1990 MARK TWAIN MTX223 V SONIC NO POWER

[LARRY200050]

IT HAS A 570 IN IT SOMETIMES IT GOES GOOD MOST OF THE TIME NOT ENOUGH POWER TO COME UP ON PLAIN. REPLACED FUEL LINES, FUEL FILTER, REBUILT CARB, REPLACED PLUGS, WIRES, CAP, COIL, ROTOR, AND ELECTRONIC PARTS IN DISTRIBUTOR. CHECKED FUEL PRESSURE AT 6PSI AND COMPRESSION TEST AT 150LBS PER CYLINDER . I DONT KNOW WHAT TO DO FROM HERE . THANKS FOR ANY HELP .

 

[Maclin]

Welcome aboard!

Some questions so we can help more...

What size and style boat is this? By the description it sounds like 22 foot or so. Bow rider or Cuddy or day cruiser, or walk-around, etc.

Has it always run like this for you?

Do you know what prop set you have on it now?

Describe how you take off, do you go full throttle each time or ease into it sometimes, any difference between the two.

Does the bow rise significantly when taking off hard?

Are you familiar with the power trim, to start with it all the way down, then gradually bump the trim up as it accelerates.

Does the boat have trim tabs, do they work, are you familiar with their purpose and operation.

 

[LARRY200050]

IT IS A 22 FT CUDDY WHEN I BOUGHT IT LAST YEAR ON THE TEST DRIVE IT WENT FINE. IT SAT FOR 2 WEEKS BEFORE I TOOK IT OUT AGAIN THEN IT HAD NO POWER. I HAVE HAD IT ON THE WATER ABOUT 9 TIMES AND MAYBE 3 OF THEM IT RAN FINE. ONCE IT HAD NO POWER THEN SUDDENLY IT PICKED UP AND RAN FINE. I DONT KNOW WHAT THE PROPS ARE OTHER THAN IT IS A DUAL PROP.I HAVE TRIED TO EASE INTO THE THROTTLE AND TRIED TO GO FULL THROTTLE AND MAKES NO DIFFERANCS.WHEN YOU GET INTO THE THROTTLE THE BOW RAISES WAY UP BUT NOT ENOUGH POWER TO COME UP TO PLAIN WHEN TRIMMING UP. IT HAS TRIM TABS ON BUT THE INDICATORS DO NOT WORK SO I KEEP THEM UP ALL THE TIME.

 

[Maclin]

Does it start right up every time? Or are there starting issues, like the carb is flooding or similar?

When did you do all the tuneup and carb rebuild? Just wondering if you did all that because of the way it acts, or as routine maintenance then it started acting up. It seems it is most likely a fuel delivery issue of some kind, too much or not enough. Are you running the stock dual inlet Holley 4barrel carb that it comes with? How much would you say you know about carbs? Who did the rebuild?. Was the fuel bowl float level set correctly with the sight plug out? Fuel should just want to run out when the level is correct when the sight plug is removed. This is for both Primary and Secondary fuel bowls.

When it will not plane out do you hear a lot of throat noise from the carb? Like the secondaries are opening too soon? That carb, if stock, is a dual inlet Holley with vacuum secondaries and has a very light spring in the secondary vacuum pod. I would not recommend this to anyone unless I have experienced their symptoms in person, but I changed the secondary vacuum opening pod spring in mine out to a stronger spring because the secondaries were opening too soon and staying open too long. You can tell if this is happening if when the throttle is at about 3/4 throttle and you go to full throttle nothng much happens bue more noise from the carb. Then when you come back to half throttle or less there is a pronounced whoosh-shoop noise from the carb.as the secondaries try to close but hang open just a bit as there is no direct throttle linkage to the secondaries. That carb when new comes with a warning that the secondaries can actually start opening when the primary is choked.

 

[LARRY200050]

IT STARTS RIGHT UP AND RUNS GREAT HOOKED TO THE WATER MUFFLER. REVS RIGHT UP NO SKIPPING OR ANYTHING. WHEN ITS NOT PLANING OUT IT SOUNDS LIKE THE MOTOR IS LABORING WITH NO POWER. ONCE IT WAS DOING THIS THEN ALL OF A SUDDEN THE MOTOR JUST STARTED TO GET LOUDER AND PICKED UP SPEED THEN PLANE OUT. I DID ALL THE WORK TO TRY GETTING IT TO RUN RIGHT. NOT TO GOOD ON CARBS BUT I REBUILT IT ON MY OWN ,PUT NEW MAIN SEATS AND NEEDLES AND CLEANED UP THE MAIN JETS.THE FLOATS ARE SET SO PRIMARY IS JUST AT BOTTOM OF SIGHT PLUG AND SECONDARY FUEL IS JUST RUNNING OUT OF SIGHT PLUG. I WAS TOLD THIS IS A FAIRLY NEW HOLLY 4 BARREL THE PREVIOUS OWNER INSTALLED.FROM ABOUT 1/2 THROTTLE UP DOESNT SEEM TO MAKE ANY DIFFERANCE.

 

[LARRY200050]

I GOT THE NUMBERS OFF THE CARB THEY ARE 80670-3 DATE CODE 1871 IF THIS HELPS TO TROUBLE SHOOT MY PROBLEM.

 

[Maclin]

​Since a couple of times you mentioned it woke up and ran great, so I am sticking with the fuel delivery angle. When was the last time the water separating filter was replaced? Did you dump the contents to see what the filter has trapped? When you do this a new filter needs to be put in, do not re-use. If the filter contents show problems like water, crud, discoloration of fuel then the carb may have blockage problems again.

You could have a propping problem, would be nice to know what propset you have on there now. On the aluminum props, usually painted black, the numbers are usually between some blades horizontally. Aluminum sets are B series, like B7, B6, etc. Lower numbers indicate lower pitch but there is no direct correlation from Volvo as to the pitch in inches. Stainless steel props are C series, C7,C6, etc. The numbers relate to the same pitch as the B series.

That list# points to a later model Holley Avenger series carb. Does it have shiny polished aluminum looking exterior like the pic I (hopefully) attached? OEM carb would have been the duller finish but painted over with Red, as in the 2nd pic. Also look at the vent tubes, they should be a J shape exiting from between the metering plate and the bore aiming into the bore itself. If the vent tubes are just angled then that is not a Marine carb. The shiny carb shown in the attached pic is an 80670 from the Holley site and is not a Marine carb, so if yours is identical then someone has replaced the original with an automotive carb, so tuning and Marine specific items, like J-tube vents, will be missing. Yours may be a Marine version that is just not in the catalog, can you post a pic of what you have?

If it is indeed a stock 670cfm Avenger 4150 style then it is probably too lean for the 570 application. The CFM is adequate, but tuning items like the power valve will be too high of a number, and the jets are more than likely too small. Also the vacuum secondary spring will probably be too strong, the lighter the spring the sooner and more radical the secondary opening event.

Non-Marine 670cfm Avenger...:






OEM carb for the 570, "older" 4150 style, painted Red, shows J-tubes...:

 

[Maclin]

To Frantically Relaxing... Hey FR, recognize that red carb pic?

 

[LARRY200050]

THE CARB PICS DIDNT SHOW UP BUTI LOOKED AT MY CARB AND IT IS NOT A MARINE CARB.THE PROPS ARE ALUMINUM WITH B6 ON THEM.DOES THIS MEAN I NEED TO GET A NEW CARB?

 

[LARRY200050]

FROM WHAT I HAVE READ I NEED A MARINE CARB. WHAT MAKE AND MODEL WOULD YOU RECOMEND FOR MY BOAT.

 

[Maclin]

B6 sounds about right. I run B5's on mine still, kind of leftover from the smaller lakes in Kansas, we mostly did water sports not much long range cruising. I am going to a B6 set "down here" in north Texas since the lakes are bigger and I have a smaller boat for the watersports now.

If you click on my name, and get to my profile and open the Media tab, you can see a vid of mine (22 foot Cuddy with the 570/DP) taking off with the B5's. Actually I do not go to full throttle right from the get-go. There is no reason yours should not perform like that, so hang with it for a while to get it sorted.

 

[Maclin]

Yes, you need a Marine carb. There are enough subtle differences plus a couple of major items related to safety that make it a must to have the Marine version of any carb.

You can try yours just for testing to help determine if it is a carb problem or not, just realize this is a short term trial period so to speak.

If the carb you have looks like the shiny one in those pics, then I would try a stiffer secondary spring first. This will help troubleshoot your issue. What we are trying to do is eliminate any secondary opening bog and run as much on the primaries for as long as possible to see if you get more uniform acceleration. You will need a spring kit from Holley if you decide to try out different spring rates.

Here is a link to the spring kit, these are available at a lot of automotive parts houses that have Holley performance parts...:
http://www.holley.com/20-13.asp
There is a video on that page that is very good, describing the secondary opening system and how to tune it. I would watch that first before trying any of my suggestions.

Your carb will or should have the quick change top on the secondary vacuum pod, that black unit just to the left/aft of the choke in the pic, also shown and described in the video. If yours does not have this config then you can still change the spring but it is not as easy, as you will find out from watching the video, and in all practicality requires you to remove the carb. If you have that quick change kit then this can be done in the boat. With the quick-change there is a cap across the top that can be removed with two screws, it has a sealing rubber gasket. The spring will come out that way. Compare the color of it to the springs shown in the link, I have also pasted in the chart below right from the PDF also available in that link so you can look it up. If it is plain, well that is pretty strong and you may not get much satisfaction, but still worth trying the black one. If it is one of the weaker springs shown then put the plain one in it and try it out.

Just keep in mind that going too stiff could limit RPM, even though it may accelerate quicker at first and more smoothly.

 

[LARRY200050]

ORDERED A REUILT 600 CFM CARB. WILL KEEP YOU POSTED WHEN I GET IT ON AND RUN IT. THANKS

 

[LARRY200050]

PUT NEW CARB AND FUEL LINES ON THIS WEEKEND AND BOAT STILL RUNS THE SAME. IS IT POSS. THAT THE FUEL PUMP ISNT ANY GOOD. I LOOKED IN THE CARB AT FULL THROTTLE AND THE 4 BARREL ISNT HARDLEY GETTING ANY FUEL. IF I PUT MY TABS DOWN I CAN GET IT UP ON PLANE BUT TAKES A LONG TIME TO COME UP.