No power are full throttle

[thisuldoit]

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]

Re: No power are full throttle

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

 

[thisuldoit]

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]

Re: No power are full throttle

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]

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]

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]

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]

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!

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

 

[thisuldoit]

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]

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]

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]

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]

Re: No power are full throttle

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

 

[thisuldoit]

Re: No power are full throttle

I will try all of that this afternoon.

Thanks!!!

 

[WAVENBYE2]

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]

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]

Re: No power are full throttle

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

 

[Gary H NC]

Re: No power are full throttle

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

 

[thisuldoit]

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]

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!