3.0 Mercruiser Choking

[ImTheBiggerBoat]

97 capri, alpha 1. long day of running the boat last weekend. There are a couple of things I need sorted out. We have a good 10 minute no wake until open water, when I get to punch the throttle it boggs down, I need to pull back on the throttle and ease into it then we get onto plane. Later in the day this is not an issue. Towards the end of the day of running the boat WOT (4,400-4,600) general cruising, gauges all normal, fueled up, the boat appears to choke out, similar symptoms or the “launch lurch”. Once before it bogged down the engine and turned off, last time I had to keep it around 20 mph and limp back to dock. Thoughts?

 

[achris]

Thoughts?

There's something wrong with your engine!

So, apart from '3 litre in a 1997 boat', what more can you tell us about this engine? (we don't care about the boat, just the engine. Boats and engines are 2 different manufacturers often not even the same year, just look at my boat!). Can you give us the serial number, the type of ignition (3 different types were used, points, EST and DDIS), and maybe some steps you've already taken to find the problem?

And looking at your photo, that's an Alpha One Gen II, and the trim tab anode is missing!

Chris.....
(never heard of 'launch lurch', you'll need to explain that one)

 

[Scott Danforth]

what maintenance has been done?
new to you boat?
first suspect is the accelerator pump

 

[dubs283]

what maintenance has been done?

I'm with this. Need to establish a baseline here. Tune up performed? Fuel filters inspected/replaced? Fuel pressure/vacuum?

So many culprits could be associated with your issue, need to start eliminating them one by one

 

[achris]

what maintenance has been done?

The trim tab anode is missing. I suspect the answer is 'not a lot'...

 

[ImTheBiggerBoat]

There's something wrong with your engine!

So, apart from '3 litre in a 1997 boat', what more can you tell us about this engine? (we don't care about the boat, just the engine. Boats and engines are 2 different manufacturers often not even the same year, just look at my boat!). Can you give us the serial number, the type of ignition (3 different types were used, points, EST and DDIS), and maybe some steps you've already taken to find the problem?

And looking at your photo, that's an Alpha One Gen II, and the trim tab anode is missing!

Chris.....
(never heard of 'launch lurch', you'll need to explain that one)

The trim tab anode is missing. I suspect the answer is 'not a lot'...

New engine put in boat by Mercruiser certified dealer last summer. New accessories that were put on old motor transferred to new motor include alternator, fuel pump, fuel pick up line and anti-siphon valve, starter, head gasket, and basically the entire lower end overhaul including gimble bearing, trim senders, and all bellows. Boat was properly winterized at the end of last season including oil change. New lower lower end fluid last month. Yes the boat has been up on maintenance, but has a few kinks to work out, the genesis of this post the most relevant. New zincs were ordered and the trim anode was the wrong fit for the gen II. Need to get that in.
From what i'm reading this appears to be a starvation of fuel to the engine. I did my best to clean the fuel tank without removing it last fall (I.E, run an inline pump and filter in and out of it to catch most of the impurities and or deposits), but I can tell (visually) there is some contamination still in the tank from a previous life. I self performed a carb re-build last year as well. The only part of the re-build I wasn't 100% certain of was the float bracket adjustment, also unsure if this would create the situation I'm in now. @achris thanks for the help, sorry for taking so long to respond.

 

[ImTheBiggerBoat]

There's something wrong with your engine!

So, apart from '3 litre in a 1997 boat', what more can you tell us about this engine? (we don't care about the boat, just the engine. Boats and engines are 2 different manufacturers often not even the same year, just look at my boat!). Can you give us the serial number, the type of ignition (3 different types were used, points, EST and DDIS), and maybe some steps you've already taken to find the problem?

And looking at your photo, that's an Alpha One Gen II, and the trim tab anode is missing!

Chris.....
(never heard of 'launch lurch', you'll need to explain that one)

This was a stupid term I made up to categorize the issue I ran into throttling from "no wake" to planning where the engine would bog down.

 

[Scott06]

The only part of the re-build I wasn't 100% certain of was the float bracket adjustment, also unsure if this would create the situation I'm in now. @achris thanks for the help, sorry for taking so long to respond.

By not being sure of the float bracket adjustment I take that to mean the float level is not set correctly?

Yes if float level is off this could cause what you are observing. Also would look did you install any check balls in the accelerator pump circuit correctly?

If you disconnect the throttle cable and pump the throttle do you see two good streams of gas coming out of the accelerator pump nozzle? if not it will bog down on acceleration. Also check that the linkage on the accelerator pump is adjusted correctly and tight so there is no delay in the pump plunger going down when you hit the throttle. Yours may have several holes on the accelerator pump arm to create bigger or smaller pump shot - upper most hole is biggest shot can try that

 

[ImTheBiggerBoat]

By not being sure of the float bracket adjustment I take that to mean the float level is not set correctly?

Yes if float level is off this could cause what you are observing. Also would look did you install any check balls in the accelerator pump circuit correctly?

If you disconnect the throttle cable and pump the throttle do you see two good streams of gas coming out of the accelerator pump nozzle? if not it will bog down on acceleration. Also check that the linkage on the accelerator pump is adjusted correctly and tight so there is no delay in the pump plunger going down when you hit the throttle. Yours may have several holes on the accelerator pump arm to create bigger or smaller pump shot - upper most hole is biggest shot can try that

The rest of the instructions were very clear about the accelerator pump and check balls, should be fine. Not proud of not understanding the float adjustment, just be prepared to suffer the consequences. Thanks for the direction.

 

[Scott06]

The rest of the instructions were very clear about the accelerator pump and check balls, should be fine. Not proud of not understanding the float adjustment, just be prepared to suffer the consequences. Thanks for the direction.

Accelerator pump adjustment

Float adjustment this is a rochester. 2 jet but is done same as mercarb

 

[ImTheBiggerBoat]

Accelerator pump adjustment

Float adjustment this is a rochester. 2 jet but is done same as mercarb

Thank you very much for this.

I was out on the lake all day yesterday and the boat performed really really well all day. Probably 3 hours of run time. As stated before, the prominent issue surfaces towards the end of the day, the timing is very suspect. I've attached a video of the helm to show you exactly what i'm talking about. throttle control is kept at the location the entire time. if I try to accelerate, the "bogging" gets more pronounced". I keep going back to potential settlement in the fuel tank that gets stirred up throughout the day then sucked up causing this but I could be completely off base. I welcome all feedback.

 

[nola mike]

Th. I keep going back to potential settlement in the fuel tank that gets stirred up throughout the day then sucked up causing this but I could be completely off base. I welcome all feedback.

Certainly possible, but I'd expect it to surface earlier. Have you checked your fuel filter for gunk/water? Also, you can put a timing light on the plug wires to see if you're getting a consistent spark when this happens.

 

[Scott06]

In addition since it takes run time for problem to crop up maybe fuel tank vent is clogged putting tank under vacuum try opening the gas cap when it happens see if it makes a difference

 

[ImTheBiggerBoat]

In addition since it takes run time for problem to crop up maybe fuel tank vent is clogged putting tank under vacuum try opening the gas cap when it happens see if it makes a difference

This is something i've not seen discussed, great idea.

 

[ImTheBiggerBoat]

Certainly possible, but I'd expect it to surface earlier. Have you checked your fuel filter for gunk/water? Also, you can put a timing light on the plug wires to see if you're getting a consistent spark when this happens.

Definitely will look into it.

 

[dubs283]

This is something i've not seen discussed, great idea.

Post #4.....

 

[ImTheBiggerBoat]

Post #4.....

Tip of the hat, thank you

 

[ImTheBiggerBoat]

Removed the fuel vent line and vent, line clear, adjusted pitch, actual vent was absolutely caked with sludge and gunk. Solved the issue, thanks guys

 

[dubs283]

Removed the fuel vent line and vent, line clear, adjusted pitch, actual vent was absolutely caked with sludge and gunk. Solved the issue, thanks guys

Guessing by "adjusted pitch" you mean rerouted the vent line and cleaned the "sludge and gunk" out?

Glad your issue is resolved and would suggest if all the above is true you should replace the entire vent line with approved fuel rated hose and inspect/replace the other hoses/fuel lines related to the fuel supply system

 

[ImTheBiggerBoat]

Guessing by "adjusted pitch" you mean rerouted the vent line and cleaned the "sludge and gunk" out?

Glad your issue is resolved and would suggest if all the above is true you should replace the entire vent line with approved fuel rated hose and inspect/replace the other hoses/fuel lines related to the fuel supply system

This is the only fuel related line I haven’t replaced since owning, they’re in good shape and within spec. The vent line is original and rated. I removed one of the clamps on this line a year ago not realizing how important maintaining pitch on the line was when I reinstalled. Yes, cleaned out gunk. Again, thanks for bearing my inability to adequately diagnose myself. Never assume a level of intelligence, you all do a nice job keeping your cool.