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View Full Version : 85 carb motor major surge problem help!!


dawsoncharles
06-19-2010, 06:07 PM
I have a 85 classic stars and stripes with 600 hrs. It ran great last summer when we put it away. This year I could barely get it started for the season. Now it will start great idle and rev perfect on the lift. put it under load in the water and anything other than idle it will surge very badly or backfire and die. If I hold the carb butterfly almost shut it will run without the surge. obviously its starving for fuel. Had the carb cleaned checked vacuum all floats are fine jets are clean. Put in new fuel filter plugs cap rotor etc last season but have not replaced this year. can mechanical fuel pump do this or is it either good or bad. somone said fuel tank vent could be stopped up or bad fuel line? any and all help will get my kids back on the water sooner. Thanks so much

keith3613
06-19-2010, 06:50 PM
I had the same problem with my 1984 Stars and Stripes. It was the carburetor. I had the carburetor rebuilt and it runs like it was new.

ecproductions143
06-20-2010, 01:31 PM
I had the same problem with my 1984 Stars and Stripes. It was the carburetor. I had the carburetor rebuilt and it runs like it was new.

pull your bowls off each side see if theres some trashon the needles or something that has it hung SHUT or just simply take a screw driver and tap on the bowls with the handle end to see if you can break it lose. Regardless it prolly needs to be rebuilt $60 for a kit or $500 for a new one.If you decide to rebuild it go to advance guy a gallon of carb cleaner and and soak everything real good overnight then blow it out ( every crevis/hole/port) with compressed air and carb cleaner in a can GL

glassmaster
06-20-2010, 08:16 PM
dawsoncharles I had the same symptoms with my motor and it was my carb. Same hard starting no power under load back fire etc.
You need to rebuild the carb. Call Holley and give them the carb serial# and they will tell you which kit you need. Shop around on the web or get your local auto store to order it you should not have to pay anymore than $25-$27.
Definitely get the gallon can of carb cleaner that ecproductions mentioned makes the job effortless and you can reuse it if need be.
It will definitely be worth it.
Have you rebuilt a Holley before?

dawsoncharles
06-21-2010, 02:24 AM
well thanks so far for the input guys I am lucky to have found this site. No I have never rebuilt any carb before. I took the carb off and took it to a local mechanic that said he didnt think it neede rebuilt? said he took apart and checked the jets for clogs and make sure the floats were free etc. we did replace the small diaphram type deal on the side of the carb but that was it.

dawsoncharles
06-21-2010, 02:28 AM
What in the carb that gets rebuilt will contribute to the fuel delivery problem. could the choke adjustment make any difference? Like i said before if you trick it by hloding the primary butterfly almost closed it seems to run ok although have not tried it at high speed. Thanks again. should or could i attempt the rebuild or should i take it somewhere and will it need tuned after that?

H20skeefreek
06-21-2010, 07:12 AM
I had the same problem and it was my fuel pump.

thatsmrmastercraft
06-21-2010, 09:47 AM
well thanks so far for the input guys I am lucky to have found this site. No I have never rebuilt any carb before. I took the carb off and took it to a local mechanic that said he didnt think it neede rebuilt? said he took apart and checked the jets for clogs and make sure the floats were free etc. we did replace the small diaphram type deal on the side of the carb but that was it.

That was the vacuum diaphragm for the secondary side of the carb.

You could have a vacuum leak. With the engine idling, or running as slow as possible, spray some carb cleaner around the base gasket of the carb. (Caution required here as carb cleaner is very flammable. Having a fire extinguisher on hand is not a bad idea - but I have never had a problem doing this.) If your engine speeds up you have found your leak. Base gaskets tend to dry out end leak eventually. There is a gasket between the manifold and spacer, and another gasket between the spacer and the carb. When replacing, buy the thickest gaskets you can. They seem to seal better.

dawsoncharles
06-21-2010, 11:25 AM
I did do that already and thought I found the problem because on that vacuum secondary side the spray did make the engine speed up. The mechanic that inspected the carb told me there was a openening on that side that can draw the spray in. He said that they are often plugged but cause something maybe choke to heat and fail early? I believe that is what he said. The guy at the auto store also said this port can draw in the starting spray? Not sure if I should start with replacing fuel pump or rebuilding the carb or take carb back down to the lake and try again in hopes something changed since guy took apart to check for any issues like stuck float or clog? Its a two hour drive so getting little frustrating. He seemed to think it may be a filter or possibly fuel tank vent or possibly fuel line

thatsmrmastercraft
06-21-2010, 11:38 AM
I assume you have the ability to run the engine at home either with a 5 gallon pail or on a fake-a-lake. With the engine running, try wadding up an old t-shirt and pushing it onto the top of the carb to cut off all the air supply. If the engine keeps running at all, you have an intake manifold leak. You can also check the edges of the intake with carb spray.

Have you verified that the firing order is correct? A crossed wire could do that. When I got my boat, one of the several things wrong was the firing order was out of sequence.

dawsoncharles
06-21-2010, 11:46 AM
yes firing order is correct.the crazy thing is the boat ran fine when it was put last winter. Spring comes and here I am. Like I said I had a lot of trouble even getting it to run. It would fire on starting spray but wouldnt stay running I ended up pouring gas down the carb numerous times( i know that is dangerous) and then eventually would idle but could not rev it up. After continuous tries and nursing the throttle up I could get it to run at high rpm in idle. I just kept stabbing the throttle until it seemed to work it out. Put it in the water and now have the terrible surge under load. btw the boat will stall quickly if you just close the primary butterfly all the way but if you hold it just very slightly open it seems good

thatsmrmastercraft
06-21-2010, 12:04 PM
I read through the post again. It sure does sound like a fuel volume issue. You might disconnect the fuel line at the carb, clamp a rubber fuel hose over the metal line and do a volume test. I don't remember the specs for volume and time cranking (again exercise caution here). Someone will probably know the specs, or check a manual.

dawsoncharles
06-21-2010, 02:26 PM
well to let everyone know, because of the distance between me and the lake/boat, i ordered a fuel pump as possibility and a rebuild kit per most recommendations. I am planning on going ahead with the rebuild and bolting it on this weekend to see if that fixes it. if not i am installing the fuel pump and moving on from there. Thanks for all your input and will def post my results for hopefully somone elses benefit. Thanks again what a great resource this is.

TMCNo1
06-21-2010, 02:42 PM
If it gets where it won't idle right and you get large amounts of black smoke out of the exhaust, it's the power valve that needs replacing. It has a hole in it and is flooding the engine.

Artus
06-24-2010, 10:26 PM
I have an 88 Prostar 190 with a similar problem. It runs good cold at idle, but bogs down/cuts out once up to a certain speed. Then it doesn't want to start when hot and wants to die at idle. I rebuild the carb and I'm still having the same problem even after adjusting what appeared to be a bad float setting. Other than the carb cleaner spray suggestion, any thoughts? I think I also saw fuel pump mentioned. Thanks for any feedback!

oldairboater
06-24-2010, 11:08 PM
You need to trouble shoot one problem at a time. Check the vent. Check the fuel line. Replace the fuel filter. Check the fuel pump. Check one thing at a time and make sure that everything you check is right---then move to the next possible problem.

Alanb
06-24-2010, 11:40 PM
Fishing for a fix for mine as well, rebuilt the carb (4010) and replaced fuel filters. Runs very rich, it won't run at all if you plug in the crank case vent hose in the intake. Installed new plugs as well. Waiting for a cap and rotor from Ski dim, not sure what to look at next.

thatsmrmastercraft
06-25-2010, 01:21 AM
Fishing for a fix for mine as well, rebuilt the carb (4010) and replaced fuel filters. Runs very rich, it won't run at all if you plug in the crank case vent hose in the intake. Installed new plugs as well. Waiting for a cap and rotor from Ski dim, not sure what to look at next.

That sounds like a blown power valve.

oldairboater
06-25-2010, 10:33 AM
I am new to this web site and to Mastercraft boats. I am not new to boats. Vapor lock issue is a new one for me. I don't have that problem now and probably won't because of my set up. Just reading these post there are a lot of fuel problems on here and usually it is after storage from winter. With the big blocks and Holley's we run in the other boats we will have issues if they sit. We fight alcohol deterioration on fuel lines and it's affinity for moisture. We don't winterize--we use the boats year around but we also use fuel stabilizers. Sitting gas is a problem here due to humidity and fuel separation. I will partially winterize my Mastercraft this year in between use just in case we get to freezing temps but I will use fuel stabilizers all year around anyway. Seems some of this could be prevented. Glad this site is here. I appreciate the practical knowledge.

Alanb
06-25-2010, 06:11 PM
Well, slapped in the new rotor and cap and life is good to go.. Thanks for the help!!