83 johnson 140 v-4

[tblshur]

thanks for any replies. i have j140tlcte ,83 140hp .ive driven a friends 85, 88hp v-4 when putting boat on trailer it will throdle up and really push the boat. my boat acts like it just will go to maybe 2500 rpm or so , it wont push the boat really hard on the trailer.my boat is slow getting on plane, otherwise it runs great. could that be a timing problem:joyous:

 

[racerone]

Timing is fixed and rarely needs adjusting for the life of the motor.------Start the trouble shooting with a compression test.----Then check for spark that MUST jump a gap of 7/16" on all 4 leads.

 

[tblshur]

thanks racerone for the quick reply. the compression is 96 psi on 3 and 98 on 1 . the coils are suspect. spark jumps 7/16 gap but is skinny and i think may skip sometimes cant see as good as i use to, will check real good. thanks again for your help:joyous:

 

[emdsapmgr]

Any chance you have the wrong pitch prop on the engine? An incorrect pitch prop can seem make the engine sluggish. What WOT rpm's will that engine run-flat out with full trim?

 

[tblshur]

thank you emdsapmgr im at lake now and it showed 5000rpm gps was 43mph have some wind prop is ss j&e 19 thanks again for your help

 

[Bosunsmate]

post a video of it if you can, sometimes a waterlogged hull will have your boat struggle to get up

 

[emdsapmgr]

That engine should run 5500 rpm's at WOT. With that year 140, it should still make solid, reliable hp up to 5700, so your engine/boat is overpropped with a 19 stainless. The engine is lugging and probably slow out of the hole. You need to go down at least one prop pitch. If you go to a 17 pitch, you should pickup about 300 rpm's, still just short of your rpm target. If you can borrow a 17 try it, you won't believe the performance difference.

 

[tblshur]

thanks again emd i will try to borrow another prop and try , will post back if i can

 

[tblshur]

emd you really nailed it , a nice mechanic loaned me a used alum and a ss 17 pitch prop they both would mak:joyous:e the boat jump up on plane ,i did lose about 5 or so mph the motor sounds much better guess ill start a prop fund soon thanks again to all u guys on this forum:thumb:

 

[metriccrescentwrench]

..... they both would mak:joyous:e the boat jump up on plane ,i did lose about 5 or so mph .....

I'm actually surprised you lost speed with the prop change, the engine is probably making more power at 5500 rpm than it did at 5000, it could just be that the prop you tried wasn't in the greatest of condition (which would affect it worse at the top end). In any case you've found that the boat will perform much better with a prop that gets you up near the top of the rpm range. It's also better for the engine (less chance of carbon sticking the rings and lower internal pressures). I had an '81 90 and it would happily rev to 5800 rpm.