hard starting after tune-up kit and timing adjustment

[luckyluke]

Just got my boat back from the shop and wonder if timing is out.

I brought the boat to the shop because the engine was cutting out temporarily or missing under load and I thought it was starving for fuel. It sort of behaved that way. It would bog down, catch up then cut out again. I could only run at about 1800 rpm.

Also, since I've owned the boat (little over a year) it has a dead spot on the throttle if you accelerate too quickly; it bogs than catches up. If you accelerate slowly, no problem

The mechanic I brought it to said he installed a tune up kit (points, rotor button, condenser etc.) and cleaned the carb. He said he advanced the timing as it was set too far back (retarded). He said this was a common problem for boat engines running in more northern climes.

When I went to pick it up he said "she works like a top now, better than ever."

That was Monday, I put the boat in the water today and had a really hard time getting it started. I pumped the throttle a few times before turning it over, let it crank for a few secs, wait and repeat. It probably took 6 to 10 tries before she finally lit up.

It finally started, and appears to run well, no miss or cutting out, but it still has a dead spot on accelerating.

Would timing too far advanced make an engine harder to start?

Thanks

 

[achris]

Re: hard starting after tune-up kit and timing adjustment

The usual cause of 'bogging on acceleration' is a clogged/faulty accelerator pump in the carb. Take the cover off the carb and have a look down the hole. With the engine NOT running, have someone push the throttle lever to full. You should see 2 nice healthy squirts of fuel being shot down the barrels. No fuel, time to pull the carb off and clean it properly. Just giving it a clean on the outside does nothing for the passages or float chamber.

As for the hard starting, check the points are opening properly. Use a feeler gauge and make sure they are about 22 thou. I would also run a piece of newspaper between them to get any glaze off.... You could also check the timing (I would) if you have a timing light. If you don't and think it's something you might be doing in the future, a cheap one will suffice for your needs... Something like THIS would do just fine.

Do you have a genuine manual for your engine?

Chris.........

 

[luckyluke]

Re: hard starting after tune-up kit and timing adjustment

Thanks, I kind of suspected the accelerator pump myself. My mechanic just said it could be a week fuel pump. I'm starting to have my doubts about him.... I'll check the accelerator pump action myself tomorrow. The engine works fine at WOT.

The points are new this week so I hope they're not glazed. I'll check clearances as you suggested.

I've found a link to an on-line version of the manual; thanks.

Luc

The usual cause of 'bogging on acceleration' is a clogged/faulty accelerator pump in the carb. Take the cover off the carb and have a look down the hole. With the engine NOT running, have someone push the throttle lever to full. You should see 2 nice healthy squirts of fuel being shot down the barrels. No fuel, time to pull the carb off and clean it properly. Just giving it a clean on the outside does nothing for the passages or float chamber.

As for the hard starting, check the points are opening properly. Use a feeler gauge and make sure they are about 22 thou. I would also run a piece of newspaper between them to get any glaze off.... You could also check the timing (I would) if you have a timing light. If you don't and think it's something you might be doing in the future, a cheap one will suffice for your needs... Something like THIS would do just fine.

Do you have a genuine manual for your engine?

Chris.........

 

[NHGuy]

Re: hard starting after tune-up kit and timing adjustment

It also would be good to look at the choke before you start it up. It should be closed. Some chokes don't close til you pump the gas, so give it two or three pumps to see if it closes.

 

[luckyluke]

Re: hard starting after tune-up kit and timing adjustment

Thanks, will check that as well.

It also would be good to look at the choke before you start it up. It should be closed. Some chokes don't close til you pump the gas, so give it two or three pumps to see if it closes.

 

[achris]

Re: hard starting after tune-up kit and timing adjustment

Thanks, I kind of suspected the accelerator pump myself. My mechanic just said it could be a week fuel pump. I'm starting to have my doubts about him.... I'll check the accelerator pump action myself tomorrow. The engine works fine at WOT.

The points are new this week so I hope they're not glazed. I'll check clearances as you suggested.

I've found a link to an on-line version of the manual; thanks.

Luc

Couple of things I'll comment on.

1. New points MUST be cleaned before using them. Part of the manufacturing process is to coat the contact surfaces so they don't corrode before they get sold, and that coating needs to be removed....

2. 'On-line' manual... Which species? If it's clymer :facepalm:, I'll post a link to the genuine manual for you....

Chris.......

 

[luckyluke]

Re: hard starting after tune-up kit and timing adjustment

This is what I've been using...... Boatinfo - Mercruiser Service Manual nr. 8 - 1985-1989 - Mercury Marine 4 Cylinder Engines

Couple of things I'll comment on.

1. New points MUST be cleaned before using them. Part of the manufacturing process is to coat the contact surfaces so they don't corrode before they get sold, and that coating needs to be removed....

2. 'On-line' manual... Which species? If it's clymer :facepalm:, I'll post a link to the genuine manual for you....

Chris.......

 

[achris]

Re: hard starting after tune-up kit and timing adjustment

This is what I've been using...... Boatinfo - Mercruiser Service Manual nr. 8 - 1985-1989 - Mercury Marine 4 Cylinder Engines

That's the factory manual.... Good choice... :thumb:

 

[Volphin]

Re: hard starting after tune-up kit and timing adjustment

I agree with Chris, this sounds very carb related. Why not just treat her to a full carb rebuild. It's not that hard and it has to come off anyway..

 

[luckyluke]

Re: hard starting after tune-up kit and timing adjustment

I agree with you all. Just went on the boat to check suggested items out.

First, checked to see if pumping throttle prior to start would squirt fuel into carb: Yes

Second, checked to see choke position, it was open even after a couple of pumps but when I flicked it with my finger, it closed to a half open position.

Third, turned the key and she fired right up first shot. Warmed her up and idles well.

Went for a 45 minute run. Still has a bog when I punch it from zero, not at all if I accelerate slowly (which is what I normally do anyway).

When I push it to WOT I hear a little rattling noise I didn't have before tune-up. Kind of sounds like valves or rockers. Again, only at WOT and if I back off it stops. Could this be timing?

The boat ran well but when I got back home, she wouldn't idle, she stalled when in neutral.

Bottom line, I think I need timing checked and carb kit. I really do appreciate the input I receive from everyone on this forum.

Thank-you,

Luke

I agree with Chris, this sounds very carb related. Why not just treat her to a full carb rebuild. It's not that hard and it has to come off anyway..

 

[Bondo]

Re: hard starting after tune-up kit and timing adjustment

I agree with you all. Just went on the boat to check suggested items out.

First, checked to see if pumping throttle prior to start would squirt fuel into carb: Yes

Second, checked to see choke position, it was open even after a couple of pumps but when I flicked it with my finger, it closed to a half open position.

Third, turned the key and she fired right up first shot. Warmed her up and idles well.

Went for a 45 minute run. Still has a bog when I punch it from zero, not at all if I accelerate slowly (which is what I normally do anyway).

When I push it to WOT I hear a little rattling noise I didn't have before tune-up. Kind of sounds like valves or rockers. Again, only at WOT and if I back off it stops. Could this be timing?

The boat ran well but when I got back home, she wouldn't idle, she stalled when in neutral.

Bottom line, I think I need timing checked and carb kit. I really do appreciate the input I receive from everyone on this forum.

Thank-you,

Luke

Ayuh,.... It takes atleast 1 stroke to Wot to set the choke for a cold start,...

That's Detonation, yer motor eatin' itself alive, it could be timin', or a Lean condition,...

 

[luckyluke]

Re: hard starting after tune-up kit and timing adjustment

Ayuh,.... It takes atleast 1 stroke to Wot to set the choke for a cold start,...

That's Detonation, yer motor eatin' itself alive, it could be timin', or a Lean condition,...

SCARRY! Thanks for the heads up! He did say he advanced the timing, so likely, too much.

 

[Eric 3.7LX Alpha 1]

Re: hard starting after tune-up kit and timing adjustment

What engine are you referring to here..... the 470 in your signature?

Man I hope not. Do yourself a favor and get a timing light. A points system tune up is basic mechanics and something you should learn to do as a boat owner and captain. To know how the system works will pay off if you ever have trouble while on the water.

Here is a Mercruiser TSB for the 470 which talks about Retarding the timing BACK to 4? from 8?.

 

[Eric 3.7LX Alpha 1]

Re: hard starting after tune-up kit and timing adjustment

Have a look at the Sticky at the beginning of this forum:

How points ignition system works:
http://forums.iboats.com/mercruiser...ignition-system-works-329742.html#post2186518

How To: Tune-up Your Engine with Points Ignition
http://forums.iboats.com/mercruiser...ne-up-your-engine-points-ignition-335302.html


those are just two from there^^^ there's tons more info

 

[ewpvic]

Re: hard starting after tune-up kit and timing adjustment

What engine are you referring to here..... the 470 in your signature?

Man I hope not. Do yourself a favor and get a timing light. A points system tune up is basic mechanics and something you should learn to do as a boat owner and captain. To know how the system works will pay off if you ever have trouble while on the water.

Here is a Mercruiser TSB for the 470 which talks about Retarding the timing BACK to 4? from 8?.

I agree with Eric and Bondo. Once I had dwell and timing advance within the acceptable range (all the way to WOT). The noise that I had (detonation) disappeared. That kind of engine damage makes for a short game. The old 3.7 runs like a top all the way through rpms.

Good luck.

 

[luckyluke]

Re: hard starting after tune-up kit and timing adjustment

Update....

Changed the plugs, checked the points gap, and timing. The points gap was way to small; set to 0.022 in as per spec. The timing was advanced way beyond the 10 deg mark at idle; if I had to guess, it would have been about 35 deg.

Retarded the timing down to about 6 or 7 deg advance.

Now it idles really rough and if I give it throttle too quickly it stumbles. It idled better before I adjusted the timing.

Where do I go from here? Carb?

 

[achris]

Re: hard starting after tune-up kit and timing adjustment

Check that the harmonic balance hasn't slipped and is now showing the wrong timing, even though the timing marks look right...

 

[luckyluke]

Re: hard starting after tune-up kit and timing adjustment

Check that the harmonic balance hasn't slipped and is now showing the wrong timing, even though the timing marks look right...

Thanks, how do I do that?

 

[Eric 3.7LX Alpha 1]

Re: hard starting after tune-up kit and timing adjustment

Bring the number one piston up to top dead center and see where the mark is on the harmonic damper.

It should be at 0?

Here is a neat little trick to finding TDC: (The Eric in the video is not the same one that just posted it :lol

 

[Eric 3.7LX Alpha 1]

Re: hard starting after tune-up kit and timing adjustment

Here is a different way to check it using a piston stop tool in the spark plug hole: you can get a stop tool from most auto stores and speed shops for under 20 bucks. Auto Zone might even loan them out for free.