?

welcome, first model # as much info as you can give so we know exactly which engine you have. your on the right track with a manual, don't buy clymers, you can order one from iboats or kencook.com or marine something. listen to the guys here and get a free education that worth millions, when it quits and there is nothing but water around you.

 

[Jmcever]

Re: '75 - 25HP Won't Start - Low Compression?

Model is 25502B (1975 25 HP Evinrude). Just re-checked the compression. With a good hard pull I get 70 psi in one and 90 psi in the other.<br /><br />PS - Huskys are beautiful animals but I prefer Goldens.

 

[Jmcever]

Re: '75 - 25HP Won't Start - Low Compression?

Another symptom? The one time I had the engine running (about one minute), I had it in a trash can filled with water. I just dumped out the water and there seems to be a lot oil in it. There is also black oil coming out of the exhaust and out two small weep holes in the lower unit. I drained the fluid in the lower unit and it looks okay (greenish color, not milky). I’m beginning to think I’m in for some major refurbishment!

 

[steelespike]

Re: '75 - 25HP Won't Start - Low Compression?

Not to worry.That sludge is pretty normal exhaust residue especially when running in a can.100 lbs compression is considered ideal minimum but motor will run with less.It is important that it is within 10% between cylinders.A good decarb treatment my help loosen up any stuck rings.Be sure the throttle and choke are open when checking compression.With luck you might get it close to the magic number.

 

[tashasdaddy]

Re: '75 - 25HP Won't Start - Low Compression?

got new manual from santa, it's published by the same people who publish the clymer crap, does not have the compression rating for this, points are set right, plugs should be chanpion j4j set at .030,

 

[JB]

Re: '75 - 25HP Won't Start - Low Compression?

I like Steelspike's suggestion.<br /><br />Your compression is out of spec in that the cylinders are not within 15%, but neither is trashed. . . .just a bit lower than some guys expect. That suggests to me that you have carbon sticking up the rings.<br /><br />After the carburetor rebuild and fresh diaphram in the fuel pump do a thorough decarb before you start tearing anything else down. I would say the odds are good that your compression will even up at around 90 psi, which is satisfactory for the 25hp.<br /><br />If you have a hot, 7/16", blue spark from both, I wouldn't mess with the magnetos.<br /><br />Good luck.

 

[tashasdaddy]

Re: '75 - 25HP Won't Start - Low Compression?

now you are hearing from a few of the ones that will educate you. they have all my respect.

 

[Jmcever]

Re: '75 - 25HP Won't Start - Low Compression?

Thanks for all the input. I checked the compression with throttle and choke wide open ... same results (70 / 90 psi). I'll check the spark (7/16") in the morning when my son is here .. I can't convince my wife to hold that wire.<br /><br />I'll let you know how things go.<br /><br />Thanks again,<br />JMc24

 

[Jmcever]

Re: '75 - 25HP Won't Start - Low Compression?

Okay - I couldn't wait. Good news. I have good spark on #1 (greater than 7-16") but none on #2 (Although I can see it jump across the gap of a spark plug). I swapped the wires leading to the coils and then I get a good spark on #2 and none on #1. This should rule out the coils ... hoping I've got a bad condenser.<br /><br />JMc24

 

[Solittle]

Re: '75 - 25HP Won't Start - Low Compression?

Your plan from your first post is solid coupled with steelspike's suggestion on a decarb. If your compression readings does not get closer together you will need to pull the head for a look see.

 

[Chinewalker]

Re: '75 - 25HP Won't Start - Low Compression?

The lack of spark could explain some of the unburnt fuel/oil in the bucket, too, as one cylinder's fuel charge would be cycled through unburnt. Once you clear up the spark issue you'll likely see a lot less unburnt fuel....<br /><br />- Scott

 

[andy6374]

Re: '75 - 25HP Won't Start - Low Compression?

Plus, the lack of spark and unburnt fuel and oil would lead to lots of carbon build up in that cylinder. Get the spark back and do a decarb.

 

[Jmcever]

Re: '75 - 25HP Won't Start - Low Compression?

Thanks for all the great input -- I think I'm getting closer. #1 spark is good. When I hold the rubber boot on number two I get shocked and have a weak spark. If I run the #2 lead through the #1 coil I get a good spark. <br /><br />Is there an easy way to test the number 2 coil or do I just go buy a new one. Local boat parts place was closed today .. hope they open tomorrow.<br /><br />Thanks again,<br />JMc24

 

[BoatBuoy]

Re: '75 - 25HP Won't Start - Low Compression?

Save yourself (and your wife) some grief. I made this spark tester with junk around the garage. Adjust the gap to what you want, clip to a good ground and attach plug wires to studs. Crank and observe spark. Credit goes to SoLittle for the idea.<br />

 

[tashasdaddy]

Re: '75 - 25HP Won't Start - Low Compression?

check i boats prices first. it might be worth waiting 3 days. boat bouy and so little great idea.

 

[Solittle]

Re: '75 - 25HP Won't Start - Low Compression?

BoatBouy - Nice job with the spark tesator. It looks a heck of a lot better than the one I made.