danac
Cadet
- Joined
- Jun 27, 2018
- Messages
- 7
Hello all - been lurking for a while and finally have some questions. I have a 1989 Mercruiser 5.7 stern drive with a
first gen alpha one. This is my first season with it and am still learning some of it's quirks but I feel like it is lacking performance. It starts easy, idles fine, runs ok up to 4K rpm then loses steam quickly and eventually makes some clacking sounds if you keep trying to push it past 7/8 throttle (which I don't). It cruises fine between 3-4K rpm although it consumes what I would consider a lot of fuel, sounds like it is laboring to me, and generates some soot on the outside of the transom. I have not been able to get the boat past 35mph (It's a 19' lake boat). I replaced all the "tune-up" type parts, plugs, cap, rotor, fuel filter, etc. and decided to check the timing which is where it got weird.
I don't have the serial number because the motor was replaced at some point but it has a Mercruiser 2bbl carb and TB4 ignition module stamped V8-22. What I appear to be seeing (and what I would like someone to verify that I am not misunderstanding) is that my timing advance curve does not look like I would expect it to after reading the manual. Long story short at 3400rpm when my timing should be all in at 30deg I am only seeing at most 20. The base timing could use a couple more deg at only 6 but I can't imagine that is the root of the issue. Am I missing something here? I have not read that the TB4 module generally fails in this way but if so would this explain the symptoms I described? The manual implies that the TB4 module alone controls the advance so I am assuming the dist is ok. I am going to order a timing tape for the
HB to make sure I am not reading this wrong but not quite sure where to go from there. I have attached several snapshots of videos I took with the timing light at various rpms. Thanks for any help you can offer!
Dana
first gen alpha one. This is my first season with it and am still learning some of it's quirks but I feel like it is lacking performance. It starts easy, idles fine, runs ok up to 4K rpm then loses steam quickly and eventually makes some clacking sounds if you keep trying to push it past 7/8 throttle (which I don't). It cruises fine between 3-4K rpm although it consumes what I would consider a lot of fuel, sounds like it is laboring to me, and generates some soot on the outside of the transom. I have not been able to get the boat past 35mph (It's a 19' lake boat). I replaced all the "tune-up" type parts, plugs, cap, rotor, fuel filter, etc. and decided to check the timing which is where it got weird.
I don't have the serial number because the motor was replaced at some point but it has a Mercruiser 2bbl carb and TB4 ignition module stamped V8-22. What I appear to be seeing (and what I would like someone to verify that I am not misunderstanding) is that my timing advance curve does not look like I would expect it to after reading the manual. Long story short at 3400rpm when my timing should be all in at 30deg I am only seeing at most 20. The base timing could use a couple more deg at only 6 but I can't imagine that is the root of the issue. Am I missing something here? I have not read that the TB4 module generally fails in this way but if so would this explain the symptoms I described? The manual implies that the TB4 module alone controls the advance so I am assuming the dist is ok. I am going to order a timing tape for the
HB to make sure I am not reading this wrong but not quite sure where to go from there. I have attached several snapshots of videos I took with the timing light at various rpms. Thanks for any help you can offer!
Dana
