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
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.
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?
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?
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.
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.
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.
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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.
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.
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
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.
I'm not the top expert but a couple things wont hurt to ask, they are nonengine and may be worth confirmation before digging into the engine:
1. confirmation of electrical function and that all cylinders are firing correctly, sometimes these motors start and run fine for a while and then after an hour or so the thing heats up and electrical components can fail in the field, starts surging or seems to lose power, and then they may work again when it cools off (I have a merc 90 that pulls this trick on me, i dont know exactly why yet)
2. does your prop have a break-free hub maybe it is spun.
3. 5100 seems fairly near the high end of the range too so if you were running 68mph at significantly higher than 5100 you may have overworked something?
I don't know if this will help but I had a similar problem with running aground. Did you use your motor to get off the sand bar? I used my motor to get off a sand bar several years ago. When all of the sand is swirling under water your water pump is pulling it in to the motor. That would explain the sudden drop in compression. What happened to mine and I would guess with yours is that your motor was overheating as the sand was being pumped in. My cylinders were scortched from the overheating. If the pee has slowed down as you say, the impeller was damaged by the sand thus causing the overheat and low compression.
I would pull the heads and see what you have. I am guessing that the cylinders will have heat damage and scoring. When my motor was re-built, they pulled 2 ziplock bags full of sand out of the motor. I hope this helps because the symptoms sound just like what I experienced several years ago.
70 lb compression on mariner 150???
Re: 70 lb compression on mariner 150???
Re: 70 lb compression on mariner 150???
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