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73 evinrude 135 possible jetting issue?

R

rick peppers

Member
Let me start by saying that you guys are great and gave me a plethora of knowledge about my 115 and it is now running. So THANKS!!!!

now I’m on to a 73 135 that i picked up for cheap that runs pretty good but i wonder if it might have a small jetting issue

it is on a 17 foot 73 marlin that is by all accounts a super lightweight boat

it has a stainless 13x17 prop on it. It seems to struggle a bit off the line with a very pronounced bog in acceleration that it over cones in a few seconds and then pulls well.

the engine came with all service papers from a marina including a fresh leak down test showing 15-25% leak down

i had my kid behind it last night on a tube and this exacerbated the “bog” into a full out bog down to dying nearly every time i tried to take off

also if it sits more than about a minute i have to choke it to start it, which is pushing me towards thinking possible jetting?
 
The 73 model V-4 blocks are unique.----Nothing from 72 fits and nothing internally from a 74 fits.-----With a 17" pitch prop the boat should take of like a rocket.------Compression test is the first thing to do !!!----Post the COMPRESSION numbers you find.
 
There is one brass high speed jet located behind each of the drain screw plugs of the carburetors (4 in all), and the slightest restriction of any of them will result in what you're describing. Clean them carefully with a piece of single strand steel wire. They have 14x20 threads and can be removed via a screwdriver that has a shank that just clears the drain screw plug threads (also 1/4x20) with the regular tip cut off, then the shank filed to resemble what you see below. Or order one from this site if they stock it, or at your local dealership

Trying to use a regular screwdriver tip will usually result in jet orifice damage... As Joe Namath states in his commercials "I guarantee it!" (Ignore the price mention, Long Gone)

317002_CARB-JET_REM-INST.JPG
 
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racerone said:
The 73 model V-4 blocks are unique.----Nothing from 72 fits and nothing internally from a 74 fits.-----With a 17" pitch prop the boat should take of like a rocket.------Compression test is the first thing to do !!!----Post the COMPRESSION numbers you find.
Click to expand...

i was told by the marina here that a leak down test tells more about the engine than a compression test ever could. And all the leak down numbers are good. 17% 19% 21% and 25%
 
joereeves said:
There is one brass high speed jet located behind each of the drain screw plugs of the carburetors (4 in all), and the slightest restriction of any of them will result in what you're describing. Clean them carefully with a piece of single strand steel wire. They have 14x20 threads and can be removed via a screwdriver that has a shank that just clears the drain screw plug threads (also 1/4x20) with the regular tip cut off, then the shank filed to resemble what you see below. Or order one from this site if they stock it, or at your local dealership

Trying to use a regular screwdriver tip will usually result in jet orifice damage... As Joe Namath states in his commercials "I guarantee it!"
View attachment 21469 <-- Ignore the price mention (Long Gone)/
Click to expand...
Thanks you are always there with answers!!! I will keep you posted of results..so are you not leaning towards jetting being off?
 
Post the compression test numbers !-----Just looked at a 67 model 40 HP the other day.------Had been into a repair shop to the tune of $850 ca for work.-----Without openbing a tool box I spotted numerous problems that they overlooked.-----And according to the motor owner they did not own up to the BLUNDERS they made.-----So post the compression numbers here.----That boat should fly with a 135 HP in good condition.----And I believe the motor is NOT in good condition.
 
rick peppers said:
Thanks you are always there with answers!!! I will keep you posted of results..so are you not leaning towards jetting being off?
Click to expand...

Not Leaning??... My reply is all about leaning on the high speed jets that may be clogged.

One other thing..... Your post/reply #4 aimed at a member who advised a compression check to which you replied:
"I was told by the marina here that a leak down test tells more about the engine than a compression test ever could. And all the leak down numbers are good. 17% 19% 21% and 25%."

Your marina friend is wrong, and in refusing to enter the compression psi readings, it would surprise me if you heard from that member again. Compression psi readings speak volumes for us as does a spark test using a 7/16" air gap for the spark to jump.
 
racerone said:
Post the compression test numbers !-----Just looked at a 67 model 40 HP the other day.------Had been into a repair shop to the tune of $850 ca for work.-----Without openbing a tool box I spotted numerous problems that they overlooked.-----And according to the motor owner they did not own up to the BLUNDERS they made.-----So post the compression numbers here.----That boat should fly with a 135 HP in good condition.----And I believe the motor is NOT in good condition.
Click to expand...
I will compression test it tonight and post numbers
 
joereeves said:
Not Leaning??... My reply is all about leaning on the high speed jets that may be clogged.

One other thing..... Your post/reply #4 aimed at a member who advised a compression check to which you replied:
"I was told by the marina here that a leak down test tells more about the engine than a compression test ever could. And all the leak down numbers are good. 17% 19% 21% and 25%."

Your marina friend is wrong, and in refusing to enter the compression psi readings, it would surprise me if you heard from that member again. Compression psi readings speak volumes for us as does a spark test using a 7/16" air gap for the spark to jump.
Click to expand...
i was not refusing to give compression numbers and sorry if it sounded like that. I plan on doing it tonight
 
Ok i did a compression test. Numbers are as follows

1-125
2-130
3-130
4-130

i checked 4 times and got the same numbers

i checked the spark and it is clearly jumping a 7/16” gap

i cleaned all 4 main jets out with wire and carb cleaner

havent had a chance to test on water yet but I did notice that the primer is still having issues pulling gas from the tank wondering if that could be it?
 
Test run with another tank and hose.----Compression looks good.-----But with a 17" pitch prop the motor should not be struggling to get on plane.
 
So I bought all new fuel line, primer bulb and fittings to replace mine and in doing so I found that the previous owner had 5/16 line from the tank to the bulb and 3/4 from the bulb to the motor. Additionally there was a splice in the 5/16 line with a brass barb. I am going to test it tomorrow and am hoping this fixes the falling on it’s face problem
 
Ok. I took the boat out today and there is no difference. Still falls flat on its face when trying to get a tube out of the water???? Also I would assume that a 16’ boat with a 135hp motor that has good compression should not struggle to get to 40 mph? Any other suggestions would be welcome
 
rick peppers said:
Ok. I took the boat out today and there is no difference. Still falls flat on its face when trying to get a tube out of the water???? Also I would assume that a 16’ boat with a 135hp motor that has good compression should not struggle to get to 40 mph? Any other suggestions would be welcome
Click to expand...

Does pressing the fuel bulb when at high speed make any difference? If yes, then check fuel pressure past the VRO fuel pump. If there is inadequate pressure then it may struggle at high speeds.
 
You do not have a VRO pump about 10 yrs to early for that. Just have somebody pump the primer ball while you are accelerating. If that makes it better you probably have a fuel pump issue. Has this motor had a link and sync done to it? Have you checked to make sure all the carbs are opening all the way, and at the same time? Are all the throttle linkages in good shape? If this has a timer base is it moving smoothly?
 
I see no mention of you checking/cleaning the high speed jets... Did you? If all four must be completely clean.

Also... Check the timer base under the flywheel to make sure it isn't sticking as the throttle is applied. With engine NOT RUNNING, observe that timer base as it advances towards the full spark advance position when the throttle is slowly opened to full.
 
joereeves said:
I see no mention of you checking/cleaning the high speed jets... Did you? If all four must be completely clean.

Also... Check the timer base under the flywheel to make sure it isn't sticking as the throttle is applied. With engine NOT RUNNING, observe that timer base as it advances towards the full spark advance position when the throttle is slowly opened to full.
Click to expand...

Hi joe. I did clean all 4 high speed jets with wire and then blew compressed air through each individual jet as you suggested. I will check the timer base next
 
flyingscott said:
You do not have a VRO pump about 10 yrs to early for that. Just have somebody pump the primer ball while you are accelerating. If that makes it better you probably have a fuel pump issue. Has this motor had a link and sync done to it? Have you checked to make sure all the carbs are opening all the way, and at the same time? Are all the throttle linkages in good shape? If this has a timer base is it moving smoothly?
Click to expand...

i cannot day if it has had a link and sync performed but I will now look into it. I will check the timing advance. All linkages look good but I will for sure check to make sure the carbs are opening all the way and together
 
flyingscott said:
You do not have a VRO pump about 10 yrs to early for that. Just have somebody pump the primer ball while you are accelerating. If that makes it better you probably have a fuel pump issue. Has this motor had a link and sync done to it? Have you checked to make sure all the carbs are opening all the way, and at the same time? Are all the throttle linkages in good shape? If this has a timer base is it moving smoothly?
Click to expand...
Can you direct me to a how to for a link and sync please
 
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