Logo
FULL SITE MENU

Tuning a 1986 30 4clyinder omc140hp

J

jrod1540

Contributing Member
"ok so here is the deal i have

"ok so here is the deal i have an 86 3.0 omc on a 17 foot sea ray seville not the biggest boat in the world and other bigger boats are getting up to 40 with this motor but i barely break 30 and feel like i have not pulling power at all. also the boat kinda has a dead spot every now and then and once i get the throttle past about half way i dont feel any more power out of it from half way to full open.


here is what i have done.

head checked out ok.. new exhaust valve and new seals

new head gasket, exhaust gaskets and all the other s when doing a job like that, new thermostat as well

i put new impeller in it

new gas filters

rebuilt the carb have the air bleed screws about to turns out as recommended

it has an electronic spark that replaced the old points

the timing is set at 5 degrees BTDC

not sure if thats too much could find the exact timing for the motor


but when i get on the throttle the thing just has no power it takes in like two minutes and once it planes out then it slowly picks up speed


and i put a new prop for waterski to get more pull power.... 13 1/4 by 17

also put a fin on the back to help it plane


is it a timing issue im just really off on something to ceck for the carb any advice would be greatly apprecitated"
 
Timing should be 1deg ATDC wit

Timing should be 1deg ATDC with 86 Octane. If running 89 Octane set it at 4deg BTDC.}
 
yea checked the throttle after

yea checked the throttle after i rebuilt it . . .i played with the distributor a little yesterday i think ill try that out and se how she runs and then go back check the timing again to make sure i good but what does AKI 86 mean ??
 
two turns is just for starters

two turns is just for starters then you fine tune the carb
 
"AKI (Anti Knock Index&#4

"AKI (Anti Knock Index) think of it as the octane level of the fuel. Most marinas around use at least 87 if not 89, it does make difference how you set the timing.

Remember those 2 turns for the carb are just for the low speed circuit, the hifh speed should be a fixed jet. Those RPM's are way too low, was the drive ever replaced on this, can you post the model # off the drive, just wondering if the gearing is wrong, ave you always had this problem since you owned the boat?"
 
YES THE TRIM SUTEM IS WORKING

YES THE TRIM SUTEM IS WORKING I JUST REPLACED THE MOTOR IN APRIL. . .SORRY FORTHE ALL CAPS WRITING THIS OFF MY PHONE
 
alright bob heres the deal the

alright bob heres the deal the other day i was i self timed the motor by sound and the take then adjusted idle ... took it out think i was using premium cause thats all they sell on the lake.... boat ran great was pushing almost 45 at like 4000 rpms and that topped it out.


so then i was think i must be really close to 1atdc that it calls for... yesterday i borrowed a timing light ad i was at like 5BTDC... so adjusted it to 1ATDC.. but when i took it out it would barely get up to 10mph (using reagular unleaded).


so i readjusted it by hand on the lake and it started running at about 35 mph aat 3700 ... thinking i pushed back to 4 or 5 BTDC... what are your thoughts on this :

i was think some of its gas im using but thats a far as i can get and i dont want to keep running it and mess up the pistons if it hasnt got enough octane.


thanks a bunch
 
If your running Premium or any

If your running Premium or anything above 86 then the 4BTDC should be good to go for you. Try to borrow that light again and set it at 4.
 
alright i was also reading tha

alright i was also reading that forum about mark when he had the esa problem cause im getting dead spots where it kills the motor every now and then right out of gear so i checked it and the roller was going on the peak so i tried to adjust the cables accordingly but its either easy to switch in and out of forward and it wont budge into reverse or vice visversea any more help you could lend would be great ...

man if it wasnt for you id probably never have the motor running properly(well almost) or id have spent a lot of money on simple adjustment from a mechanic thanks for all your help
 
"Follow the link that Chuck pu

"Follow the link that Chuck put in, especially if you don't have the original OMC factory manual, a lot of those cable adjustments/checks need to be done sequentially. You may have to start from scratch and go through each one in order. It's also possible you could have a binding or stretched lower shift cable."
 
HOW DO I KNOW IF I HAVE THE RE

HOW DO I KNOW IF I HAVE THE REPLACEMENT CABLE OR THE FAULTY ONE...IM KINDA ASSUMING IT HAS BEEN REPLACED CAUSE THE BOTTOM SHIFT CABLE IS RED . . . .CHUCK THAT LINKS IS GREAT BOTH ADJUSTMENT AND HISTORY OF OMC ...
 
If you have the red one then y

If you have the red one then you have the revised good cable but that's not to say the cable hasn't gone bad over the years. It's been a long time since that cable came out.
 
all marinas in my area sell re

all marinas in my area sell regular 87 octane. They just charge a premium price for it.
 
Back
Top