No power are full throttle

thisuldoit · Jun 28, 2007

I have an 89 Mercruiser I/O, 4.3L, Thunderbolt Ignition, 262 CID, 6 cylinder. I have recenlty rebuilt the carburtor, replaced the plugs, wires, and distributor. When I would start it at home on the muffs, it would start up, the idle is rough, but in throttle only it would run smooth and had the proper RPM's as I increased the throttle. I took it down to the river yesterday and while under load it would not go over 5 mph at full throttle.

Thoughts?

Haut Medoc · Jun 28, 2007

Re: No power are full throttle

How many rpm's at full throttle, in the water?......

thisuldoit · Jun 28, 2007

Re: No power are full throttle

I believe it was reading around 2.5K to 3K, but I unfortunatley did not pay attention as well as I should as a storm was coming up and yada, yada, yada. There was definitley power when I hit the throttle, just no speed.

Haut Medoc · Jun 28, 2007

Re: No power are full throttle

thisuldoit said:
I have an 89 Mercruiser I/O, 4.3L, Thunderbolt Ignition, 262 CID, 6 cylinder. I have recenlty rebuilt the carburtor, replaced the plugs, wires, and distributor. When I would start it at home on the muffs, it would start up, the idle is rough, but in throttle only it would run smooth and had the proper RPM's as I increased the throttle. I took it down to the river yesterday and while under load it would not go over 5 mph at full throttle.

Thoughts?

What kind of distributer?
Marine I hope........
Rpm tests on dry land with no load are irrelevant.....
The engine is not doing any work.....
If it runs rough with no load, it will be a real dog when it does.....
Make sure that the plug wires are correct & that the timing is as well, for starters......
If you can only get 5mph out of 2500 rpms, then I would suggest that you put on your spare prop & see if you get better results......

paulrfrancisco · Jun 28, 2007

Re: No power are full throttle

Mmmm.. Sounds similar to a problem I had last year (and Don S nailed it) if you replaced the rotor, count the metal fingers on the rotor, there should be 6 fingers on yours. if there are 8, then iit s the wrong one. I actually had the reverse happen to me with very similar symptoms I had a V8, with a V6 rotor installed.. Wrong part from the mfg in the box (actually I had twin engines, and received 2 incorrect rotors) so the reverse would certainly be plausable.

thisuldoit · Jun 28, 2007

Re: No power are full throttle

I mean to say distributor cap not distributor. I will check the timing again. Is there any way to set up a test tank, as I am at least an hour from the water.

Thanks!

paulrfrancisco · Jun 28, 2007

Re: No power are full throttle

Yes, all you need is a garden hose connected to a set of ear muffs... (go to a boating supply store and buy a set of muffs, you'll use them all the time.)

Just aask and they'll give you what you need.

Haut Medoc · Jun 28, 2007

Re: No power are full throttle

thisuldoit said:
I mean to say distributor cap not distributor. I will check the timing again. Is there any way to set up a test tank, as I am at least an hour from the water.

Thanks!

Not really.....
Check your wires & timing....

thisuldoit · Jun 28, 2007

Re: No power are full throttle

I have the muffs, but I was told that you cannot go over 1800 RPMs with them as, it would most likely collaspe the hose.

Second, I am guessing I check the timing while at idle, and advance timing with the boat in gear and under load? I have been checking the advance timing with the throttle only.

Haut Medoc · Jun 28, 2007

Re: No power are full throttle

It depends entirely upon your hose, if is stout enough, it will not be a problem at any rpm.......
Timing should be checked at idle.....
You do not need load to check advance timing....

thisuldoit · Jun 28, 2007

Re: No power are full throttle

Sounds good. Now, is there anything besides the timing that could be the issue. I have replaced all of the spark plugs and have new wires. I rebuilt the carburetor, and is there something in there that could be causing an issue?

Haut Medoc · Jun 28, 2007

Re: No power are full throttle

Did you change the water separating fuel filter?.....
A compression test would not be a bad thing either, to rule out any bad valve issues......
Since you pulled the plugs & saw no water, I assume that your mans/risers are OK.....
A vacuum tests might shed some light as well......

paulrfrancisco · Jun 28, 2007

Re: No power are full throttle

The rotor as I mentioned before.. or otherwise all the ignition peices.

thisuldoit · Jun 28, 2007

Re: No power are full throttle

I will try all of that this afternoon.

Thanks!!!

WAVENBYE2 · Jun 28, 2007

Re: No power are full throttle

If you don't mind me asking, What did you set your plug gap at? The reason I am asking is when I did mine I set them at .35, engine pured. so then I read they should be at .40, so I took them back out and set them at that .40 ran like S@#$, took em back out and put back at .35 and she purred again. ours is also 91 4.3L V-6 2bbl mercarb w/Alpha one. Oh ya HAUT the wrong gap was from SELOC man...

Maclin · Jun 28, 2007

Re: No power are full throttle

A wider gap at the spark plug can cause the "gaps" in the rest of the system to show up. Too wide of a plug gap and the cap can allow crossfire. Also poor condition plug wires will be stressed more. To take advantage of a wider gap all components must be in tip top condition (wires & boots, cap, rotor, points, etc....). Usually points systems can't do more than .035 gap, it can actually affect the timing.

thisuldoit · Jun 28, 2007

Re: No power are full throttle

The plug gap is at .35 as per manual specifications.

Gary H NC · Jun 28, 2007

Re: No power are full throttle

Compression test for sure! I got a feeling it will show the problem.

thisuldoit · Jul 4, 2007

Re: No power are full throttle

Ok, I checked the timing and I had it backwards. It was around 8 ATDC instead of 8 BTDC. With the boat in gear (throttle only) and at idle, I am now right at 8 BTDC, however, when I shift back to neutral the mark is jumping between 12, 8, and 4 BTDC and the engine is running somewhat irregular. I recenltly rebuilt the carburetor, so is this an idle mixture adjustment problem?

Thanks and happy 4th of July.

thisuldoit · Jul 4, 2007

Re: No power are full throttle

I am having computer trouble with the forum, so I am not sure the previous post made it. Please read the previous post to see my problem.

Thanks!

No power are full throttle

Petty Officer 2nd Class

Supreme Mariner

Petty Officer 2nd Class

Supreme Mariner

Petty Officer 1st Class

Petty Officer 2nd Class

Petty Officer 1st Class

Supreme Mariner

Petty Officer 2nd Class

Supreme Mariner

Petty Officer 2nd Class

Supreme Mariner

Petty Officer 1st Class

Petty Officer 2nd Class

Lieutenant Commander

Admiral

Petty Officer 2nd Class

Fleet Admiral

Petty Officer 2nd Class

Petty Officer 2nd Class