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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15875
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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2005 Reinell 5.0 305 motor with throttle body ignition. At

Customer Question

2005 Reinell 5.0 305 motor with throttle body ignition. At low Rpm misfires and blows black smoke, at high rpms runs good.
Submitted: 2 years ago.
Category: Boat
Expert:  Jason replied 2 years ago.
Hello my name is ***** ***** am I speaking with?
Is this a Mercruiser or Volvo engine? (or something else)? Do you have a model or serial number on it?
When did this problem start?
Customer: replied 2 years ago.
Customer: replied 2 years ago.
Problem started 6/9/15
Expert:  Jason replied 2 years ago.
Is it fuel injected or carbureted? Do you have the actual model number on it?
Customer: replied 2 years ago.
Throttle body ignition and my name is scott
Expert:  Jason replied 2 years ago.
Hi Scott. Black smoke is caused by 2 things.
1, an extremely rich fuel condition.
2, low engine compression
305's like to eat valves. They are known for doing so. I would suspect you have 1 or more cylinders with bad valves in it. The engine would need a compression test next to confirm that. Is that something you are able to do?
Customer: replied 2 years ago.
I don't think it's a valve because it runs great at 3500rpm and higher. If it was a valve wouldn't it run bad at high RPM also.
Expert:  Jason replied 2 years ago.
If it was a valve wouldn't it run bad at high RPM also
No, not necessarily. If the engine has 7 cylinder with perfect compression and just 1 with low compression due to a bad valve issue it will still run good at higher rpms.
There are a couple of ways to isolate which cylinder might be the bad one if you don't want to compression test the entire engine, and that is to do a cylinder drop test. What is done here is with the engine running, you would use a pair of insulated pliers and pull each spark plug wire off the distributor cap one at a time (and then putting it back) and seeing which one causes the misfire to stop. For example, pull #1, if the misfire is still there put it back and then pull #2, and then follow it all the way around. Does that make sense?
Expert:  Jason replied 2 years ago.
Are these tests that you are able to do on your own, or were you just trying to get an idea of what you might be in for before calling in the mechanic?
Customer: replied 2 years ago.
That makes since so I'll do a compression test first and if my compression is good then my next step would be injectors
Expert:  Jason replied 2 years ago.
If compression is good then the next step is actually checking fuel pressure. If the pressure regulator is bad fuel pressure will be to high, and that would cause the injectors to spray to much fuel, again causing that extremely rich fuel condition. Now if fuel pressure ends up being good then the next step would be looking to see if any of the injectors are stuck open.
I don't know how you want to leave this. But that is where you stand on your end and what needs to be done.I do want to make sure you are happy with the service I am providing to you before you go. Did you have any other questions on the engine or do you think that covers it? -Jason
Expert:  Jason replied 2 years ago.
Just incase you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. Please let me know if you run into any problems or errors when trying to do it. Questions do not lose out, so if you have to come back tomorrow or next with follow up questions to this you still can even after doing a rating
If I do not hear back from you I thank you in advance and good luck!
Expert:  Jason replied 2 years ago.
Hello, just checking in, any luck? -Jason

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