mercruzer stalls when trolling on wrllcraft steplift

[bowman103]

hello bought a 79 steplift well craft with a 305 198 hp motor runs great tried tolling with first time started to stall after an hour
cleaned with sea foam changed filters and plugs took out second time ran exhalant till tried trolling had same problem bogs down and stalls when trolling restarts every time but love to troll would like any advice to start with boat was only run for a hour this year the gentlemen that I bought from was original owner rack stored very well taken care of had hip replacement and 71 couldn't handle boat any more changed points to electronic there was fuel in boat 20 gal of gas when purchased boat forgot to ask how long was in tank for any advice to start with would be appreciated thanks

 

[achris]

Re: mercruzer stalls when trolling on wrllcraft steplift

In these cases, I start right from the beginning. Get yourself a baseline of engine condition and go from there.

Standard troubleshooting for an engine.

Engines require certain things to operate properly... Basically they need the correct fuel/air mixture to be compressed and then fired at the right time.

So, in this order.

1. Compression tests.
2. Check spark plugs, replace if needed.
3. If points, replace, along with condenser and rotor. Check and adjust, if needed, points cam dwell angle.
4. Inspect distributor cap, rotor and leads, replace if necessary.
5. Check spark quality (needs to be a nice BLUE spark drawn over 1/2").
6. Set timing. Check timing advance is working correctly.
7. Check/change fuel filters and check that the fuel system is not sucking air.
8. Check fuel pump pressure.
9. Check for full opening of the carb. Also ensure choke is opening fully when the engine is warm.

When all of these items have been done, THEN move to the fuel system....

I realise #3 doesn't apply to you... This is a standard 'copy and paste' I use all the time.. Saves time and typing...

Chris.....

 

[Maclin]

Re: mercruzer stalls when trolling on wrllcraft steplift

Take a look at the condition of the sparkplugs, that may reveal an over-rich fuel mix condition. If they are black and sooty then the engine is loading up when idling for that long and eventually gags. Restarting with the throttle open clears it enough to start again, but if this is the problem then the engine may need to run at higher rpm for a while to clear the plugs before getting another hour or so of idling before gagging again. Electronic ignitions can usually help the sparkplugs keep up with the over-rich mix but only for so long before symptoms of over-rich emerge.

I would give my engine a Medal if it could idle for that long and not overheat or load up That is one of the hardest things for a carbed engine to do (idle for hours at a time). I would look into an electric trolling setup with separate and extra batteries. That is more cost but your engine will thank you. A gasoline kicker is another option but obviously more cost involved.

 

[Bondo]

Re: mercruzer stalls when trolling on wrllcraft steplift

Take a look at the condition of the sparkplugs, that may reveal an over-rich fuel mix condition. If they are black and sooty then the engine is loading up when idling for that long and eventually gags. Restarting with the throttle open clears it enough to start again, but if this is the problem then the engine may need to run at higher rpm for a while to clear the plugs before getting another hour or so of idling before gagging again. Electronic ignitions can usually help the sparkplugs keep up with the over-rich mix but only for so long before symptoms of over-rich emerge.

I would give my engine a Medal if it could idle for that long and not overheat or load up That is one of the hardest things for a carbed engine to do (idle for hours at a time). I would look into an electric trolling setup with separate and extra batteries. That is more cost but your engine will thank you. A gasoline kicker is another option but obviously more cost involved.

Ayuh,.... While I'm agreein' with yer diagnosis, I'm questionin' yer repair options,...

Why screw with a perfectly good runnin' Ignition, when ya got a Carb problem,...

My barge will idle for Days on end, 'cause I Tuned the carb to provide the Right amounts of fuel, at All rpms,...

bowman103,.... Welcome Aboard,...

After you've done the Testin' that Chris mentions, I'm guessin' yer carb needs Rebuildin', 'n a good Tunin',...

 

[Maclin]

Re: mercruzer stalls when trolling on wrllcraft steplift

I agree with some carb tuning being in order, the sparkplugs will be the best indicator of an over-rich condition that needs to be corrected. That may be, and probably is, all that is needed. Keeping a points system in tune is also important for good clean burn in idling conditions. I encourage the OP to pursue the tuning aspect for the solution first.

To the OP, I mentioned the separate trolling motor not so much as a solution in place of any needed engine tuning, but more for enhancing the fishing experience regarding slow trolling speed navigation.

I have a 20 minute idle no wake zone I need to navigate at one spot we boat at, I have never had any issues but still appreciate what the engine had to go thru so to speak. Metaphorically speaking I guess I am kind of like an ex-Waiter that gives really good tips, having experienced the "bad" as well! I am also a bit of a pessimist and seem to expect problems, and when nothing bad happens I over compensate on the Kudos maybe... :first:

 

[Walt T]

Re: mercruzer stalls when trolling on wrllcraft steplift

Maclin is right, it's a very common issue. Bondo is right also, but not everyone is able to tune a carburetor properly like that, and I mean a lot of so called "Marine Techs" by that also. Truth is tuning carburetors is becoming a lost art. Guys (and women) who know what they're doing carburetor wise are becoming scarce. I remember the old multi carburetor set ups on a lot of cars. The famous 440 six pack was cool, MG had twin draft carburetors that were a challenge to keep tuned together. Most fun I ever had though was a customers Jaguar XJ-12 back when Jesus was a lad. Six carburetors on a V-12 that had to be tuned and had to be tuned correctly. I had a learning curve on that one. I used to take that .... THING for test drives and holy guacamole that mudda could accelerate. It wasnt until 2009 that I experienced that G force in a drivers seat again. (Excluding motorcycles) 440 six pack had nothing on that Jag.

But I digress

Free and easy.... do it Maclins way by pausing occasionally to rev it up to 1500-2000 rpms for 30 seconds or so. You can learn how to adjust idle mixture screws too, but it's possible to cause other problems by messing with them.

 

[CharlieB]

Re: mercruzer stalls when trolling on wrllcraft steplift

A decent low speed tach and a vacuum gauge and idle mixtures are a whiz on a 4 stroke. Adjust to highest idle speed and vacuum while in gear. I like to add 1/16 to 1/8 turn fatter just to make sure it never goes the slightest lean. Boat should troll for days without so much as a hiccup.