DJ my 40hp rude needs more help

caphank

Cadet
Joined
May 10, 2004
Messages
18
DJ my 40hp rude needs more help

Remember me?. I had a 1985 rude 40hp vro(disconnected)electric remote. As suggested, I swapped a good used powerhead and every component that was attached to it to my engine that had a blown #2 cylinder. Took it out for first test run. Engine started easily and idled smoothly. I made all necessary linkages and timing adjustment according to the manual. So far so good. Shifted into gear and started out at 2500rpm. No problem. Taking my time I got out of the harbor(twenty minutes)and then I gradually increase throttle. Got up to 5000 rpm but I wasn't going fast(I'm not worry, engine sound smooth, maybe tach off). Then I pushed(forced)the throttle further and the boat just took off. I saw the tach hit 7000 and I backed it down to 5500rpm. I'm cruising now for a few minute @5500 thinking I fixed the problem and I fishing again until the engine started to "buck", tach needle wavering, engine power surging. Get the picture. Double check all settings and tried different timing settings. No change. But before I came in I remember what you said and when I squeezed the primer bulb the power always return and engine would run smooth for a few minutes. I did this all morning and it never failed. Fuel filter always full. Power restored each timer after pumping bulb.<br />As suggested by several topics here's what I did beforehand. Portable fuel tank w/fresh gas, 50:1 mix, can of Sea-Foam, new fuel line w/ bulb, new fuel hoses in engine compartment,and new spark plugs. I took apart four carbs to inspect and clean, using solvent and a thin wire to clear the passages and needles. Installed the best two. Believe me, there nothing in those carbs now. I took apart one fuel pump for inspection and it look brand new, held vaccuum and manually I can pump fuel out. As I mention above, the coils and power pack and wiring etc. all came with this engine.<br />What scares me is this might be the same problem I had two years ago that might have lead to the damages to my original powerhead. I don't want to go through this again. How can this be? Original problem still there yet every component got inspected, replaced or swapped. I spent days and nights trying to find problems. What did I overlook? Caphank. <br />--------------------------------------------------------------------------------
 

caphank

Cadet
Joined
May 10, 2004
Messages
18
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

Scenerio. Air silencer cover off, motor running. When I rev engine slightly I see fuel vapor coming from holes right above the carb throat. I am guessing because the manual's diagrams are so generic but the picture shows this hole is plugged to cover the jet needle. I don't have an adjustable jet needle, just an orifice screw. But I'm asking myself what if I plug these two hole? Then wouldn't the increase vaccuum at wot pull more fuel through the orifices into the carbs and the result would be more fuel to the engine at wot which would correct the power loss I am experiencing. Just thinking. Could I be right? Caphank. Thanks
 

ob

Admiral
Joined
Aug 16, 2002
Messages
6,992
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

If that engine will hit 7000 rpm ,you are either under pitched on your prop or the prop hub is spun.The fact that you can get the engine to respond in rpms by pumping the primer ball ,suggests a fuel delivery problem.<br /><br />Here are some possibilities:Failing fuel pump,leaky pulse hose from crankcase to fuel pump diaphragm,leaks in hoses from tank to carbs somewhere,carb floats set too low,or restriction in fuel tank pickup tube.<br /><br />What diameter and pitch prop are you currently running and what length and approx weight is the boat?<br /><br />DJ will probably be around tomorrow and offer his advice.Just trying to get you started on a few things.
 

caphank

Cadet
Joined
May 10, 2004
Messages
18
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

Good to talk with someone OB. I have a 12.5x15 prop which came with the motor and been using for years. The motor is pushing an eighteen ft alum Gregor V-hull. I am not a speedster so generally I don't go over 4500-5000 pm anyway.<br />When the rpm hit 7000rpm I sure that was a "spike" in the tach reading, as it only did it that one time( i would be dumb to try to duplicate it). I checked the lower unit and hub. Looks good. <br />I agree it an fuel problem. 99.9% sure cannot be hoses. I replaced every one in engine, even the pulse hose. Tried two different gas tanks and two different fuel lines. Restriction? The fuel shoots out freely into a bottle. Fuel pump? I took one apart. Seal and diaphram like new. Vaccuum and pressure tested(one to one and a half psi as per manual). To me it passed. Should I switch to the other fuel pump just to test/or buy new to be sure? Low float setting? Are you asking me if enough fuel in getting into the bowl? Adjusted according to book. Float drop setting seems useless since the float hits the bottom of the bowl. Carbs? Cleaned. What are the chances all four carbs going bad?
 

ob

Admiral
Joined
Aug 16, 2002
Messages
6,992
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

Thing is ,we don't know what the fuel pump is putting out at 5000 rpm.Obviously not enough or pumping bulb would have little or no effect.I'm feeling that the effect happening by the pumping of the fuel line bulb is the compelling factor.Weak pump or high rpm flow problem.If you ran a separate portable tank with different fuel fittings ,that sort of rules out that issue.Is there a water separator between the fuel tanks tried and the engine?Will the fuel line bulb get completely firm when you pump it up before starting the engine and hold firm?If so,we know that the float valves are holding.
 

rickdb1boat

Supreme Mariner
Joined
Jan 23, 2002
Messages
11,195
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

I may have missed this in the post, but is the original VRO still on there, even though you are not using the oil side of it? If so, I'm with OB on the fuel pump problem at high RPM's. That fuel pump would be almost 20 years old and even though you performed a vacuum test on it, I suspect it is defective. As you can pump the bulb and it runs fine, the carbs are for sure clean and the lines are good. It can only lead to the pump or lack of crankcase vacuum not creating enough pulses to run the pump at high speed...
 
D

DJ

Guest
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

caphank,<br /><br />I agree on the fuel delivery issue. If you are using the old oil injection/fuel pump, I would hold that suspect.
 

caphank

Cadet
Joined
May 10, 2004
Messages
18
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

Thanks for your ideas. To answer your queries, no, there is no water separator. Yes, the bulb gets hard before starting and stays hard. During my test run I can give it a half-squeeze and its hard again. Since both engines are of same age, fuel pumps are too. One was sitting in the garage for two years. I'm going to put that on tonight and try it out. If problem still there then I'll be shopping around.<br />Question for you. Can I put a small electric fuel pump in place of vro pump. Since I'm running pre-mix I don't need vro. This would eliminate the need of crank pressure hose if that was suspect. I let you know what I find monday. caphank
 
D

DJ

Guest
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

Yes, you can install a MARINE electric fuel pump. You will want something that is VERY low pressure. That set up would be a band aid for a more serious problem. However, it may show you where your fuel system is lacking.<br /><br />If you decide to go the electric pump route, make sure it iks M A R I N E rated.
 
Joined
Dec 14, 2003
Messages
20
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

IM NOT QUITE SURE WHAT YOUR PROBLEM YOUR TRYING TO SOLVE?IM GUESSING YOU DONT HAVE ANY TOP END OR ANY HIGH SPEED ACCEALARATION??DOES YOUR MOTOR HAVE A CD-2 IGNITION SYSTEM?? IF ANSWER IS YES,LOOK AT YOUR STATOR UNDER FLYWHEEL FOR CRACKS OR ARKING OR TO MUCH PLAY AROUND CRANK,YOU MIGHT NEED A NEW STATOR OR ARMATURE PLATE UPGRADE KIT,IF I MISSED THE WHOLE POINT OF YOUR QUESTION JUST DISREGARD MY LEFT FIELD IMPUT IM SPUN.
 

caphank

Cadet
Joined
May 10, 2004
Messages
18
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

Hurray!! the problem is solved. I took the boat out Sat. and this time I connected a pressure gauge w/ tee to fuel output. Reading was about 2psi at low demand but would drop to zero during high demand and motor would soon start to surge. Swapped fuel pump. What a different. At idle reading 4.5psi w/ pulsation(vro) and 5psi at @5500-6500rpm. Engine ran smooth all day. Thanks for helping me narrow it down. Questions: What is the max rpm this engine can safely handle and is this rpm setting called the wot? Doing 6500 rpm with ideal condition felt good but I don't want to damage another engine unnecessary. <br />You guys are the best source for info. Caphank
 

rickdb1boat

Supreme Mariner
Joined
Jan 23, 2002
Messages
11,195
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

No more than 6000 RPm's if you want it to last. Go to a higher pitched prop. 2"-3" up in pitch will do it...
 

caphank

Cadet
Joined
May 10, 2004
Messages
18
Re: DJ my 40hp rude needs more help

Re: DJ my 40hp rude needs more help

Thanks again guys for all your advice. You saved me big $$ and tears. Caphank
 
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