Tohatsu 25 2 Stroke misfires and lacks power

[12ftLivingston]

Hi Everyone,
Purchased my 12 foot Livingston and it came with a 2004 25hp Tohatsu. From the beginning it would miss and stumble as if it had bad gas. Turns out it did, the tank was cracked in a couple of places! Replaced tank, fittings, fuel lines, primer bulb, removed and cleaned carburetor, replaced fuel pump. I've been lurking on here and have followed the bump to 30hp and have performed that.

My motor still has the issue of intermittently not wanting to get on plane when the boat is fully loaded with gear and people. With just me, it has no problems. I purchased the Seloc manual for the motor which is good, but not great.

I tested my coil and it failed the tests. My local Dealer is the worst for customer service, so I'm hoping I can send some business to another member. Anyone have any other input? I'm fairly mechanically inclined but I don't do it for a living.

Thanks!

 

[pvanv]

Re: Tohatsu 25 2 Stroke misfires and lacks power

The seloc manual is marginal at best, as it covers too broad a product range, and tends to be very "general". That aside, if your ignition coil reads significantly off, a new one may help... but they usually fail to either dead short or fully open. Sometines that can be thermally-related, where it will work OK when cool, but short when hot. If you do diagnose a bad coil, the M25C3 #50039~ uses 3A0060481M, IGNITION COIL W/RESISTANCE CAP, $61.02

 

[TOHATSU GURU]

Re: Tohatsu 25 2 Stroke misfires and lacks power

The tests on the ignition system tell the tale, but your manual isn't known for giving the right values or test procedures. Frankly I would not believe your eyes until you get the factory manual and do the tests as described within.

 

[12ftLivingston]

Re: Tohatsu 25 2 Stroke misfires and lacks power

Yeah, I've discovered that very thing... Seloc is good, but way too generalized and very few realistic diagrams/pictures. Regarding the tests, I found .40 resistance on the primary side and dead shorted on the secondary side. Still starts and runs, just got no acceleration. I may be wasting $ but it seems to be the next step in diagnostic tree. Just glad it's not too old of an engine! Just out of curiosity how much are the actual manuals? And, here are a couple of pics that have me slightly worried... it almost looks like the head gasket is leaking I haven't dove into that yet!

 

[pvanv]

Re: Tohatsu 25 2 Stroke misfires and lacks power

As Luis has noted a few times, it never hurts to do a compression test, and to re-torque all the head bolts. Amazing how things can soften up in a few years of heat/cool cycles. It doesn't look like your head gasket has a blowout, but that doesn't preclude a minor cooling system-cylinder leak.

The Factory service manual is available from any dealer (including me): Part# 003-21035-1, $45.00. It covers the 1- and 2-cylinder 2-stroke Tohatsu/Nissan motors.

The hi-voltage (secondary) side of the coil should be nearly infinite ohms to ground, not nearly shorted, so you may be on to something.

 

[Sea Rider]

Re: Tohatsu 25 2 Stroke misfires and lacks power

When you have checked all fuel, mechanical and electrical related parts and all of them are ok, simply remove head from base and change head gasket, needless to say, both crankcase and head mating surfaces must be inmaculate clean before closing head. Yours is an 8 year oldie, my personal horse which is a 2006 oldie started to have those strange sympthoms, after extensive fuel related and electrical troubleshooting including electrical parts swaps with no aval, a head gasket change solved the problem forever, now runing as a champ, nothing to envy a new ouf of the box horse.

Take advantage to clean all water paths, check thermostat & internal anode condition, clean bolts and crankcase interior threads, "slightly" grease bolts before torquing, if excesive amount is placed in the short run engine vibration will begin to loosen bolts. Torque to max 30 NM evenly in (3) 10 NM increments. Would recommend once head gasket is changed and well torqued, with a thin brush paint with black enamel the head, gasket & crankcase round contour, ley dry, repeat, apply 3 times. Re torque gasket after first 15 hours use. Will need to buy : 346010050M Head Gasket ; 346013030M Basement Gasket.

What Paul states about how amazing things can soften up in a few years of heat/cool cycles, will add hardened gaskets, salt water use and engine not flushed well after use, is true. Misbehaviours usually starts with small sympthoms that worsen with time, higher rpm and use. Nobody ever changes head gasket as a preventive maintenance issue, this is usually the last important part to look after in terms of periodic re torque or gasket change to maintain perfect combustion and engine punch. Note: re torquing a used, dried out /hardened head gasket won't better a thing, you need a new head gasket change for perfect seal against well cleaned & torqued mating surfaces as when engine was brand new.

Happy Boating

 

[12ftLivingston]

Re: Tohatsu 25 2 Stroke misfires and lacks power

Thanks Sea Rider for responding! I think that will have to be a winter type of project when I'm not gonna use the boat for a while... But, while we're on the subject, I remember reading on here about a guy that had sucked part of his impeller up into the cylinders. He said that he had to use a "torch" to free up the bolts.... I don't understand the concept of using a torch to heat up bolts... wouldn't that make the bolts expand and therefore causing them to seize further into the head? Maybe my little brain doesn't understand it, but that makes no sense whatsoever! I have gone ahead and ordered a new coil and anticipate it within a week or so, hoping that that will give the engine back the life that it's capable of! By the way, just as a side note, my engine came from the factory with the restrictor gasket and the timing set at 25 degrees. Made the upgrade to a thirty horse a piece of cake! Thanks to all the people that post and respond on here, you guys are a life-saver! A special thanks to Paul and Elvin, the advice and input you give is priceless! And to you Sea Rider, keep up the great work, I know it takes time and energy to respond, but know that the little people that are out here truly appreciate it!

 

[TOHATSU GURU]

Re: Tohatsu 25 2 Stroke misfires and lacks power

The idea is to heat up the aluminum surrounding the bolt, not the bolt itself. Be careful of metallic dispersion in an energetic manner as the aluminum will pop if you get it too hot.

 

[Sea Rider]

Re: Tohatsu 25 2 Stroke misfires and lacks power

If new coil doesn't fix the problem, re torque head to 30 NM with torque wrench, if betters but doesn't solve issue, a head gasket is mandatory, will take about 1 full day of service. Personally would preffer to lose one boating day, repair and run as a champ than using an engine with tech issues specially during summer. If gasket is letting small water particles pass to combustion chambers, now that you have a modified 30 HP engine, will worsen at 3/4 to wot.

Happy Boating

 

[TOHATSU GURU]

Re: Tohatsu 25 2 Stroke misfires and lacks power

It's not unusual to see seepage on older model engines at the head gasket and it is not a cause for alarm. As long as you have even compression you don't need to worry about it.

 

[Sea Rider]

Re: Tohatsu 25 2 Stroke misfires and lacks power

Being this thread all about "Tohatsu 25 2 Stroke misfires and lacks power", you are already experimenting big problems probably related to ignition coil or head gasket issues.

The only issue using an engine with a defective head gasket is that engine will not run smooth at all throttle range as small water droplets will do their mean part causing misfiring inside combustion chambers, once gasket condition worsens, the worst specially at higher revs. It's up to boater if wanting to fix it or boat with issues untill you never know when you'll be left caput & adrift to Tonga...

Happy Boating

 

[TOHATSU GURU]

Re: Tohatsu 25 2 Stroke misfires and lacks power

There is zero indication of an issue with the head gasket.

 

[Sea Rider]

Re: Tohatsu 25 2 Stroke misfires and lacks power

Ignition coil or head gasket, to be or not to be ? That's the question. It's evident that boater doesn't know anything about head gasket related issues, that's why his post assumes Ignition problems, which could not be so.

Happy Boating

 

[12ftLivingston]

Re: Tohatsu 25 2 Stroke misfires and lacks power

Thank you all for your input... I truly value it, and take your words to heart. For me, the Seloc Manual has pointed me in the direction of the coil... The tests that I performed of Primary and Secondary windings indicate a failure of the coil. To remove and replace the coil will take a very short period of time and allow me to be back on the water quickly. Since I can't seem to find a test for Headgasket, (unlike a car where you can check for the presence of exhaust gases in the radiator) and since I can see what looks to be a potential issue, and since everyone is very helpful and polite on this forum I thought I would throw that out there.... Disassembling the motor and cleaning/scraping and then replacing gasket is not a quick repair. Where a shop would be able to have this completed in a day, it will take me at least three, not to mention hundreds of digital pictures to remember how everything goes back together, some scraped knuckles and probably some broken bolts/stripped screws.
So, I will replace the coil and see how it goes.... I've been wrong before, will probably be wrong again, but I gotta try.
Thanks again!

 

[Sea Rider]

Re: Tohatsu 25 2 Stroke misfires and lacks power

Well, if you are not mechanically inclined for deep interior repairs, work will have to be done by a shop, just for the record, post if changing the coil fixed the problem. Good luck...

Happy Boating

 

[12ftLivingston]

Re: Tohatsu 25 2 Stroke misfires and lacks power

Received the new coil and installed it without any issues, had a big vacation trip planned so I waited to test drive until then. Boat runs great! The new coil really helped. I appreciate all of your input and I'll be purchasing a shop manual over the winter to do some real maintenance, (impeller replace is number one priority). Thanks again! Closing this post. Problem solved.