1988 40hp M40C Whats normal?

Well, I finally found out why the 40 on my 8'-6" Adventurer SE wasn't making any HP/RPM. No timing! Apparently, I fixed the carb and didn't know that the last guy that had it had the timing severely retarded. We couldent load the motor in the tank, as it just moved the water away from the prop and it RPMed fine, until we got to the lake and the engine just bogged. We finally strapped it securely to the trailer at the ramp, and loaded it at the RPM where it bogged and checked everything. I just advanced the timing a little at a time until the bog went away, whenever my manual gets here I will set it correctly. Since last post, I smoothed the reed/manifold area, installed countersunk hardware there, ported the entry to the reeds, installed Boysen reeds, made a cool aluminum inlet radiused venturi, opened up the exhaust exit in the lower at the rear bearing area, opened up the exhaust slots in the props(I have 4), had the two used props (9" and 11") checked/rebuilt and added cup, replaced the fuel/ oil with new, and am ready to take it to the lake(45 miles) Saturday. Can't wait! I have tried 3 tachs that work on other 2 stroke engines, but none function correctly on this one, (it just jumps around) does the Nisssan need a special tach? It seems to me that this engine should pull a much bigger pitch prop too, what is normal? I have a 13 and 15 also, both new. It didn't seem to like the 13", it took forever to get on plane with just me in the boat before the power mods. I would like to get a working tach before I go to the lake this weekend. Any ideas what I should expect? Anybody know what this rig should do? or even what a jon boat runs like with a Nissan 40 on it? No one around here (Phoenix,Az) has any Nissan experiance on anything! I have heard that this combo in stock condition runs 35/40 MPH, but with a 2 to 1 lower gear ratio and an 11" prop, I can't see that. Thanks for any input. TIMINATOR

Re: 1988 M40C Whats normal?

No special tachometer needed. If you are using an alternator-type tach, make sure you are on the alternator output leads.

Your rig, being that small and light should pretty much fly. After you get the link and sync done, it will be time to try different props. Small timing differences will make a huge difference.

Re: 1988 M40C Whats normal?

It ran 31.9 with the 9" at 6000 rpm, and 32.2 with the 11" at lesser rpm (tach trouble again)with 210 lb driver, big battery, and 8 gallons fuel. Carb is blubbery rich in the midrange and only somewhat rich on top, blackens everything with soot, but runs! Spent some quality time with the carb tonite and learned how to get some more corroded parts apart to clean, some stuff that originally looked pressed together came apart with penetrant and heat. Solvented, carb dipped, ultra soniced, and will reassemble tomorrow. Also removed the yellow top optima (76 lbs) and bought a specified size battery, it weighs only 16 lbs. Once I get it sorted out, I will mill the head, the quench is almost .070!!! That will wake it up for sure, then on to some more tricky stuff. Goal is 50 mph.

Re: 1988 M40C Whats normal?

Carb is back together, sounds waaay different!(in the tank). At same idle speed it seems to have much more exhaust out the prop. Since this is a one carb, two cylinder it can't be a syncronization deal. It is much more responsive and will transition from/to any rpm without hesitation or a bog. What a deal! Can't wait to try it in the lake. It never missed a beat before, even when it was bogging on the transition, but it is smooooooth now! Hope it will pull the bigger props that I have (13" and 15"). I bought them on advise from a prop guru while the other two(9" and 11") were in getting rebuilt. TIMINATOR

Re: 1988 M40C Whats normal?

OK, it doesn't load up. Sounds cleaner, now runs 37 with the 11" prop. Still has lack of low end. Flywheel key is OK. Fuel pressure, good, rechecked reeds(new Boysen-OK), Have talked to several local OB gurus, and no-one came up with any other ideas. I'll keep plugging away..... TIMINATOR

Re: 1988 M40C Whats normal?

While your mods have helped top end, they may have hurt low end. Reminds me of people tinkering with car motors, and after changing to a single-plane manifold, noticing a severe loss of overall streetability. But go back and verify the timing measurements. More advance can be good for hole shot; too much can cause spitting at the reeds -- and boyesen's are known for that.

Re: 1988 M40C Whats normal?

More advance helped the bottom end slightly, barely gets on plane with the 11" prop. Tried with and without carb radiused venturi, air box, different new plugs, and new reeds, have gone back and forth with all parts/combinations. Seen a few of these boats with 25s on em that fly! Tach problem was the tach. wiring all OK. Cleaned/checked/recrimped all wiring. Has good compression, and spark. This motor has never had any power anywhere, but I am finding some top end so far. Offered to have the 2 local dealers look at it, both are very vague, neither has a test prop, and both said that they "know what it is". With neither dealer having a test prop or test tank, I am leery. Neither one has a manual to sell me, and the Nissan one I ordered is on backorder. I would be happy to pay for it to be fixed, but I can't see paying for someone to experiment on it that has no way to test it. The nearest lake is 40+ miles, I am paying more in gas and ramp fees than for parts. In my shop, if I can't diagnose or fix a problem, we don't charge the customer, and remove the new parts. But, I am old school, and I don't work on outboards for a living. Just trying to get the wifes play boat running correctly. TIMINATOR

Re: 1988 M40C Whats normal?

Did you VERIFY link and sync? Small timing changes make a BIG difference in performance.

Re: 1988 M40C Whats normal?

Manual is on backorder. No-one will post any info or P.M. it. Not on several boards that I have posted on. Neither local dealer want to "get involved". One said that: "some of those Jap motors just don't ever work right no matter what you do". The other one said:"the manuals are junk and there are many problems that are not covered that we can't get answers for either". No help. I used to race go-karts back in the day with West Bend, Power Products, and McCulloch, modified most of them and worked on all of them, no problems. Had several medium sized 65-85 Johnson O.B.s on boats, fixed and modified all of them, no issues. Owned Yamaha RD-350s and Kawasaki H-2 750s, modified and street/drag raced all of them, no issues. Got a Chapparal snowmobile motor in my EZ-GO golf cart/buggy, gears, carb, expansion chambers, MSD 6AL car ignition with a homebuilt crank trigger ignition, hauls patootie, no issues. No Seloc manual, No Clymer manual, No factory manual except for a "one size fits all" and that has been on backorder for several months according to my two local dealers. Another Asian motor in my future? I think not. TIMINATOR

Re: 1988 M40C Whats normal?

The manual is not on backorder. I just got one in for a customer last week. You need 003-21035-1 SERVICE MANUAL, 1 & 2 CYL, 2-STROKE $42.47. The manual is not available online because it's copyrighted. Sounds like you have an unhelpful dealer -- or at least one that doesn't understand modified motors. Although most techs are only familiar with completely stock setups, you can always call Tohatsu America directly at 214-420-6440. They are usually very helpful. They may also want to know which dealers are not giving you adequate service. I think you will find that Tohatsu motors are as good as any, better than many, and the best price in the industry.

Re: 1988 M40C Whats normal?

Thanks for that info, its BOTH dealers. This motor was not modified in any way originally when it had these problems. It sat for 6+ years, fuel tank had water, carb full of water because helpful neighbor of guy I purchased it from tried to start it about a year before I got it for my wife. I know enough not to modify anything that doesn't work correctly. When we got it the first thing I did was drain the tank and carb, clean and refill. Attempt to start, didn't, removed/rebuilt carb. Thoroughly cleaned it/ dipped it, reinstalled it, bad fuel pump, replaced it, checked/verified fuel pressure. Checked spark, OK. Replaced plugs w/recomended units, verified spark output. No bottom end. Checked reeds, slightly out of spec/ replaced w/ Boysen- have switched them back and forth with stock ones, no change. Verified compression-128 bottom, 131 top. Removed carb (3rd time) ultrasonic cleaned everything, verified all jet sizes w/parts manual, verified all jet orifices for size- no mods found, none done. Checked flywheel key for signs of partial shearing, none found. Vacuum tested crankcase, no issues, removed exhaust port cover, verified no port restriction/carbon plugging. Connected flowbench to exhaust, verified plenty of flow/HP rating with and without props installed. Factory prop was severely restricted compared to Michigan prop, put it in the mill on a rotary table and opened it up to Michigan flow, modified other new Michigan to even more flow. Tried all props in all combos with timing in test tank and lake. Tried removing cowl, airbox, and replacing with an aluminum flow enhancer, both in test tank and lake in conjunction with prop changes and timing changes. Remixed/changed fuel 4 times and have tried synthetic oil and all "hot-tip" oils. Removed head, checked sealing and for piston/carbon issues, no apparent problems. EVERYTHING WAS REPLACED WITH STOCK COMPONENTS BEFORE AFTERMARKET PARTS WERE TRIED. Factory timing link plastic end was cracked, old owner/helper must have had this problem too. I made a new link with heim on one end and quick disconnect on other end, set to length of old dirt marks on old link, then verified length again with another good running motor. Have 3 new and two modified/hub,repitched/repaired props. Tried 4 different trim angles, new battery, cleaned/recrimped/verified ohms on all wiring, tried bypassing also. Talked to 3 other Addictor owners, all run 11" props for skiing, and 13" or more for joyriding, their speeds run typically 37 w/ski prop, up to 44-45 with speed props everything unmodified. Dealer said Wednesday manual was on backorder. I'll call Tohatsu, then? TIMINATOR

Re: 1988 M40C Whats normal?

You can call Tohatsu, but they do not sell direct so you will not be accomplishing anything. Just do a search on the web and order a factory manual online.

Re: 1988 M40C Whats normal?

True story, except after about a half hour of discussing everything done so far and in what order, and I then told him the next thing that I was going to do is strap the boat down to the trailer at the ramp, and hold it at the problem RPM with my ignition scope on it. The nice man said: by the way, what color is the identification dot on the box? and you have an old ignition scope? I replied "yellow". He said that the yellow one is the oldest and superceded (several times), and most troublesome box. He said that this box can do everything fine except perform under max load at pre-planing RPMs, I believe he said somthing about exciter voltage being too low to allow full output until the RPMs climb. He said it can sound like a carb issue on the transition (it did, because it had that too). Tuesday I will order a new one from an aftermarket supplier he mentioned. I will post his name and the supplier if this works out. P.S to his credit he said that he didn't remember any of the yellow dot boxes surviving much into the 1990s, so he never thought to mention that initially. This may have been the issue that the last owner faced and no-one else could find either. Could also be why everyone and his dog worked on it before I bought it. I'll have the box 2nd day'd in if its in stock, and we'll see. There may be hope yet. I will reserve further judgement till then. TIMINATOR

Re: 1988 M40C Whats normal?

Quite a few dollars, 2 days, great anticipation...... and another $40.00 in gas to get to the lake, $10.00 ramp fee, closed the shop an hour early to get there before sunset, and it runs smoother, but worse. Labors to get on plane as bad as it did a month ago. Spent 2 hrs+ adjusting the timing everywhere, then opening up the plug gap to what the new box asked for(left it at stock gap at first so as to change only one thing at a time) and doing the timing test thing again to no avail. Speed now down to 31-32 mph. Both the electronics mfgrs. rep and Nissan/Tohatsu factory rep were absolutely positive that the box/coil was the trouble. BTW the exciter coil output is within spec. For every 5 guys that tell me what a great motor the Tohatsu/ Nissan is 2 others tell me what I have already found out. P.S. the ex-dealer that told me what crap some of them are is gonna laugh his ass off now. Shoulda bought the 50 Evenrude for $400.00 running with a free test drive(the guy lives near the lake), I've got a hellofalot more in this P.O.S. TIMINATOR

Re: 1988 M40C Whats normal?

What is your WOT RPM?

Re: 1988 M40C Whats normal?

When it was running better last week before the new box, about 6000 w/9" prop, and 5700-5800 w/11" prop, and not too bad out of the hole(but not right). Now about 400-500 RPM off of that. The box maker's rep said NOT to use the 5K ohm resistor plug boots that came with the kit because the 40 needed all of the spark power it can get. He said somthing about the way it is scavenged. So I did what he said and used some new MSD boots I had laying around. Like an idiot, I never thought to bring the resistor boots with me for testing, as everyone said that the box is defenitly my problem. Found an old (looked in a bunch of bookstores for a new one) 2 stroke tuners handbook. Read it last nite and it says that for CD ignitions on a 2 stroke, you NEED the resistor ends to "slow down the spark to make its duration longer", otherwise the spark is too short in time to ignite the air/fuel/oil mixture fully in a 2 stroke. I really didn't think that not using them could be in anyway bad, but after the motor still runs crappy and I read about that, I realized that this motor had non-resistor plug ends on it when I got it. They look to have been non-factory as it seems too. Anybody KNOW about that? I haven't been able to find out the proper exciter/flywheel gap either, but the 2 stroke handbook says set them as close as possible without them contacting each other or the output will be low. My next move is try the resistor ends, and then set the exciter gap closer than the .060+ that it is. I'll go to .040 first and see what happens. TIMINATOR

Re: 1988 M40C Whats normal?

Got manual, few revalations. It says my compression should be 106.6, mine is 124-128, might have been played with before I got it. Might explain why it ran better on premium fuel(91) on the cool rainy day. Putting Tohatsu oil mixed with 100 in it tonite. We'll see... ALSO my timing/carb quadrent puts ALL of the timing in before advancing the throttle at all,(timing is set to book setting), is that normal/modified? If anybody has access to a NS40 C of 1985 or so vintage 2 cylinder, Could you post or e-mail me a pic? Might be why I can't even ease it up on plane either, might be modified. No pic in manual either. TIMINATOR

Re: 1988 M40C Whats normal?

Installed new plastic clips on carb rod,now puts 3 degrees less timing at start of throttle opening. Tried the new NGK OEM plugs, Tohatsu oil, and 100 octane. gained 2 mph, but still bogs getting on plane. Has picked up a slight ignition miss in the last 4 sessions, now has an occasional cough while trying to get on plane. The wiggle test now (it didn't before) shows slight resistance change on the exciter and trigger coil leads, mebbie bad ground or ground wire. Will rewire those next. Exciter voltage now jumps around too, I'll see if the rewiring changes that. When the voltage fluctuates, the engine coughs, but only above about 2000 rpm. If not I guess the exciter has finally deteriorated. It may have been the problem all along, but the voltage was steady and in range, but it is not now. I don't throw parts at problems, I find out what is bad for sure before replacement. This motor has had much more than its share of gremlins. Another talk with the ex-dealer clarified his earlier statement: "that some of these Nissan/Tohatsus can't be fixed", but rather with the multiple gremlins he has experienced with these older ones, the customer wouldn't pay for all of the time to track everything down. He's right, if this wasn't my wifes boat, I couldn't charge enough to make it worthwhile for my time. P.S. the stator plate brass bushing is worn enough that I will either buy another, or machine one up on the lathe. As far as the one opinion of one of the dealers that "the repair manual is a P.O.S.", there are quite a few specs missing/omitted that should be there. Reluctor, alt.stator, and trigger coil gaps, compression ratio, throttle cam specs for timing at throttle pickup, peak torque and its RPM, and recomended prop pitch for boat length/weight, and typical performance charts, among others. The statement from the Tohatsu America tech line rep. that: "no one in this building has been here long enough to know anything about that motor". Was very depressing. If I live long enough to fix this 40C, I will post everything that was wrong/worn out. This whole project reminds me of the old Chrysler "Top Tech" competition that was held every year. They took 50 identical cars and screwed up about 25-30 of the same things to each car for the techs to fix. The winner was the team that found and fixed all of them first and made a lap of the track without incident. They had a stock of all bad replacement parts and a bunch of things that weren't broken too to throw everyone off track on the repairs. The only difference is its my time, money and I'm not gonna win the scholarship if I can do it. TIMINATOR

Re: 1988 M40C Whats normal?

The funniest part of the manual is on the timing specs: 25 degrees BTDC (77 degrees BTDC fahrenheit). TIMINATOR

Re: 1988 M40C Whats normal?

Changing exciter coils (4 of em, cant find a new one) changes some symptoms but not the bog. Two of them eliminate the miss/cough but do nothing for the bog. The other two are worse. Was going to have mine rewound, but was cautioned by several shops that it will be gone from 6 to 10 weeks, regardless of promised return time. Thats B.S. Tohatsu and CDI said to "call when I find out what it is", and let them know. Not much help there. Neither place will return my calls anymore. I am starting to believe the guy that said: "some of those Nissans can't be fixed". I really believed at first he meant :"at a reasonable price". Now I'm not so sure. As far as post #8 stating: "small timing changes make a big difference in performance", timing changes make only a small difference in this motor, (when initially set to stock specs), at any rpm. I have spent another several hundred dollars on this motor since the last post, and I am tired of peeps on several boards telling me and others that all problems are related to the "link and sync". One carb = nothing to sync there, timing = set at idle, and full throttle. The throttle cam sync relates to a pull start only for throttle setting for start and max throttle settings in reverse, and not any of that relevant here. Looking for an Evinrude/Johnson 50 or 55 2 cylinder to purchase. Then the spam sections everywhere will have a listing for this junk motor for parting out. I have never run across this lack of knowlege with a Merc, or Rude. It has cost easily twice what it can be worth in replacement parts alone. I have done everything that anyone has suggested, and more. I am tired of playing. I wonder how long this post will be here..... TIMINATOR

Re: 1988 M40C Whats normal?

" Neither place will return my calls anymore"

I can guess why...

Re: 1988 M40C Whats normal?

No, you can't. I have talked at length with the factory rep, he said he could not give me any more advice, he doesn't know anything about the "old" motors, said that no-one in the building did. Said to call him and let him know what it was when somebody figured it out! I also asked for a sharp dealer reference, they wouldn't do that. CDI electronics and Tohatsu America told me absolutely that the CD ignition box was bad, Tohatsu actually suggested that I call CDI. Without any qualms, I bought one from them(CDI) at the normal price, and had them second day air it here. It didn't solve or change the symptoms, actually it did make it slightly worse. I called back and talked to the same person that told me that it was definatly the box, and asked him,"what should I look at next?" He said that he would check into it and call me back in a couple of days. Never did. I have left messages three times in the ensuing 2 weeks without a call back. I have never been a smart-a**, never been a pest, and bought everything recomended by the dealers, and ignition place with no regards to what price was asked/paid. I have been in business for 35+ years and have been on the recieving end of the phone as someone whom gets his brain picked on a regular basis, and as such I don't like it if a non-customer takes up my time and then purchases their parts elsewhere. I do not and never have done it. I can only assume one of two scenarios at this time: 1: nobody out there in cyberspace has had a similar problem and fixed it. or 2: somebody has fixed a similar problem, but is not close enough to make any money on it from me. Again, I am not being a smart-a**, but I have not gotten enough help to solve the problem, and am quite frustrated. TIMINATOR

Re: 1988 M40C Whats normal?

I get what you are saying, but...Two people at Tohatsu are very experienced with the 40 C. Tohatsu sells the CD through their dealer network so telling you to buy one from CDI is retarded...I'm not calling you a liar, I'm just telling you that whomever you spoke to wasn't on the ball. That engine has been out for 27 years now and virtually any Nissan or Tohatsu dealer that has been a dealer for over 12 years should be able to fix it without much effort. That doesn't mean that you can fix it as you don't have any experience with that brand/model. There is no substitute for actual experience. While you may have 35 + years with whatever field you are in it doesn't really count towards this engine. I've got 47 years in outboards and 27 years with Tohatsu/Nissan. I have zero years with Evinrude and would not kid myself that I am qualified to work on one. I commend your desire to repair this engine, but slamming Nissan/Tohatsu because you can't find the problem yourself is inappropriate.

Re: 1988 M40C Whats normal?

Not to call you a liar, but the reason that I called CDI was because the Tohatsu rep told me they did not have the replacement box available, as did both local dealers. I got the number directly from the rep at Tohatsu America, right after the rep told me the Tohatsu/Nissan dealers couldn't help with the parts. If there is in fact two reps at Tohatsu that know that motor, please tell me whom to ask for. Again, the rep I talked to said that: "no-one in the building knows anything about that old motor".The reason that I will not take this engine to either of the local or Havasu(195 miles away) dealers is that not one of them has a test prop or a tank bigger than mine. In my tank with the application of throttle, the engine bogs for a short time(a second or so), the prop pushes the water away, and unloads it, allowing the rpm to quickly rise above the bog point. I was told by the dealers that they would work on it, but couldn't test it any better than I could. I would have to pay and pick it up, take it to, and test it at, the lake and return it for more work. The Havasu dealer said that if I could hang around there during the week, that I could take it to that local lake as many times as necessary to test it after they worked on it,(ramp fees again, and I have to pay to stay in Havasu)The repeated test thing is what I have been doing now at the local lake. The local lake is about 42 miles away, and the ramp fees are $10.00 for each test. It is not your or my fault that the quality of local(within 200 miles)service is lacking. Again, if you know whom to speak to at Tohatsu, please share the info. There are a whole lot more Evenrude/Johnson dealers, parts, and techs here, thats why that option looks good if nothing else works out. TIMINATOR

Re: 1988 M40C Whats normal?

3A1062402MC.D. IGNITION UNIT 25C2/30A3/40C-WITH INTERNAL COIL$278.47$167.08Notes AVAILABLE

Ask for Keith or Alan. Keep in mind that the official policy is to refer consumers (anyone who is not an authorized N/T dealer) to local dealers for service. IE While they will help a consumer or non dealer with limited technical support they aren't in business to take business away from that local authorized establishment. So, they are usually willing to hep on a specific technical point, but the are not going to do Outboard Repair 101. I feel your pain about dealers, but there are actually less Evinrude dealers than there are Nissan/Tohatsu dealers. The problem that Tohatsu routinely faces is that they do not require much of a monetary commitment to become or maintain status as an authorized dealer so...There is some dead wood out there.

As to the actual problem with the engine...Bogging is a symptom for a large variety of possible problems. The tried and true method method to determine the cause(s) is to test the ignition system first as you can eliminate that with a multitestor. You have to use an analog meter by the way. Next do a quick inspection of the block and run a leakdown test. If all is well, it's time to do a fuel system test starting at the fuel itself and working through to the reeds. The problem is in there somewhere so you or someone else just has to keep repeating the tests until it becomes obvious as to what is wrong. Assuming you have run through everything correctly the cause will revel itself. One bit of advice I can give you is that in a case where diagnosis does not seem to be working its usually because something obvious and minor is the culprit. IE Double and triple check the things that you know CAN'T be wrong.

Re: 1988 M40C Whats normal?

I already have the new CD Ign box from CDI, (a month + ago), it runs worse with it, with or without the resistor spark plug ends(they said to try it both ways). Which is why the several exciters were later tried. Two more exciters since the last post. A total of 6 of them. The new / rewound one is worse than the other ones! Was told by a reliable tech guy that the compression test "won't always show a problem on a two stroke, you NEED to leak it down". Been there, done that before, don't remember if I posted that but redid it, again. 6% on the top cylinder and not quite 7% on the bottom one. He also said at 12% the motor is junk and won't have any bottom end. Still no answers. Still lookin for that 50/55 Evenrude/Johnson. TIMINATOR

Re: 1988 M40C Whats normal?

FIXED IT!!!! I just needed to think like the engine builder/tuner that I am, not the outboard mechanic that I'm not. Cost was under $70.00!!! All of the dealers, factory guys, and aftermarket parts mfgrs, had no clue. I just had to listen to what the MOTOR was telling me, not what every one else was. Now, I make it faster! thats what I get paid for in my shop. I have a laundry list of plans... P.S. if anybody figures out what it was, I will verify it. TIMINATOR

Its been a while, but how did you fix this? The above must have been frustrating, but it gives you an opportunity to work through the whole motor and learn about all possible issues