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1987 Evinrude E120TLCUR V4, NO THRUST

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Fisherman13

New member
I just repaired the #2 piston in my 1987 Evinrude E120TLCUR V4 and once the engine put back together and taken foe a test ride it was immediately discovered there was no thrust. The thrust problem existed prior to replacing the piston, however I thought the lack of thrust was resulting from compression problem with the piston. Has anyone had this experience?
 
Explain the lack of thrust in more detail..... does the engine race away and the boat goes nowhere, the engine does not obtain a natural high rpm, what?
 
Either your engine is set too high on the transom, OR and most likely, the hub within the propeller is slipping. Remove the prop nut, then mark a line with a magic marker on the hub into the propeller. Reinstall the nut assembly then test the rig to obtain the problem. Now, remove the nut again to observe the line you made. If the mark is no longer aligned, the hub is slipping, in which case replace the propeller or have it rehubed.
 
1987 E120TLCUR V4 with VRO, just replaced #2 piston and after checking and rechecking all connections and system. Now even at full throttle can not get boat up to speed or very, very little forward movement.
 
It was suggested to try another prop or at least check it for slippage.----What was the result of that inspection / testing ?????
 
Sounds to me like the prop.. and he rebuilt an engine instead of checking for something obvious. Jeez.
 
The engine was rebuilt because of a blown piston, once the engine was re-installed then the thrust problem surfaced. We have since checked everything including the prop and the problem still exist. Please ask questions before you jump to conclusion next time. Jeeez, thank you anyway.
bill_w said:
Sounds to me like the prop.. and he rebuilt an engine instead of checking for something obvious. Jeez.
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Fisherman13 said:
The engine was rebuilt because of a blown piston, once the engine was re-installed then the thrust problem surfaced. We have since checked everything including the prop and the problem still exist.
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Only two things will cause a engine to race away and have the boat slow down as you verified in post #3, and that would be a slipping propeller hub or cavitation due to the engine being mounted too high.

Am I correct in assuming that if you drop the rpms, the prop once again takes hold?

Of course, there is always the chance that the boat has developed a hook in its hull, resembling a gigantic trim tab that is raising the stern of the boat as its speed increases.

Then there is the stripped driveshaft spline or the sheared driveshaft scenario, BUT that's not a come and go situation.

You say the propeller is okay... did you do the magic mark test or use another known good propeller?
 
Fisherman13 said:
I just repaired the #2 piston in my 1987 Evinrude E120TLCUR V4 and once the engine put back together and taken foe a test ride it was immediately discovered there was no thrust. The thrust problem existed prior to replacing the piston, however I thought the lack of thrust was resulting from compression problem with the piston. Has anyone had this experience?
Click to expand...

Hey, you said it was there before the rebuild, and you thought that the cause was low comp on one cylinder. Don't blame me if I read and respond to what's written.
 
Sorry, you are correct but the piston was blown and needed to be rebuilt anyway. Being a layman I should have written the post as: Problem 1. blown piston, Problem 2. no thrust. Please understand I do appreciate all the advise the members are giving and I don't mean to offend anyone. Thanks to all.
 
This is going nowhere fast--------Couple of points I can make------Was the cause of the blown piston found and corrected ?---------Have you now tested for a bad / slipping propeller ?--------Is the motor still installed on the same boat as before the rebuild ?--------What is the transom height of the boat ?-------------Only good answers to these points will help you in sorting this out.
 
I should said from the beginning that I am new at this and don't understand many of the terms and descriptions used, however I am glad to get the help. So could you explain what hook in the hull means and look like. Thanks.
 
Was the cause of the blown piston found and corrected? Yes. Engine is running good. Have you now tested for a bad / slipping propeller? Yes, marked and checked propeller, no slippage. Is the motor still installed on the same boat as before the rebuild? Yes, only the upper part of the motor was removed to repair piston. What is the transom height of the boat? 22". Thanks for using this approach.
 
Perhaps the motor is sitting too high.A standard transon height is 20" for a long shaft motor.----------Did you find out why the piston had to be replaced ???-----If not then you may have to do the same repair again soon !!---------ONE LAST OBSERVATION-------Is the shift rod properly set and hooked up in order to shift into gear ???
 
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QUESTIONS!

1 - Am I correct in assuming that if you drop the rpms, the prop once again takes hold?

2 - Did you do the magic mark test or use another known good propeller?

3 - Is the cavitation plate above the propeller 3/4" below the keel at the transom?

4 - Is the cavitation plate parallel with the bottom of the boat?
 
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