2000 Mercruiser 4.3l Thunderbolt 5 ignition

[Doctom]

Ok
My 2000 Sea Pro 210WA with a 2000 Mercruiser 4.3l with Thunderbolt 5 ignition idles and takes throttle great on the trailer with the muffs and garden hose. However when it is put in the water it still idles great and will go into gear and take a little bit of throttle. And I do mean A LITTLE throttle.
After about 2,000 RPM, it does not take any more and will not go faster or get on plane. I but it the shop and the mechanic rebuilt the carb. as well as trying a replacement carb., as well as changing plugs, wires, cap and rotor.
PLEASE HELP, I just want to go fishing on my boat and be happy again.

Thanks for the help.

 

[Rick Stephens]

Two things needed, fuel and spark. Seems you have spark. My bet is the carb still has mid-range ports plugged up.

 

[Doctom]

How exactly would I find that out
Keep in mind that the mechanic I took it to put a Webber fresh from rebuild on my boat and it done the same thing as with my Holley which is also freshly rebuilt.

 

[alldodge]

I would suggest a compression test

 

[Rick Stephens]

Well, trying a rebuilt one and a second carb is pretty definitive.

 

[Bondo]

Ayuh,.... Welcome Aboard,...... Has anybody examined the Contents of the fuel filter for anything but clean fresh gasoline,..??

Has the fuel pressure from the fuel pump been checked,..??

 

[Doctom]

A compression test has been done by me and the mechanic both yielded 150 P.S.I across the board if I remember correctly.
As to checking the fuel filter/separator and fuel pressure, that has not been done by me. As soon as I get the boat back home, those are the first 2 things I will check.
I have done some research myself as well as pulling from my experiences as a Land Mechanic(Cars and Trucks and Such), it seems that timing is not advancing as it should. That being said, Could the Ignition Control Module or something in that arena be bad or heading that way?

 

[alldodge]

150 P.S.I across the board

mechanic rebuilt the carb. as well as trying a replacement carb., as well as changing plugs, wires, cap and rotor.

Like brand new compression numbers
TB-5 ignition which starts good, idles fine
Carb rebuilt and even with another carb same issue

Even with weak fuel pump you would get more then just a little throttle before dying. Not getting on plane can be lack of fuel, but with other issues still not clear.

If everything is correct in this thread it leads me to timing and need a carb fixed

 

[nola mike]

Bad gas/water in gas tank. Like Bondo said, check your water/fuel filter. Maybe crack a fuel line into a container to see what kind of gas you're pumping

 

[Doctom]

I am picking the up today from the mechanic.
I will check the fuel/water seperator filter and post what is found along with doing a fuel pressure test.
Is there a way to test my ignition sensors and modules to make for sure that all are operating properly?

 

[nola mike]

.
Is there a way to test my ignition sensors and modules to make for sure that all are operating properly?

Are you getting spark?

 

[Rick Stephens]

I am picking the up today from the mechanic.
I will check the fuel/water seperator filter and post what is found along with doing a fuel pressure test.
Is there a way to test my ignition sensors and modules to make for sure that all are operating properly?

Yes, use an advance type timing light. At idle around 8º BTDC, ease your throttle up to 2k and you should see 24-26º advance.

 

[Doctom]

Ok
I got to play with my boat today and here is what I found: Fuel Condition: Good
Fuel Pressure: 3 to 4 running(seems low to me but according my research it is Good)
After going through the troubleshooting tree provided by Don S, I need to replace the sensor in my distributor, I also done the timing advancing test and would only get 16 to 17 degrees advance with the engine at 2k to 2200.
PLEASE be advised and keep in mind that these test mentioned above were done on the trailer with muffs and the garden hose.

 

[Doctom]

I also found the engine casting number which is: 14099090M.
I also found the number K288 further towards the center of the back of the motor.
The Mercruiser serial number tag is gone, so this is the best I can get.
Is there somewhere to get engine specs such as year and fuel intake system and such?

Thank You All

 

[Doctom]

Ordered the needed replacement part(ignition sensor in the distributor cap) and go it installed today. Engine started and ran better, but according to my timing light, it still would not fully advance.
What should be the next step?

Thank You All

 

[alldodge]

timing advancing test and would only get 16 to 17 degrees advance with the engine at 2k to 2200.

Your timing is advancing to 16 to 17 BTDC or getting 16 to 17 more degrees of advance?

If your getting more then your good which equals 24 to 25 degrees total advance

 

[Doctom]

Put the ignition sensor in the distributor last night and started the boat on the trailer with the muffs.
It sounded a heck of a lot better so I but in the water this morning.
Step 1: Reved motor with boat still on trailer and then put in gear and Reved motor again. Boat responded beautifully.
Step 2: Totally unhooked boat from trailer and went for a short ride. Around 2k RPM 1st backfire through carb., thought it might be just running out some bugs so to speak. Then 2nd and 3rd backfire through carb. back to back after reapplying throttle.
At this point I turned back towards the dock, loaded boat back on the trailer and came home.
As to the timing question: The boat idles around 8 degrees BTDC. At 2k to 2200 RPM, it gets up to 16 to 17 degrees BTDC. So I am not seeing the All In total advance of 24 to 26 degrees BTDC.
What should be the next step?
I am thinking of rechecking/ resetting timing from base to start. Other than that I am at a loss.

 

[alldodge]

Backfire thru the carb at lower rpm is caused by a intake valve not fully closing or its firing while the valve is still open.
Valve could be open if:
The plug wires are in the wrong order
Plug wires are arching between each other
Distrbutor cap is cross arching inside
Cam and crankshaft are not timed

I don't see this being a timing thing unless its way off. The only way it could be way off is if the harmonic balancer slipped. Maybe if the timing chain slipped it can cause backfire, but why would it still have 150 psi compression

If timing was at (lets say) 15 BTDC it still would not backfire thru the carb, it would have a pre-ignition ping.

Remove the port side valve cover, number 1 spark plug and distributor cap, then rotate the motor around to where the balancer and rotor are at TDC.
Note:
Did intake valve close a good ways before the balancer mark came up?
Is the piston full up at TDC?
Is distributor pointing at number 1?

 

[Doctom]

Sorry for taking so long between updates. I work a lot and have very little down time, in which I Love to fish and preferably on my boat. But I digress.

To answer the above questions:

Did intake valve close a good ways before the balancer mark came up? Yes, pretty much all of the way closed.

Is the piston full up at TDC? Yes, I held my finger over the number 1 plug hole untill it was done farting air out and JUST STARTED to suck air in.

Is distributor pointing at number 1? Yes

I am also wandering What could or would stop full on timing advance?

Thank You All for your help and knowledge

 

[alldodge]

Like brand new compression numbers
TB-5 ignition which starts good, idles fine
Carb rebuilt and even with another carb same issue

Fuel Pressure: 3 to 4 running

The mechanics of your boat is near perfect yet you have issues. I wish I could provide more possibilities but with a perfect running motor. There is no reason for a backfire unless its running lean, but the carb is perfect, i don't know where to start and I'm out of ideas