help with Q-jet stumble and maybe down on HP (6-20-08 up date)

[nailem]

Re: help with Q-jet stumble and maybe down on HP

Re: help with Q-jet stumble and maybe down on HP

i check the timing marks and they are good reset timing to about 8 1/2 BTDS and the stumble is more or less gone. still does it a little when cold but has been good hafter it warms up.

i still need to get a compresion gauge. but what about the fule pump guage, is it the right one and how do i hook it up? also how about the gear ratio.

i found a guy selling a 1987 sunrunner 220cv with a 4cyl and 19 pitch prop that claims 32mph. my boat will hardly get on plain with a 19

 

[nailem]

Re: help with Q-jet stumble and maybe down on HP (update: 6-20-08)

Re: help with Q-jet stumble and maybe down on HP (update: 6-20-08)

thank you all for your replies. i finally got a compression gauge. it was not the screw in kind but the press in so not the best but it was what i could get.
1= 125
2= 125
3= 130
4= 125
5= 140
6= 145
7= 145
8= 145
so not the tightest motor but not to bad. like i said it was a press in gauge and i could feel a little leak by my hand. here are some pics of the a few of the plugs. from left to right 1, 3, 5 ,7. one looks a little lean maybe? others look slightly rich? the stumble is all but gone. i think this fall i will put a rebuild kit in but for now it ok. thanks again

 

[RJLeuwen]

Re: help with Q-jet stumble and maybe down on HP

Re: help with Q-jet stumble and maybe down on HP

THAT motor needs to turn at 4600 rpm's for top performane if you cannot get 4600 WOT you need to drop your prop picth down.

If you do not you will be doing a vavle job on it in the near future

RJ

 

[RJLeuwen]

Re: help with Q-jet stumble and maybe down on HP

Re: help with Q-jet stumble and maybe down on HP

You may need to adjust the spring tension on the air dam (which is the plate over the top of the secondary butterflies) if it is to loose it will open up tosoon a cause the stumble or bog when mash the throttle down.

RJ

 

[nailem]

Re: help with Q-jet stumble and maybe down on HP

Re: help with Q-jet stumble and maybe down on HP

RJLeuwen, are you referring to the air valve adjustment? if so im getting mixed advice on weather or not to mess with it.

 

[nailem]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

bump

 

[Bondo]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

so not the tightest motor but not to bad.

Ayuh,.... I can agree with that....

The plugs look like they getting Detonated,... Aren't the ground straps rounded right off,..??
The White on the sides says Detonation.....

Running the timing so advanced could possibly have done it, without knowing the running time,+ history.....

I still think you're Carb is just plain Junk,+ causing your Issues.....
But,.....
That's just My Opinion.......

Btw,.....
Checking to be Sure that your TDC timing mark is Correct, as noted by MikDee is Well Worth the Effort......

Oh,... Your gear ratio should have been the 1.5:1,... Which is as High as they went,..
So that's Not the Issue....

 

[nailem]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

in my reply # 24 i did take mikdee's advice and checked the timing marks. they are right on. i also set timing back and is now about 8 1/2* BTDS probably closer to 8*. i think your right bond-o i need to rebuild the carb but i think i'll wait till fall.

i think its just the angle in the pics because there is no rounding off. the #1 plug is the whitest. the rest did not look bad. the plugs have about
10hrs on them at 8* then i advanced it to the 9* and ran 4hrs now i have it back to 8* for the last 4hrs.

i cant find the gear ratio on the drive. i looked on the port side just under the second bolt. i scrapped the paint of and nothing. the only numbers stamped there ar B443554 and a large F

 

[Coors]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

White, on a plug, is a problem. Tan is good.
You need to find the timing/lean issue before waiting until fall.

 

[Bondo]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

White, on a plug, is a problem. Tan is good.
You need to find the timing/lean issue before waiting until fall.

Ayuh,... It'll be Aluminum from the pistons Soon.....

 

[nailem]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

i think i'll put new plugs in and run it ( can always keep these ones for next tune up) and see how they look. the white one #1 might be from the advanced timing i was running and the others look good to me.

 

[MikDee]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

Wait, are those Bosch plugs I have no use for them, I wouldn't put them in my car, much less a boat! Or are they no-name plugs? they have to be crossreferenced from the normally used AC Delco marine MR43 either short, or long, thread, depending on the motor model, & yr., by the looks of the extended tips on those plugs, they maybe too hot of a plug!? This might be your whole problem. Start over by getting the recommended AC plug, so you have the proper equipment to begin with. NAPA should have them.

Or, As Bond-o said, or you might be picking aluminum piston bits off them soon, then it's too late.

 

[Coors]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

If one is white, others aren't= problem.
Check the compression; one cylinder running lean, don't think so.
Manifolds good?

 

[MikDee]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

Usually the front 2 opposing cylinders of the small block V8 (1, & 2) run leaner then the rest, due to intake manifold design, but plugs that are too hot will create, & magnify, this causing a similar effect.

 

[nailem]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

good eye MikDee, they are bosch plugs, not sure of the #'s of hand. i just replace the plugs with the same thing that was in it. when i get the new plugs i will switch.

i ran the boat today for the first time since i drained the 180w gear lube and replaced with amsoil gear lube. top speed was up from 32 to 35 ( these numbers are according to the stock speedo which compared to GPS is 2-3 mph slow, so true speed would be more like 37 or 38) and my RPMs are up from 4400 with 180 lube to 4600 with amsoil. more of a differance than i thought it would make.

so all in all im pretty happy now. im still going to change out plugs and read them after some hours. and make the decision on whether or not to rebuild carb now or at the end of season.

thank you all for all your help and time.

 

[MikDee]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

good eye MikDee, they are bosch plugs, not sure of the #'s of hand. i just replace the plugs with the same thing that was in it. when i get the new plugs i will switch.

i ran the boat today for the first time since i drained the 180w gear lube and replaced with amsoil gear lube. top speed was up from 32 to 35 ( these numbers are according to the stock speedo which compared to GPS is 2-3 mph slow, so true speed would be more like 37 or 38) and my RPMs are up from 4400 with 180 lube to 4600 with amsoil. more of a differance than i thought it would make.

so all in all im pretty happy now. im still going to change out plugs and read them after some hours. and make the decision on whether or not to rebuild carb now or at the end of season.

thank you all for all your help and time.

Wow! A change of gear oil I never would have figured that But, I heard Amsoil was good stuff! Change those plugs to the rec. ones, I think you might be happier still. Good Luck, Mike

P.S. That 17" pitch 3 blade might work for you now, or maybe even a 19" 3 blade. Thats what I ended up with on my 20' SeaRay with the 228hp/305

 

[nailem]

Re: help with Q-jet stumble and maybe down on HP (6-20-08 up date)

im not sure if the amsoil would have made that big of a difference if i would have had the correct gear lube in in the first place. i do know when i was pumping it in it was much easier. i am going to stick with amsoil though. it says it will have the same characteristics with up to 10% water.