25 Johnson Waterflow Trouble

K

kajnjim

Petty Officer 3rd Class
Joined
Jun 18, 2005
Messages
87
1977 25hp Johnson Model 25R77S<br />Water output gradually decreases as throttle is increased. At approx. 1/2 throttle, all water flow stops until I let off the throttle. I thought this was caused by water pump, so I changed it. No improvement. Motor is running fine. Appreciate any suggestions.<br /><br />Jim
 
S

Solittle

Fleet Admiral
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Apr 28, 2002
Messages
7,518
Re: 25 Johnson Waterflow Trouble

Are you running it with the muffs? Also water flow from where?
 
K

kajnjim

Petty Officer 3rd Class
Joined
Jun 18, 2005
Messages
87
Re: 25 Johnson Waterflow Trouble

SoLittle,<br />Running on the water. No muffs. Output reduction/stoppage noted at the telltale and the twin exhaust holes that normally spray. It seems all water output from lower unit decreases and then stops as I throttle up. Ran in neutral in tank yesterday (to test after replacing water pump) and everything seemed ok.<br /><br />Jim
 
B

btraplin

Recruit
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Apr 10, 2002
Messages
5
Re: 25 Johnson Waterflow Trouble

Had the same problem with my 1980 35HP Evinrude a couple of years ago, turns out the head gasket was blown, but was still strong enough to hold compression pressures at low to mid RPM but as soon as the rev's got past mid point the combustion pressures leaking past the gasket into the water jackets would overcome the water pressure from the pump and hence the water flow stopped, also had some hissing coming out of the telltale & mid-section exhaust/water outlets immediately after shutdown. New gasket & thermostats, no problem.<br /><br />Cheers
 
K

kajnjim

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Jun 18, 2005
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Re: 25 Johnson Waterflow Trouble

Flthd,<br />That's what I was afraid someone would suggest. I haven't noticed the hissing, but have been careful not to let it get too hot. I guess I'll have to check it out.(head gasket) Thanks.
 
K

kajnjim

Petty Officer 3rd Class
Joined
Jun 18, 2005
Messages
87
Re: 25 Johnson Waterflow Trouble

Have changed the head gasket and head cover gasket. Flow from tell-tale has improved, but still not able to run at WOT without losing flow. As water output decreases and eventully stops, I notice a small amount of white smoke from tell-tale. When I throttle down, the amount of white smoke from tell-tale becomes heavy. I'm stumped. Is it possible that there is something wrong with the water pump that I overlooked when I serviced it??? Sorry it took a while to get things done...the life of an ER nurse in south Louisiana doesn't allow for alot of free time and of course things are even worse now. As always, any help is appreciated.<br /><br />Jim
 
G

Goodoleboy

Chief Petty Officer
Joined
Nov 20, 2003
Messages
555
Re: 25 Johnson Waterflow Trouble

I suspect the drive shaft is sliping inside the water pump.<br /><br />Make sure the little key is put in proprely. If memory serves me rite, the sharp edge goes forward with shaft rotation. Clockwise.<br /><br />(And my best wishes to you and your fellow LA. citizens. The nation is behind you all <br /><br />"The Big Easy"...will shine again Iam sure!)<br /><br />Good Luck!
 
K

kajnjim

Petty Officer 3rd Class
Joined
Jun 18, 2005
Messages
87
Re: 25 Johnson Waterflow Trouble

Thanks for the suggestion. I'll check it out and see what I got. Thanks also for the good words.<br /><br />Jim
 
K

kajnjim

Petty Officer 3rd Class
Joined
Jun 18, 2005
Messages
87
Re: 25 Johnson Waterflow Trouble

Hey fellers,<br />I got to thinking about something. Tell me what you think. I failed to mention in previous posts that I have a "doel-fin" on this motor. Could it be that this may be causing a "dead space" or cavitation that is allowing for a decreased intake at the water intake and allowing exhaust to be sucked up into the water intake, accounting for the decreased water output and presence of white smoke (?exhaust) from the tell-tale? Anybody see such a thing before? Thanks again in advance.<br /><br />Jim
 
U

umblecumbuz

Lieutenant Junior Grade
Joined
Sep 25, 2004
Messages
1,062
Re: 25 Johnson Waterflow Trouble

Jim,<br /><br />Never heard that one before, but I'm sure a lot of boaters here would be interested to find out if the fin has anything to do with your water pressure.<br /><br />Post back your findings please.
 
M

martinphantom

Seaman Apprentice
Joined
Jul 12, 2005
Messages
47
Re: 25 Johnson Waterflow Trouble

Mine's doing the same thing. I recently raised my motor 2 1/4 inches and I wonder if it's too high? Back off throttle and it starts flowing again. Some little puffs of white smoke too. 25 j 86 model
 
M

martinphantom

Seaman Apprentice
Joined
Jul 12, 2005
Messages
47
Re: 25 Johnson Waterflow Trouble

Mine's doing the same thing. I recently raised my motor 2 1/4 inches and I wonder if it's too high? Back off throttle and it starts flowing again. Some little puffs of white smoke too. 25 j 86 model
 
K

kajnjim

Petty Officer 3rd Class
Joined
Jun 18, 2005
Messages
87
Re: 25 Johnson Waterflow Trouble

MP,<br />The head gasket looked pretty good actually, but the head cover gasket was fried. I changed them both anyway and resurfaced, also replaced the t-stat that had been removed. What was yours doing before you raised it? I'm actually a hair under the bottom of the boat with mine. Tried fiddling with the tilt also, without any change. I'm interested to see if anyone has heard of anything like what I'm theorizing.<br /><br />Jim
 
P

patenglish

Petty Officer 3rd Class
Joined
May 14, 2005
Messages
93
Re: 25 Johnson Waterflow Trouble

Did this just occur, or has it always been a problem? If you have raised the engine, you might try lowering it one hole to see if this helps.
 
K

kajnjim

Petty Officer 3rd Class
Joined
Jun 18, 2005
Messages
87
Re: 25 Johnson Waterflow Trouble

Mean,<br />New problem, and the motor has always been where it is now. The more I think about it, the more I want to think it has something to do with moving through the water, because I can throttle her up in a tank and maintain strong flow through the tell-tale while stationary in the tank. My setup will not let me drop the motor any lower either.<br /><br />Jim
 
M

martinphantom

Seaman Apprentice
Joined
Jul 12, 2005
Messages
47
Re: 25 Johnson Waterflow Trouble

I don't know how long mines been doing this. I normally look to make sure I have a working water pump when I start out-never paid a lot of attention at WOT as I'm watching where I'm going. The only reason I caught it now-was hooked up on a trailer trying to adjust the carb. Don't really want to pull the head unless it's necessary. If it was doing this on a trailer-I don't think my raising the motor could be the culprit.
 
K

kajnjim

Petty Officer 3rd Class
Joined
Jun 18, 2005
Messages
87
Re: 25 Johnson Waterflow Trouble

Just an interesting side note: After changing the drive shaft seal which took a couple of days because of time constrictions, I reinstalled the lower unit and cranked her up and absolutely no water output from the tell-tale. Shut her down and a few minutes later, with a perplexed look on my face, I noticed a dirt dobber flying around the tell-tale. Disconnected tell-tale hose at the water jacket and tried to blow through it. Nothing. Ran a stiff wire through it and yes the little sh_t had done made a nest in my tell-tale hose :D He's dead now. I keep a small cap on the end now and I'm just waiting for the day I forget to take it off and shoot it across the river. Any way, that was just coincidental, as I still have the water flow problem.<br /><br />Jim
 
K

kajnjim

Petty Officer 3rd Class
Joined
Jun 18, 2005
Messages
87
Re: 25 Johnson Waterflow Trouble

Also had the same thing happen to my 4-wheeler air intake. Makes it run kinda rough. It has a piece of screen over the front now :) <br /><br />Jim
 
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