right prop

birddog07

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new to me 1990 201 stratos trying to get right prop set up. 20in running 6700 rpm . 24in running 4700 rpm. both rakers.
 

dingbat

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new to me 1990 201 stratos trying to get right prop set up. 20in running 6700 rpm . 24in running 4700 rpm. both rakers.
Something isn’t right…

What motor?
Limiter should have picked in long before you get to 6700 rpm

What speed (GPS) at those rpm?

4” change of pitch should result in a 400 rpm change, not 2,000 rpm.

Check the accuracy of the tach
 

birddog07

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Something isn’t right…

What motor?
Limiter should have picked in long before you get to 6700 rpm

What speed (GPS) at those rpm?

4” change of pitch should result in a 400 rpm change, not 2,000 rpm.

Check the accuracy of the tach
225 johnson . low 50s on the speed. the motor is between 88 and 92 i think no numbers ser or welch plug. i want to check timing after getting omc service manual but not sure on year
 

dingbat

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15,417
225 johnson . low 50s on the speed. the motor is between 88 and 92 i think no numbers ser or welch plug. i want to check timing after getting omc service manual but not sure on year
The WOT on that motor is 5,000 to 6,000 rpm. If you tach is showing 6,700 that needs to be sorted out

Serial number plate should be on transom bracket
 

jimmbo

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Any damage to any of the Blades on the 20". There shouldn't be that big of change between 4" pitch. I could accept a 1000 rpm difference, but not 2000
 

birddog07

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Any damage to any of the Blades on the 20". There shouldn't be that big of change between 4" pitch. I could accept a 1000 rpm difference, but not 2000
A little bit on the 20" not bad .I was thinking about 1000 rpms to.i want to set timing and make sure that is good first and then try to get props right.waiting on omc service manual in mail now. I went with a 1990 year hope that is right cant find any numbers at all . Ser and model number plate on transom is gone and welch has been replaced just showing a part number on it..
 

birddog07

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Something isn’t right…

What motor?
Limiter should have picked in long before you get to 6700 rpm

What speed (GPS) at those rpm?

4” change of pitch should result in a 400 rpm change, not 2,000 rpm.

Check the accuracy of the tach
I know to much rpm change. But 200 to 250 rpm per inch pitch should be about right I think so 1000 rpm change was what I was suspecting. It's a older looper 225 johnson.85 psi on all 6 holes I know is low but very even on all cylinders. Not sure on year its between a 89 and 91 . I went with a 1990 omc service manual waiting on delivery in mail now
 

jimmbo

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The Timing should not need Setting or even Checking. OMC used to put a bit of Glue/Adhesive on the Adjusting Points just to discourage People from messing with them, as most Tinkerers have no clue as to what they are Changing, and then can't remember how far they changed it, making it difficult to return the engine where it was.

When you order Service Manuals, you really need to be specific, as there can be differences, some minor, other Major between yrs. Same goes for Parts Lists.
85 psi on a Looper? Either that engine is very worn out, or the Gauge you used is out to lunch. How many Revolutions did you crank it while doing the Test? Were all the Plugs out, at the time?
 

jimmbo

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A picture of the Cowl can help a lot in determining its Yr, sometimes the engine is the same year too
 

birddog07

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The Timing should not need Setting or even Checking. OMC used to put a bit of Glue/Adhesive on the Adjusting Points just to discourage People from messing with them, as most Tinkerers have no clue as to what they are Changing, and then can't remember how far they changed it, making it difficult to return the engine where it was.

When you order Service Manuals, you really need to be specific, as there can be differences, some minor, other Major between yrs. Same goes for Parts Lists.
85 psi on a Looper? Either that engine is very worn out, or the Gauge you used is out to lunch. How many Revolutions did you crank it while doing the Test? Were all the Plugs out, at the time?
All plugs were out. Throttle was wide open. Turn five revolutions until gauge does not climb anymore. And I use two different gauges. I know the motor is very worn but all six are reading exactly the same. Even the bottom cylinder is reading the same
 

birddog07

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jimmbo

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A very worn engine is never going to run very well. With the Compression Numbers you posted, I doubt it will even start/run when on a Boat in the Water.
Perhaps all the rings are stuck. Tilt the engine up as far as it will go and secure it up. Get some Mercury/Quicksilver Power Tune or BRP Engine Cleaner, and spray Copious amounts into the Spark Plug Holes, using the Straw to get it all around where the Piston and Cylinder interact, then let sit. After several hours, rotate the engine 180 degrees and repeat. Again after several more hours, lower the engine and expel the Cleaner, and then repeat the entire Process. After the second Expulsion, redo the Compression Test. Don't worry if the Throttles aren't open, on a 2 Stroke, at Cranking Speeds the Exhaust port will fill the Cylinder with air as the piston exposes it
 
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birddog07

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A very worn engine is never going to run very well. With the Compression Numbers you posted, I doubt it will even start/run when on a Boat in the Water.
Not uncommon for older loopers to have 80 psi.they are low compression motors to start with..already have it to 55mph on 201 pro hull .grated 95 to 110 psi new would be great but it is all even
 

airshot

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With the compression being even, the motor may run welk and even make peak rpm, but the low compression keeps the motor from making peak HP... Under load your motor will be weak. I would try the ring free stuff, it just might help
 

birddog07

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With the compression being even, the motor may run welk and even make peak rpm, but the low compression keeps the motor from making peak HP... Under load your motor will be weak. I would try the ring free stuff, it just might help
Great thanks
 
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Feb 23, 2022
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What's the compression ratio of the motor? The expected amount of compression on a test should be 14.7 x compression ratio.

I've heard of some old motors being ~6:1 compression ratio, which would only give you about 90psi of compression.
 
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