'73 Volvo Penta AQ170 wants to stall when first shifted into gear (for or rev)

[gibbstobyj]

First off, THANK YOU for being available and being a great information source for me leading up to our purchase. Nearly every Google search included an iBoats result that was useful! The boat we ended up purchasing is a 1973 Glastron Swinger V187 with a Volvo Penta AQ170. Boat and trailer are in great shape and the engine (if the hour meter is to be trusted) only has 594 hours on it.

As is the right of passage into boat ownership I discovered some issues that need at least some tweaking. Before I get to that, here are the compression measures in case they factor into anything (front to back): 105, 105, 80, 75, 90, 120. I know I’ve got issues there too, but they seem to get the job done for now and don’t seem to pose any imminent failures. I may be on here in a few months as Fall approaches and I prepare to dig into those.

On to my more pressing issues:
Whether cold or at operating temp, it will idle in neutral fine, but when I first drop in into gear (forward or reverse), that initial load wants to cause the motor to stall. If I get on the accelerator quickly to get past idle it’s good and will then run fine, but that’s not the way I want to have to operate, especially around the launch and other boats. When it’s cold, it seems it will always start back up. However, when it’s at operating temp the motor will crank but there’s no sign that it’s going to fire. Last weekend I was stranded for about 40 minutes before I was able to get it fired up, after which it ran fine again.

2 questions:

1. What are your thoughts on the issue(s) causing it to want to stall under that initial load/fuel demand? Fuel supply, vacuum, timing, other?
2. What’s the issue(s) causing it to not want to fire when it’s warmed up?

Thanks in advance, folks!

Toby

 

[bigkahuna427]

Just my thoughts.

If you checked compression before you bought the boat and it had not been run you should check again after it has been run. After sitting an engine can have some carbon floating around that will get stuck on valves and maybe a little corrosion. Not that compression is your issue.

If an engine does not start check spark, fuel, compression. This engine does not have a timing belt and you know you do have compression. So it is spark and fuel. I wonder if your engine may be flooding? Does it run rough at idle? If so you would pull the plugs. If they are wet and black then you have a fuel system problem.

In the event the no start and stalling are not the same issue I believe you have three separate carbs there. Linkages and balancing those should be done by someone familiar with doing that. If yourself or a prior owner started turning screws on the carbs which is commonly done it may need some adjustments.

I hope this helps!

 

[gibbstobyj]

Thanks bigkahuna. I don't have much experience to tell me what a "rough" idle is, but maybe you can tell from this video: https://drive.google.com/file/d/0Bwwc_QL0XB--eVBINlM4aTYyTXc/edit?usp=sharing
I pulled the plugs and they looked a bit charcoal in color. That tells me maybe too much fuel? I also noticed that the gaps are all over the place. Probably 50% difference from smallest to largest. Couldn't find my gap gauge so I'll get one and set those correctly. I hear you about leaving the fuel adjustments to someone who knows. I could probably tinker and figure it out, but my time is worth something too. Let me know your thoughts after watching the video. Hopefully it's helpful. Thanks.

 

[gibbstobyj]

Here's a link to a brief video of the motor running. Not sure if you can hear what you need from the engine over the noise of the outdrive. I took this video a couple weeks ago. I can get a better one if you think it would help.
https://drive.google.com/file/d/0Bwwc_QL0XB--eVBINlM4aTYyTXc/edit?usp=sharing

 

[bigkahuna427]

A picture of the plugs would help. If it were running rich they would be black like coal. Really hard to diagnose things on line with just a symptom.

 

[gibbstobyj]

You can find 2 pics of the plugs here: https://drive.google.com/folderview?id=0Bwwc_QL0XB--Mld6dGZfbDdtNUU&usp=sharing
You can find a video of the motor in idle here: https://drive.google.com/file/d/0Bwwc_QL0XB--R3RDTU5odE43N3M/edit?usp=sharing

I clearly had some oil on the plugs when I pulled them, so I know I have an issue there. I'm hoping to get into that this fall/winter.

 

[aogmitch]

Check your points. Had same issue last year and started getting worse. Was believing it to be carb related. Turned out to be the point gap closing up. Reset points, and all was well again.

 

[gibbstobyj]

I will have to check those. From what I'm reading I think it's something I could handle. It does beg the question of points vs electronic. Any thoughts on that topic would be welcome.

 

[captmello]

I would do a complete tune up. New points, condenser, cap and rotor, plugs, fuel filter, etc. Set the points with a dwell meter, and adjust the timing. Once this has been done, if you still have idle issues, you can continue to try to diagnose. Electronic ignition is not necessary if you adjust the points properly.

 

[gibbstobyj]

I've been thinking the same captmello. What else would you put in the "etc" bucket?
Also, it's not really "idle" issues. It's seems to idle reliably in neutral. It's when i first shift it into gear at low throttle where I experience the stalling issue. If I get it some throttle soon enough, it will be ok.
Does that change any of your thoughts? I've been asking around and I'm hearing the same themes of points and fuel flow, so I think they need attention no matter what.

 

[captmello]

The etc bucket could be anything I couldn't think of at the time. Maybe new plug wires, maybe a new water impeller if yours is more than 2 years old, maybe a thermostat, or clean your flame arresters... Once you've got all the ignition parts installed and adjusted, get the Idle set using a shop tach, A dwell meter will most likely have a tachometer. Also remember that your carbs do not have chokes, so the motor is going to be cold blooded no matter how finely tuned you get it. Also, regarding the Idle speed, the specs for the idle speed are with the boat in gear in the water, so since your motor has a relatively high idle (900-1000rpm), I would set the engine to idle in neutral right around 1000-1050 rpm. The idle rpms will drop when the boat is in the water in gear and you can then check to see if it is then in the 900-1000rpm range. Do this at operating temp. In gear on muffs is not the same as in gear in the water.

 

[gibbstobyj]

I reset all the plug gaps a few days ago to ~.31 and had it out today. was a bear to start.
Then I'm pretty sure I spun my prop getting out of the weeds around the launch. I could slowly increase to about 1/4 throttle and then it was like the prop outdrive just dissengage and the engine rev'd. We'll see where that end up. I must have hit something too because there is a bend on each blade that was not there before.
All in all, this is shaping up to be a traditional first time boat owner experience!!!

 

[gibbstobyj]

I fine tackling these individually, but from a system perspective, is there a particular order that I should do these to make it easier to identify the root problem or to get incremental gains?

 

[captmello]

You can do these things in any order you wish, once at a time or a few at a time. Do them correctly and move on. Gains are nice, but that's not the point. You want to run at peak efficiency, No?