1987 mercruiser 4.3L 205HP bogs down

[Orlando Len]

Besides loose steering my motor has issue too. It will not rev past 2K rpm's when on the water in gear. At first it did, say for 15/20 min it would run on plain and seemed OK. It had some breaking up at w.o.t. (4200 PRM) but other wise smooth cruising. Then I slowed to idle speed to attempt a water ski type whole shot and that when the problem started.
I can see the fuel inject down the carb when I pump the throttle hard so that works. Out of gear (no load) the motor shakes around pretty good when I advance the throttle beyond 2K RPM's (+ -).
I did just install a new fuel pump w/ filter assy. The old one was working, but it had fuel showing in the clear tube that leads to the carb.
Question when CDI ignition goes on this vintage motor is it heat related or sensitive? meaning after the motor reaches 145 deg it can start dropping cylinders?
Thank you, Len,

 

[180shabah]

Re: 1987 mercruiser 4.3L 205HP bogs down

A bad coil can do what you describe, but so can many many other things.

A good place for you to start is the "adults only" sticky at the top of the page. It is more than just a cute name.

 

[180shabah]

Re: 1987 mercruiser 4.3L 205HP bogs down

http://forums.iboats.com/showthread.php?t=288430

 

[Bondo]

Re: 1987 mercruiser 4.3L 205HP bogs down

Ayuh,...

Sounds like your Whole Driveline has a Lot of Problems going on,...

When was the last Full Tune-up,+ Service done,..??

 

[Chris1956]

Re: 1987 mercruiser 4.3L 205HP bogs down

Len, If the motor shakes around when you rev it a bit in neutral, it may be not runninng on all 6 cylinders. Check for coil arcing to ground, or spark plug wires arcing to ground. Inspect the spark plugs for color and wear. They should all be the same color and not have any wear(worn strap electrode or center electrode). I do not remember if that motor had a mechanical spark advance under the dissy cap, but take a look and see if the weights on the advance are there and if so, operate properly.

 

[Orlando Len]

Re: 1987 mercruiser 4.3L 205HP bogs down

Launched the boat again the other day, this time with a helper to drive while I tried a a few thing to the motor. Apparently the steering is worse then I think as my helper make several comments about it (different post). One problem at a time..
The symptom are bit different then the last post. At first the boat comes up on plain with some fussing around of the motor (some missing going on for sure). The tach acts up when the motor reaches about 3 k rpm and as the throttle advances it drops 1000 RMS +- although the motor is speeding up still. The motor run worse the faster I attempt to make it go and I figure it's not turning more the 3200/3300 rmps. Keeps on plain and I can find a sweet spot where the engine smooths out and w cruise along nicely.
After a few laps around Lake Underarm (Under hill) say 15 minutes we stop and restart, now I can no longer get on plain. I see about 2k RPM on the tach and the motor struggles.
I about emptied an inverted can of Duster on the coil and thunderbolt ignition pack in an attempt to cool thing off before attempting to get the boat on plain but this had no effect. I also attempted to slosh a bit of gas down the carb while attempting to plain to see if it was staving for fuel, This also this had no effect. A bit on the risky side and I know I'm gonna hear about that. I got away with it and the hair on my arm still.
I feel I need a Thunderbolt Ignition pack. Any thoughts to add?

 

[JustJason]

Re: 1987 mercruiser 4.3L 205HP bogs down

I feel I need a Thunderbolt Ignition pack. Any thoughts to add?

I feel you need to do some troubleshooting instead of guessing.
Go to the Adults only section and find the manual for your engine.

I'd start with a full tune up including all fuel filters. Then i'd be checking my timing. Then i'd be checking my fuel supply from the boat to the engine.....

 

[Bondo]

Re: 1987 mercruiser 4.3L 205HP bogs down

I feel I need a Thunderbolt Ignition pack. Any thoughts to add?

Ayuh,... If it Did,.. It wouldn't run at All....

I asked this Before,..??
"When was the last Full Tune-up,+ Service done,..??"

Like Jason says,...
Why don't you do the Diagnostics,..??