No power under load....

[b.gagnon]

1989 Mercury(Sea Ray) V6 135hp
Serial # C110747
Running a 17p stainless prop on a 17' 2260lb sea ray
New to me boat + Motor so I have little history on it. The previous owner said it took a very long time to warm up!

It has no power above 2500-3000RPM. After 10-15 minute warm up it will have some power but it takes a minute or so to get on plane, then only hits 4500-4800rpm trimmed way up.
Other than that it runs and idles great. Starts right up and the primer bulb stays hard at any rpm. My last trip out I hit the throttle and it jumped up and hit 5600 rpm with no problem just that one time after 30 minutes of warm up.
I tried hitting the primer while under way and it had no effect. I was hoping that it would be a fuel problem but am now leaning to expensive electrical components!
I believe that all the electrical is original on this motor. The Tach is also bouncing here and there so I hope the $700 voltage regulator is ok....Charges at aprox 13v at idle and 14.5-15 above a few k rpm.

List of things I have done
T-stats changed runs 145 -160f
Cleaned carbs (no soak) new gaskets.
Rebuilt fuel pump (old one was a mess , was original to 1989)
Tested trigger (ok)
Stator test (ohm test ok) I need to get a DVA....
I need to test the coils next.
Checked spark in the driveway and they seem to all fire.
Compression is 120 +-3 on all cyls.
Timing was near 11 at idle and 17 at wot..(Very bright out but somewhere in that range)

All electrical testing was done quickly and I need to do it again when I have some time!

Thanks!

 

[JB]

Re: No power under load....

Did you test to see if all cylinders are making power? At idle, pull each spark plug lead (carefully!) and note difference in rpm. No change means not making power.

 

[Chris1956]

Re: No power under load....

What shape is the poppit valve? That could be issue with warm up.

 

[b.gagnon]

Re: No power under load....

I did pull the plugs one at a time (on muffs) and there was almost no noticeable difference between any of the cyls.(no change) It was like the engine did not care about missing a plug... This was done before I cleaned the carbs so I will do it again. Originally the bottom carb had a float stuck and was leaking out the front.
I have not checked the popit valve. Usually within 2-3 minutes the t-stats open at 145f and will stay there.

 

[b.gagnon]

Re: No power under load....

I Hooked up my timing light and #1 #5 not firing! (this time it was not running well and smoking a lot)..
I swapped the coils and they both fired then I put them back and #1 stayed firing and #5 did not. In all the moving around I proved that the coils are good. Switchbox????
When I checked for spark last week I thought that my mind was playing tricks by seeing and not seeing spark.. Now I think it fires when it wants to...

 

[b.gagnon]

Re: No power under load....

I just put two new switchboxes in, and it is firing on all cylinders. I wont know if it solves my problem until I have time to take it to the water. I am still getting a bounce in the Tach every now and then (hope I dont need a voltage regulator)....

 

[wired247]

Re: No power under load....

$700 voltage regulator? Forget that. Get rid of the water cooled regulator. It was a bad gimmick that didnt work well anyway. Replace the exhaust chest cover with a later model unit and buy one of the $60 regulator/rectifiers from a 40 amp system. Everything hooks right up . You are out less than $100 and you have a better more reliable system. If you cant find a chest cover I'll give you one.

OR just leave the old regulator where it is and use one of the newer stye instead mounted over it. You still have plenty of clearance back there. If you have a 40 amp system system use two of the 20 amp regulators. Still out less than $130

 

[b.gagnon]

Re: No power under load....

I took it out today and it was running great 5600rpm with me and two other people! One problem is that at full speed it was running
hot(180-200f). At one point it shot back down to 145 very quickly.. I'm thinking gauge or popit valve? I will install an impeller in the spring no matter what because I have no idea when it was last replaced. I probably will winterize it soon the water was 45f and the wind was cold as hell! Next I have to fix the warning system, it does nothing when i turn the key. last time I took it out it sounded when I turned the key on for a few starts but before and after that it has not worked. Thinking it may be a bad ground.