Evinrude Outboard Not Getting Enough RPM?

Hey there guys this is my first post. <br /><br />I have recently purchased a 1971 Evinrude 40hp electric start engine w/ electric choke. It is sitting on the back of a 14 foot fiberglass runabout. It has a new impellor, is cooling itself properly, starts and idles perfectly, seems to run smoothly when I rev it up. <br /><br />The problem is it should be going alot faster! I cannot even get that little boat to plain. I have had 9.9 hp is the past and this new engine just doesn't seem to get enough RPM to go fast. When I put the throttle all the way down it sounds like it is only at 1/4 or 1/2 power. (doesnt have that high scream that i was used to with my 9.9hp - the 40hp sounds alot lower) I checked the throttle cable and it is tight and when the throttle is all the way down it is pulling the engine throttle to where it should be for full power. <br /><br />I pulled the plugs and both were pretty well new just with some oil on them, one wasnt more oily then the other.<br /><br />Could it be the prop that is not letting me go faster? (the previous owner says it wasnt the original prop) Could it be a fuel or carb problem?<br /><br />I am very good with cars but am still getting used to this boat thing. Any help would be greatly appreciated with this long weekend coming up in a few days.<br /><br />Thanks in Advance!

Re: Evinrude Outboard Not Getting Enough RPM?

I'm assuming this unit has a single carburetor?<br /><br />First off, do a compression test. Both cylinders should be over 100 psi and within 5-10 psi of each other.<br /><br />Second, are you getting spark on both plugs?<br /><br />Yes, a high pitch prop can cause your situation.

Re: Evinrude Outboard Not Getting Enough RPM?

Sounds to me like one cylinder is not firing. That would present symptoms like you are encountering.<br /><br />Run a compression check, and check for spark on both cylinders. If one cylinder has significantly lower compression than the other, or if one cylinder isn't getting any spark, that would explain the problem.<br /><br />You can also run the engine on the water, in gear, with the hood off, and use a WELL-INSULATED pair of pliers to pull one spark plug wire at a time. If there's a cylinder not firing, no change will happen when you pull that wire. <br /><br />If you do all those tests with no definitive answer, then carburetor or fuel supply issues can be examined.<br /><br />This 40hp motor should plane your 14-footer right out. I have a 14'7' Glastron tri-hull and it planes almost instantly with a 1958 35 hp Johnson.

Re: Evinrude Outboard Not Getting Enough RPM?

OK I will do that compression test and spark plug removal test tonight and post back tomorrow morning with the results. I will also try changing the spark plugs to make sure that one is not faulty.<br /><br />And Yes this unit is a single carb unit.<br /><br />Thanks alot to DJ and CATransplant and I will post back tomorrow.<br /><br />Cheers,<br /><br />Ryan

Re: Evinrude Outboard Not Getting Enough RPM?

Compression was 120 PSI on both cylinders. It ended up being a corroded spark plug wire so it was running on one cylinder. I sanded it down and now it fires up first key turn and idles prefectly, also revs up much higher now. Going to put it into the water tonight and see if it plains now.<br /><br />Thanks again for the help.<br /><br />Cheers,<br /><br />Ryan

Re: Evinrude Outboard Not Getting Enough RPM?

Excellent. Isn't it great when a problem is simple and inexpensive to fix? Would that it were always so.<br /><br />I'll bet it pushes that little 14-footer to around 30 mph. Let us know.

Re: Evinrude Outboard Not Getting Enough RPM?

Hey Again,<br /><br />Wasn't as easy as I had hoped. It definatly runs more smoothly now and seemed to rev up higher when I was testing it in the garbage can of water but when I put it in the water last night it did not plain again. It still has lots of tourque when I put it in gear but still does not seem to be able to rev up high enough to plain the boat. It should be going ALOT faster with my little boat and 40hp engine.<br /><br />I also checked the specs on the prop, it is the OEM spec so that rules that out. Maybe the hub is done on the prop?<br /><br />I am running out of ideas now and really need some help. Do you guys have more things I should be checking out? Could it still be a carb problem?<br /><br />Any help would be greatly appreciated...<br /><br />-Ryan

Re: Evinrude Outboard Not Getting Enough RPM?

Hmm...without a tachometer, it's impossible to tell what the engine RPMs are at wide open throttle (WOT). That makes it harder to tell what's going on.<br /><br />There's no question that this motor should plane a 14' fiberglas boat. None at all. So...it sounds to me like the engine isn't reaching it's full RPM and power. Why?<br /><br />Well, start by checking if the throttle butterfly is horizontal when the throttle control is fully open. You can do this with the engine off, but in gear, to allow the throttle control full motion.<br /><br />If it is horizontal, then you'll have to look elsewhere.<br /><br />Since you say the engine RPM's don't seem high enough, you can probably rule out a spun hub on your prop. You also say that the prop is the original. How do you know that? Pull the prop and look for markings to indicate the diameter and pitch. It's possible that someone put a high pitch prop on this engine for some special use, like pushing a pontoon boat. There are lots of different pitch props that will fit, but not all will work for you.<br /><br />It does sound like you're bogging down and the engine can't reach the proper RPM. Could also be the boat. If the boat is waterlogged, it could be heavy enough to prevent planing. Does it have a wooden deck? Could be water down there...it's a common problem with older boats.<br /><br />Does the boat sit really low in the back when you're not moving? If so, and you don't have water in the hull, try shifting some weight forward.<br /><br />Other things you might check:<br /><br />1. High speed mixture setting, if adjustable on your motor.<br /><br />2. Partially clogged main jet in carb.<br /><br />3. Insufficient fuel delivery due to bad fuel pump, blockage in fuel lines, or an air leak somewhere in the fuel system. Check all the hoses and clamps.<br /><br />4. Bad boat. If the boat has developed a hook or other hull deformation, that could be the problem.<br /><br />5. Wrong length motor. Having the prop too low can cause bogging, as in running a long shaft motor on a 15" transom. The horizontal plate just above the prop should be roughly even with the bottom of the boat.<br /><br />Let us know what you find.

Re: Evinrude Outboard Not Getting Enough RPM?

One other thing to check: <br /><br />What is the tilt angle on the motor? There are three or four positions you can select, by shifing a rod on the transom mount.<br /><br />While this is not absolute, what I like to start with is the tilt position that has the motor's shaft sitting vertically when the boat is in the water. That may not be the optimum position for your boat, but it's a good starting point.<br /><br />If the motor is tilted incorrectly, it can force the bow of the boat up and cause bogging. Just check it and see.

Re: Evinrude Outboard Not Getting Enough RPM?

Well, start by checking if the throttle butterfly is horizontal when the throttle control is fully open. You can do this with the engine off, but in gear, to allow the throttle control full motion.<br />

Click to expand...

Thats the first thing that came to my mind.

Re: Evinrude Outboard Not Getting Enough RPM?

OK, I am going out on the water again tonight so I will try a few of these suggestions and let you know tomorrow if I found anything out. I got the marina to check the prop and they said it was the exact specs for that year and make of engine. It's a 10 1/2 X 12 prop...they told me its probably the hub but it doesnt seem right to me.<br /><br />The boat is very light and is not water logged, was always kept inside a garage for storage.<br /><br />I have already tried paying around with the high speed mixture setting but can get it to go any faster.<br /><br />I definatly want to play around with the tilt but it cant all be that i dont think<br /><br />Its also not a long shaft engine.<br /><br />I will post first thing tomorrow with my finding for the rest of the ideas...<br /><br />Thanks so much again guys!

Re: Evinrude Outboard Not Getting Enough RPM?

Yeah, let us know how it goes, and do change the tilt. It can be that.

Re: Evinrude Outboard Not Getting Enough RPM?

Another thing I forgot to mention: I went home at lunch today and tested it out in a garbage can full of water...it revs up much much higher than it does in the water (to where i figure it should be reving)?? Is this because it blows most of the water out of the can so there is less strain on the prop?<br /><br />So if this is true then that would rule out any fuel pump problems right? because it can rev if there is less strain on the engine...but in the water when its pushing something it wont rev up.<br /><br />Hope this might help you guys in some more ideas...

Re: Evinrude Outboard Not Getting Enough RPM?

Running the motor in the trash can just doesn't cut it. The only way to really test it is on the boat in the water. Sorry. I can blow the water out of a garbage can in a couple of seconds with my 35hp. It runs OK on the lake, too, but the garbage can test just doesn't tell you much. Besides, you'll be running it without proper cooling in that situation.<br /><br />Go to the lake and try it out again, and mess with the tilt angle. If your transom is straight up and down, start with the motor at the lowest possible tilt angle. The goal is to start with the motor vertical and perpendicular to the water surface.<br /><br />If the transom is angled, work from there. If the motor's tilted too far out, it will work too hard, making it bog and keeping the bow high. One position difference from optimum can have a dramatic effect.<br /><br />Basically, it sounds like your engine is running OK and on two cylinders now. If the tilt angle doesn't fix it, then experiment with the high speed mixture setting, making small adjustments at WOT. Too lean or too rich can both cause poor performance.<br /><br />The idea is to adjust the setting toward lean, in small increments, waiting for the setting to take effect, then making the next change. When it gets too lean, the engine will start to run rough. You'll want to back it off toward the rich end to get rid of that.<br /><br />If the setting is way too rich, it may take a bit of time to adjust it, so be patient, and don't make big changes.<br /><br />I'll bet, though, that you're going to find that the tilt angle is going to be the solution. <br /><br />From what you wrote, it doesn't sound like a spun hub, since the engine doesn't make the RPM it should. The 12-pitch prop should be just fine for your small boat.<br /><br />Again, let us know.

Re: Evinrude Outboard Not Getting Enough RPM?

Before you go you might take a permanent marker and mark your hub and prop. after you have run for a bit at WFO stop and check to make sure that the marks are still aligned.

Re: Evinrude Outboard Not Getting Enough RPM?

Hello Again,<br /><br />Took it out last night and caught a 43 inch, 20 pound muskie in the Ottawa River! But it did not change things with the engine. I tried the tilt at every angle and it did not make much of a difference at all...The same thing happens.<br /><br />When I first put it in gear it seems to push very strong and you are moving at a good clip for low throttle position and as you increase the throttle to full it gains only a little bit of speed. I tried adjusting the high speed mixture at WOT and found the best place for it but it did not make much difference in the speed...there is something else that I am missing here. I would guess the boat is only going about 8 - 10 mph. It should be going 3 times that I would think.<br /><br />So what would be the next thing to do? Fuel problem? Fuel Filter perhaps? I really dont want to have to bring it to the marina because im sure its expensive to have somebody else fix it.<br /><br />Any more ideas would be awsome.<br /><br />Thanks again.<br /><br />Ryan

Re: Evinrude Outboard Not Getting Enough RPM?

Good news about the muskie! Not so good about the outboard.<br /><br />If that's all you can get out of the motor on that boat, then there's definitely something wrong. The prop should be OK. I'm running a 10x13 on my 35hp and it's fine.<br /><br />For some reason, your engine is not developing the power. You have good compression but the engine is not developing the proper RPMs, so it's just not making enough power to plane your little boat. You say the boat is light and not waterlogged.<br /><br />In fact, it sounds like it's running at about half power, and that may well be the clue you need. I think it may be dropping a cylinder.<br /><br />Earlier, you mentioned a corroded spark plug wire that you cleaned. I suggest that you get some wire-core spark plug wire and replace both spark plug wires with new ones. In fact, replace the spark plug boots as well. You may have to visit your local OMC dealer to get the right parts, but you should be able to find both at a good auto parts store. Just make sure they're WIRE wires, not the usual suppressor wires. Most auto parts stores sell the wire ones, and standard auto boots will also work.<br /><br />Next, no matter how new your plugs are, put new ones in. They're cheap and you can keep the old ones as a spare set if that's not the problem.<br /><br />This fixup won't cost you much, and might solve the problem. If it doesn't, you still have new wires.<br /><br />I know it's frustrating, but take it one step at a time, starting with the easy, cheap steps like the one above.<br /><br />Next, you might also re-examine the entire fuel system, from the tank to the fuel pump to the hoses going to the carburetor and the crankcase. If the motor is starved of fuel, that could do it, too. Look for air leaks and obstructions. Does your primer bulb pump up hard? Does squeezing the bulb help at WOT when it bogs? If things look old and worn on that inspection, just replace 'em.<br /><br />If both of those fail to solve the problem, then I'd pull the carb, disassemble it, soak the metal stuff in a tank of carburetor cleaner, blow all the passages out, and install a carburetor kit. It's not a hard job, as long as you have the manual, and could solve the problem, too.<br /><br />At some point, your 40 is going to run right and blow you away on your little boat.

Re: Evinrude Outboard Not Getting Enough RPM?

Belay that business about changing the spark plug wires. I just looked at the blow-up of your engine's ignition system. It's the same as my old '58 RDS-20. To replace the plug wires requires pulling the flywheel. Save that for later, for sure.<br /><br />But, speaking of that, your problem still could be in the ignition system. A cracked coil, too small a point gap or other magneto system problems could still be the source of the fault here.<br /><br />Not a pleasant proposition, I'm afraid, since all require a flywheel pulling. It's not a horrible job, but requires some tools, like a harmonic balancer puller and a flywheel holder. I've done it to mine.<br /><br />Looking at a diagram, I can't tell whether there is an inspection port on your flywheel. There is on mine, but I know they eliminated it in later models. You can't see it without pulling the recoil starter. If your flywheel has that port, you can inspect and adjust the points through it. If not, then the flywheel must be pulled even to adjust the points.<br /><br />A too-close point gap setting can cause high speed missing, and affects the ignition timing on the engine. Same thing with worn or corroded ignition points. There are two sets of points on your engine...one for each magneto coil. Two condensers, and two coils. Any of these components can cause high speed problems, including missing and even a dropped cylinder which isn't firing at high engine RPM's.<br /><br />The parts aren't horribly expensive, and the job isn't horribly difficult. But...if you're uncomfortable with this kind of work, it might just be worthwhile to find a qualified technician to do it. It can be tough to get an OMC shop to work on these older outboards, but they can sometimes be persuaded.<br /><br />Or, you can do as I did and bite the bullet and do it yourself. If you have decent skills from working on automobiles, etc., a good manual, and a little time, it's well within an amateur's capabilities.<br /><br />But, if you question your skills, find someone to just do a tune-up on your motor. That will involve them pulling the flywheel and inspecting the magneto components and replacing what needs replacing, plus a carb overhaul.<br /><br />I don't know what the costs are in Canada, but it might be worth an inquiry.

Re: Evinrude Outboard Not Getting Enough RPM?

Have you checked the points on that motor? I have a 1967 40hp evinrude on a 16ft fiberform (heavy fiberglass runbabout). It would idle perfectly on one cylinder. It would act the way you are describing about every 2 years. The problem was always corroded points, causing the gap to change or even close. On my 40 hp I use a 9x11 prop and it pushes the boat at about 12 knots on one cylinder. 22-25 knots on two...;-) <br /><br />Rick

Re: Evinrude Outboard Not Getting Enough RPM?

You've got compression, so it's spark or fuel you're lacking. I'm betting on fuel (clogged main jet). The motor's 35 years old so take CATransplant's advice and do (or have someone else do) a tuneup of the ignition and the carb. Look up "decarb" in the FAQ section too; it's overdue. That motor will be good for another 35 years with proper care. Get it running right and you will fall in love with it.