Lake St. Clair Fishing Forum banner
1 - 20 of 34 Posts

·
Registered
Joined
·
27 Posts
Discussion Starter · #1 ·
went from 4800 and wot and now 4000 rpm when throttle lever is all the way down. still does about the same top speed though. what could cause this?
 

·
Registered
Joined
·
1,146 Posts
We can add to that list - fouled bottom (dirty), ignition problem, carb issues, crappy fuel, low compression.....

If it were fuel delivery, you most likely also have a bit of popping thru the carb under load.

What engine, drive, size boat?

Did you happen to get gas a Speedway at Crocker and Jefferson? Just asking because I got gas in my car there earlier this week, and have had quite a few issues since.... getting better, but it was driving like poo all week.....
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #5 ·
It is a 19ft. with a 4.3 and an OMC outdrive. does 42 tops, and 19 pitch prop.

I am going to go check if the butterfly in carb today opens all the way up.
Could putting alot of 87 octane in do this, because i notice at fuel docks it is 89 octane. could i have retarded the timing if so? from this???

When there is only two people in the boat it gets to about 37mph and then can slowly get to about 40mph when at the 4000 rpm.
 

·
Registered
Joined
·
28,072 Posts
QUOTE(gardeth81 @ Jun 25 2009, 08:06 AM) <{POST_SNAPBACK}>It is a 19ft. with a 4.3 and an OMC outdrive. does 42 tops, and 19 pitch prop.

I am going to go check if the butterfly in carb today opens all the way up.
Could putting alot of 87 octane in do this, because i notice at fuel docks it is 89 octane. could i have retarded the timing if so? from this???

When there is only two people in the boat it gets to about 37mph and then can slowly get to about 40mph when at the 4000 rpm.

Octane won't change ignition timing, but it can effect performance. If the tank is half full or less I would top off with some higher octane gas. If it's still pretty full, add some octane booster and see if that makes an improvement.
Some engines just need more octane than others and driving habits can show it. Case in point, I have two Mustang GT's I can run the 91 with auto trans on 87 octane, but if I put 87 octane in the 89 with a 5 speed and drive it the way it was made to be driven, no way, it will stumble off idle and backfire at mid-range and higher RPMs.
When you check the carb, look at the fuel filter and fuel line, just to be sure thats not part of the problem. Clean or replace the plugs, if it's running rich at all, the low RPM from all that trolling will load the plugs, check idle mixture, see if you can lean it out a bit and still get good idle quality out it.
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #7 ·
I was wondering, there is a fuel filter on the motor, it looks like an oil filter, is this an fuel/water filter could this be a cause. because after or around the wot rpm issue it had backfired and missed and stuff. So harbor master said that we had water in our fuel tank and put in some stuff for this and it had cleaned it up.

It runs and idles fine. Thanks.
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #9 ·
Thanks for the thread big dog, this may be the problem. to replace this filter should i fill it up with gas when i replace it. to help with restarting? Do i have to go to a marine store to buy or do they carry them at autozone etc.
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #11 ·
Thanks, i will try one thing at a time to troublshoot and i will let all know later what problem is.

Electric is my speciality.
 

·
Registered
Joined
·
28,072 Posts
It's not mine
but I'm about to become and electrician anyway. Front and rear nav lights are out, leading me to believe it's a fuse or ground problem. Worked fine last year, this year both front lights and the rear are not lighting. I can't believe three bulbs went bad all at once. Dash light are fine but I believe they are on a separate circuit.
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #13 ·
So far checked throttle linkage- good, opens butterflys all the way. guessing that the automatic choke stuff is all fine. still 4000 rpm. next spark plugs, still 4000 rpm. then fuel water seperator. still 4000 rpm. she does do the same speed though 41 tops, but then i guess that i did notice the rpms get to 4100 also. My dad is happy with this cause he is running lower rpm and doing same top speed than must mean he is saving gas. Manual does say that wot should be 4800 rpm when the right prop is on. Maybe our prop had stretched flexed, it is an aluminum prop. Ohh, also checked the points and the spec. was good. Also when i checked the gap on the old spark plugs they had stretched than the specified gap to run ( this is normal im sure after time).

Ohh, a good way to check the lights like that are to follow the wires if you dont no which wires the are, could be the bulbs, or a fuse, or the switch, pretty simple. Let me know if any questions, im not to far from eastpointe neither.
 

·
Registered
Joined
·
22,943 Posts
QUOTE(gardeth81 @ Jun 25 2009, 04:16 PM) <{POST_SNAPBACK}>So far checked throttle linkage- good, opens butterflys all the way. guessing that the automatic choke stuff is all fine. still 4000 rpm. next spark plugs, still 4000 rpm. then fuel water seperator. still 4000 rpm. she does do the same speed though 41 tops, but then i guess that i did notice the rpms get to 4100 also. My dad is happy with this cause he is running lower rpm and doing same top speed than must mean he is saving gas. Manual does say that wot should be 4800 rpm when the right prop is on. Maybe our prop had stretched flexed, it is an aluminum prop. Ohh, also checked the points and the spec. was good. Also when i checked the gap on the old spark plugs they had stretched than the specified gap to run ( this is normal im sure after time).

Ohh, a good way to check the lights like that are to follow the wires if you dont no which wires the are, could be the bulbs, or a fuse, or the switch, pretty simple. Let me know if any questions, im not to far from eastpointe neither.
If you're getting the same WOT speed, then it must be something with the tach (as Dos mangos said).

What about other RPM operating ranges? Also showing reduced RPM at the same speed?
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #15 ·
i think the same as was before. not to sure, i have never been capt.
this year before the so called problem occured. Don't remember last year either.
 

·
Registered
Joined
·
28,072 Posts
I might have an older aftermarket tach around somewhere??? in the garage that you could borrow and hook up to compare the readings with yours.
I'll do some hunting around in the garage this weekend and see if I can find it.
 

·
Registered
Joined
·
22,943 Posts
QUOTE(gardeth81 @ Jun 25 2009, 09:56 PM) <{POST_SNAPBACK}>i think the same as was before. not to sure, i have never been capt.
this year before the so called problem occured. Don't remember last year either.
If everything else seems the same (top speed, fuel consumption, etc.), perhaps you have more a quirk than a problem.


Good luck!
 

·
Registered
Joined
·
22,943 Posts
QUOTE(gardeth81 @ Jun 25 2009, 10:06 PM) <{POST_SNAPBACK}>yeah i wish i new what kind of fuel consumption i was getting.

Thanks big dog
Well, I can say this with much certainty...

You will consistently find maximum consumption at WOT!


Sorry, I know that doesn't help, but couldn't resist!
 
1 - 20 of 34 Posts
Top