70 lb compression on mariner 150???

[lookingforluck]

I hit a sandbar and drove around on the lake in shallow water all day, (got out of channel) I thought that maybe my prop was bad because I hit something and needed replacing when I couldn't hardly get it to plane off and lost 14mph on top end. I thought that I would check the compression and it was 70 on all six cylinders. 1993 mariner 150 Two weeks before that I was running 68mph and would plane pretty quick??? Engine will only turn about 5100 rpm's WHAT HAPPENED?? Frustrated

 

[studlymandingo]

Re: 70 lb compression on mariner 150???

If your compression is only 70lbs. that is not very good. Since it is the same across all cylinders, I would check it with another compression gauge. It is very possible that the gauge could be faulty. You want a reading above 100 closer to 115-120.

Do a search on decarb. Follow those directions.

As to not planing; get a spark tester at your local auto parts store; make sure you are getting a good strong spark on all six.

Good luck and welcome to iboats!

Keep us posted as to your results.​

 

[lookingforluck]

Re: 70 lb compression on mariner 150???

I checked the checker and it read like 110 on my lawn mower so I don't think that it is the checker, also will carbonation cause the loss of power and loss of compression?

Thanks

 

[lookingforluck]

Re: 70 lb compression on mariner 150???

What are other things that could cause it to be low? How would you know if you had a bad head gasket?

Thanks

 

[NGABaldEagle]

Re: 70 lb compression on mariner 150???

Could be alot of things.
The same symptoms you will get when you have 10 gallons of water in the bilge. Did you check compression on each cylinder with all of the plugs out of the engine?

 

[lookingforluck]

Re: 70 lb compression on mariner 150???

Yes all of the plugs were out

 

[studlymandingo]

Re: 70 lb compression on mariner 150???

Carbon deposits can cause the rings to stick; but I wouldn't think all of the cylinders would be low like that.

Has your motor gotten hot or run out of oil? Maybe the reed plate is warped.

When you were running last week what was your WOT RPMs?

I have a 150 Mariner also; I have had your same experience on a couple of occasions. Twice I had trigger wires from the switchbox to the coil broken; once I had deliberately pulled a bunch of water into the bilge to give me some keel weight to cut through some nasty chop, I forgot to turn the pump back on before I took off the next time and I was carrying a LOT of water.

Check your spark and do the decarb​

 

[lookingforluck]

Re: 70 lb compression on mariner 150???

WOT rpm's were about 5000.....pitiful, I don't know what they were earlier in the year when the boat was running terrific because I just looked at the speedometer instead of rpm's. I don't know what the compression before was either because I didn't check it when I bought the boat. It does start good and run good, just no power. Last year the temp alarm did go off but I shut it down right then and have fixed the water pump this spring and it has done really well for two trips. The last two trips have been sad. 70lb bothers me a lot.

 

[lookingforluck]

Re: 70 lb compression on mariner 150???

bump

 

[tashasdaddy]

Re: 70 lb compression on mariner 150???

i don't know much about your engine, but if it were a johnny/rude, i'd say it ran hot, and blew some gaskets. clogged cooling channels and bad impeller from the sandbar.

 

[AMD Rules]

Re: 70 lb compression on mariner 150???

Was your battery weak during the test....spinning slowly? I'd borrow a second guage and charge your battery before digging deeper into it. Very uncommon for a motor to eat 6 pistons at once.

Any chance you overheated it (lack of cooling/ran out of oil)?

Can you see the condition of the pistons or cylinder wall through the spark plug hole using a small light?

Next step after that would be to pull at least one of the heads to take a closer look.

 

[lookingforluck]

Re: 70 lb compression on mariner 150???

The buzzer did go off one time but that was last year and have replaced everything since then with the water pump. Battery was fine

 

[Windykid]

Re: 70 lb compression on mariner 150???

Was the engine hot when this happenned or were you low on oil?

Did you suck sand in the intake?

Did you just replace the impeller or rebuild the whole water pump?

 

[lookingforluck]

Re: 70 lb compression on mariner 150???

Motor was fine, I don't kno about the sand, and complete water pump

 

[LubeDude]

Re: 70 lb compression on mariner 150???

Was your battery weak during the test....spinning slowly? I'd borrow a second guage and charge your battery before digging deeper into it. Very uncommon for a motor to eat 6 pistons at once.

I agree with this statement. I would use another guage also, one with a screw in hose. If it`s running and starting well, I can`t beleive your compression is that low.

Warm up engine on muffs, remove all spark plugs, fully charged battery and open the throttle at least half. Crank at least six revolutions untill the guage quits climbing.

Also, if you have an aluminum prop, you wou be surprised what an encouter with sand can do to the pitch of your prop.

 

[Windykid]

Re: 70 lb compression on mariner 150???

I agree to make sure the engine is warmed to operating temp.

 

[lookingforluck]

Re: 70 lb compression on mariner 150???

Stainless steel prop

 

[studlymandingo]

Re: 70 lb compression on mariner 150???

Have you re-checked your compression?​

 

[lookingforluck]

Re: 70 lb compression on mariner 150???

I have rechecked it after doing the decarbing twice, it is now 75 per cylinder, I know that it is really odd that all of the cylinders are low like that and it starts and runs fine. I did notice that the pee hole water was steaming some coming out, but temp guage says 165, The compression is what bothers me. No Power

 

[lookingforluck]

Re: 70 lb compression on mariner 150???

I haven't checked the spark yet because I don't know how and would that cause the low compression, I did check the guage on my lawnmower and I know that the guage is good.