johnson is slow to get going but then goes fine

[roofcock]

i have a 1976 johnson 85 hp on a champion bass boat. when i push the throttle down to take off instead of a nice hole shot it slowly builds power as the boat starts to plane and then picks up rpms and goes fine. does this sound like a starving fuel delivery or could it be getting too much fuel while accelerating or.... i have no idea so i was hoping someone else did. i had a 1981 evinrude 85 hp on the same boat i took off for repairs and didnt have this issue while using that motor. i know the boat is not to big for the motor (17' 6") so i assume (and we all know what happens then) it is fuel
thanks for looking any ideas would be most appreciated

 

[phillnjack2]

Re: johnson is slow to get going but then goes fine

well the 76 85 hp is not the same as the 1981 for starters.
the cubic capacity might be a huge difference.
the 76 is probably crossflow and the 1981 will be a looper i would guess.
in 76 it was 85hp at the prop, by 1981 it could be 85hp at the flywheel !!!! big difference.
that would equat to a 1976 115hp and that could be the answer .

what is the model number of the 1981 85hp
what size prop are you using on this motor ?
is it the same prop as the other engine or a bigger pitch or diameter ?
if the pitch is bigger then it wont be as quick for holeshot.

what is the compression on each cylinder for the v4 85 your running now ?

 

[boobie]

Re: johnson is slow to get going but then goes fine

Check your timer base plate under the flywheel to make sure it's free.

 

[roofcock]

Re: johnson is slow to get going but then goes fine

the model numbers are J85TLCSA its a 1980 not 81 as stated before. the other is 85ETLR76G. the compression on both engines last time i checked them was 110 to 115 on all cylinders. the 1980 came on the boat. the 1976 was on another boat i had that sunk. on the other boat it had a decent hole shot. the other boat was monarch tri hull and this one is a super v both approximately 18 ft long. i have not compared props. the props are the ones that were on both motors when i got them. i check my timer base before as that was how i got it to stop cutting off as i applied throttle. with the 80 i could stay seated to get on plane with the 76 it makes it better if i lean forward to help it get on plane. then it will start to plane and the power will come on. maybe just to check i should swap props between the two if they are different from one another. but if the 76 has the 85 at the prop and the newer on has it at the flywheel wouldn't the 76 have more power or am i missing something

 

[phillnjack2]

Re: johnson is slow to get going but then goes fine

sorry i got it the wrong way round when i posted that...9cant believe i done that ha ha ).

no the 1976 was rated horsepower at flywheel.
the later engines were rated at propeller.
this means the older 1976 engine would only be around 65-70 at the propeller. !!!! a very big difference on that size boat.
also there is possibly a different gear ratio as well between them im not so sure.

i would definitely have a look at the props for sizes and condition, and swap them over to try anyway.

the v4 engines all look pretty much alike, but they can have huge amounts of differences wehn you delve into them.

The hulls can also be identical make and model,it dont mean the one you have now is not full of wet soggy foam or
will run the same !!!!
silly stuff like a dirty bottom with algae on the hull can make a bigger difference than you might think as well.
do check those prop numbers,it could be a prop giving the wrong ratio,it would cause bad holeshot and bad top end revs if
its too big in the pitch.
i would say a 13x15 or 13x17 is all that engine needs.
if its 19 you just might get away with it but not on the hole shot.

phill

 

[roofcock]

Re: johnson is slow to get going but then goes fine

thank you for your response i will check the props today. i am waiting on a trim pump to be able to haul it to the lake and check if there is a difference. i will post what i find.

thanks

dennis