1985 140 Johnson looper 20 degree temp difference between port and starboard

[roger3645]

Hi All... I am running a 1985 140 looper model J140TLCOS on a 1996 17 ft Ranger Sport R70. When warm and at idle port is at 123 degrees and starboard at 143 degrees. I replaced the starboard thermostat (140 degree stat) and there was no change. Running at 5000 rpm with trim adjusted up just enough to obtain a slight rooster tail above the engine I got an over heat alarm. I shut the motor off and checked the temps , port at 163 and starboard at 183. After the motor cooled I ran the motor again but didn't trim it up as high and it did not overheat. Water PSI remained 20 psi during both runs.

I am wondering if this 20 degree difference is the cause of poor WOT performance. Seems to be no change in speed from 5500 to 6000 rpm, 46 mph is all she will do with an entry level 14 1/4 x 21 SS prop. No jack plate and I have mounted the motor in every hole in the transom with no change in mph it only changes rpms. Hole shot is very good in any position. Runs 46 mph with a 19 pitch SS prop as well.

Plugs are QL77JC4 gapped at .40, compression 118-120 on all 4, spark jumps a 7/16 gap, Spark is crisp and white didn't notice any blue in the spark. Clean carbs with a firm bulb.

I guess I should just be happy that it runs.

So any thoughts on the temps and performance?

 

[Crosbyman]

possible water flow restrictions in the power head see utubes on flushing

 

[roger3645]

possible water flow restrictions in the power head see utubes on flushing

Thanks I will check youtube

 

[dingbat]

When was the last time you changed the impeller. I get close to 30 psi with a fresh one.

Not possible for the rpm to increase w/o a change in speed unless the props efficiency changes

Having said that, aluminum props can and do wear out over time

 

[roger3645]

When was the last time you changed the impeller. I get close to 30 psi with a fresh one.

Not possible for the rpm to increase w/o a change in speed unless the props efficiency changes

Having said that, aluminum props can and do wear out over time

I changed the impeller about 16 months ago. I am not running an aluminum prop. It is an older SS model prop # 387520 . I don't know but performance can be all prop related. I am thinking I should be running around 53 mph, 7 mph seems to be a lot to make up with a better prop.

 

[roger3645]

Also I don't believe there is any prop slip. The prop has a new hub and I marked the hub and prop and the marks are still aligned.

Further the fuel pump has been rebuilt with OEM parts, and new power pack.

 

[dingbat]

I changed the impeller about 16 months ago. I am not running an aluminum prop. It is an older SS model prop # 387520 . I don't know but performance can be all prop related. I am thinking I should be running around 53 mph, 7 mph seems to be a lot to make up with a better prop.

13% between expected (53) and actual (46) performance. Could be a bad or mismatched prop.

Have you run a prop calculator on each prop?

OE lower unit?

 

[Faztbullet]

Water pressure is low at WOT and this will effect the t-stat/poppet seating. The t-stat is not used at WOT as its bypassed by water control valve.

 

[roger3645]

13% between expected (53) and actual (46) performance. Could be a bad or mismatched prop.

Have you run a prop calculator on each prop?

OE lower unit?

 

[roger3645]

I did on the 21 pitch and got 19% slip which is pretty poor.

 

[roger3645]

On Sunday I will post a picture of where I connected the water pressure line on the motor. Possibly wrong spot.

 

[dingbat]

I did on the 21 pitch and got 19% slip which is pretty poor.

There is you missing speed....I’m at 7% with 15x15 Enertia

My water pressure gauge connects to anipple on the block

 

[roger3645]

Water pressure is low at WOT and this will effect the t-stat/poppet seating. The t-stat is not used at WOT as its bypassed by water control valve.

I have the water pressure gauge tube connected to the small water tube going to the water control valve. Got that location on this forum. Thanks for your help.

 

[oldboat1]

Unless you do a lot of slow speed travel (seems you don't), consider gapping the plugs at .030.

 

[Faztbullet]

Gauge attaches to fitting in adapter plate . As posted WP is suspect

 

[roger3645]

WP gauge is connected to the adapter plate, Checked the gauge by shooting some compressed air in the line seems to be working correctly. Dropped the lower unit and connected the ear muffs to it and turned the water on. Plugged the water outlet with my finger some water was coming out along the driver shaft, wasn't using that much water pressure from the hose. I don't know if that's normal or not. Found one of the bolts, bolting the water pump to lower unit stripped. So I went ahead and ordered an OEM water pump kit and will repair the stripped threads.

Then I attached the garden hose to the water intake and let the motor run till warmed. Found both port and starboard to be within one or two degrees of each other.

So let's hope the new water pump will take care of the water pressure problem.

I will post an update after installing new pump.

I also gapped the plugs at .30

Thanks to everyone

 

[roger3645]

Unless you do a lot of slow speed travel (seems you don't), consider gapping the plugs at .030.

I do when when using the fish finder looking for bass. Normally cruz around 38 mph.

 

[oldboat1]

WP gauge is connected to the adapter plate, Checked the gauge by shooting some compressed air in the line seems to be working correctly. Dropped the lower unit and connected the ear muffs to it and turned the water on. Plugged the water outlet with my finger some water was coming out along the driver shaft, wasn't using that much water pressure from the hose. I don't know if that's normal or not. Found one of the bolts, bolting the water pump to lower unit stripped. So I went ahead and ordered an OEM water pump kit and will repair the stripped threads.

Then I attached the garden hose to the water intake and let the motor run till warmed. Found both port and starboard to be within one or two degrees of each other.

So let's hope the new water pump will take care of the water pressure problem.

I will post an update after installing new pump.

I also gapped the plugs at .30

Thanks to everyone

Trust you mean .030.... Need back pressure -- muffs don't tell you what you need to know.

 

[roger3645]

Replaced the water pump. Now running with 30 psi and not over heating . Guess I'll try finding a better prop to help with performance. Thanks guys.