2002 25hp fourstroke trouble

[91sseries2]

Hi, im new to this forum and have an issue with a 2002 25hp nissan four-stroke carbed model. The problem Im having is the engine starts fine, idles well but runs erratic under load. It will plane out as long as it stays running while missing in no particular pattern. The engine when it kills will instantly lose fire and mimick what would happen if I were to hit the killswitch. I suspect its ignition seeing how it doesn't have the symptoms of a fuel issue. The fuel lines are new as is the tank. I have checked the ignition components with a multimeter and all checks out well when comparing to the resistance figures given in the manual. The cdi unit is showing very high resistance in the ignition circuits. Has anyone experienced these symptoms? Any help would be very appreciated.

 

[TOHATSU GURU]

Re: 2002 25hp fourstroke trouble

"The cdi unit is showing very high resistance in the ignition circuits."

Does that mean it is not or is within the values?

 

[91sseries2]

Re: 2002 25hp fourstroke trouble

Exactly. My local dealer does not have the plug for this model (25/30) nissan/tohatsu and gave the excuse that this has never been an issue on these motors and they didn't see the need to spend the 3 grand on it. He then gave me the number to call the manufacture and see if I could ship it to them to test. All three ignition coil circuits on the cdi unit read 90 k ohms and should be in the 5-30k range..All logic points to this as the problem. My holdup is if I change the unit I am curious to know what the cause of it was. $400 is some serious coin lol. And thanks for the speedy response.

 

[TOHATSU GURU]

Re: 2002 25hp fourstroke trouble

There is no special test equipment needed for this model engine. All you need is an analog multitester and the service manual. Are you trying to do the tests and do you have a service manual in your possesion or is your dealer telling you what the test results are? And...Whats your zip code?

 

[91sseries2]

Re: 2002 25hp fourstroke trouble

i am using the nissan service manual from internet outboards. And yes it has a chart that states all the resistance values for each circuit. Everything else is within spec. I got the feeling from the dealer that he didn't know the answer to my problem and was just trying to get rid of me. So that information may have well been incorrect. Zip is 70517. I have read many of your post and you seem very familiar with these engines. Do my symptoms match what im thinking could be the problem.

 

[TOHATSU GURU]

Re: 2002 25hp fourstroke trouble

In theory the CD should be the baddie. But, check the pulser coils under the flywheel before you buy the CD. I think the CD has to be in circuit on the engine for the tests to be performed, but, it's been six years since we had a bad CD on a 25/30 and I may be remembering incorrectly. Regardless, you will never know why the CD went bad(unless someone hooked up the battery backwards). Electronics just go pop one day.

 

[91sseries2]

Re: 2002 25hp fourstroke trouble

My dealer said the same thing. He said that cdi changes on japanese motors are very rare. What reason I don't know. Quality?I am very pleased with the performance and reliability of these motors. My only complaint is they are not as popular in south louisiana as other domestics or even honda, suzuki etc. I have checked the pulser coils also and they were within value according to the chart. Would battery voltage affect this? my charging rate while running is 14.5. Is this high? 12.8 with engine off. I followed the rectifier check procedure posted in these forums and it checks out

 

[TOHATSU GURU]

Re: 2002 25hp fourstroke trouble

Your fine on the voltage.

 

[91sseries2]

Re: 2002 25hp fourstroke trouble

well im going to go ahead and get the cdi. Thanks for all the help. Ill post back this weekend hopefully with the results.

 

[TOHATSU GURU]

Re: 2002 25hp fourstroke trouble

The CD module, including shipping, is available from the link below for $120.00 less than that $400.00 price.

http://www.internetoutboards.com/product_list.asp?id=51&pn=2

 

[91sseries2]

Re: 2002 25hp fourstroke trouble

Wow! I had checked the site before even going to the dealer but must have overlooked it. Thanks man thats a big help. I can get back on the water and still have enough to eat this week.

 

[91sseries2]

Re: 2002 25hp fourstroke trouble

Hey I just wanted to comment back after installing the new cd unit. Upon receiving it, I tested it with my multimeter to compare the two. The new one read very similar. Well I installed the new unit on my motor and hit the water. Same thing. I had bought some new plugs but never installed as the ngks I had put in after getting the bought setup where "good". At the dock I decided to install the new plugs for the hell of it. Well what do you know it looks like I found my problem. Hour an a half not one hiccup. I didn't want to post this as my prides a little hurtbut maybe it will help someone else. Then I got to hear my dad gloat about how he was right. Anyway, The plugs looked clean and had a nice tan color to them. Moral of the story, just because you have new plugs don't assume they are good. Thanks to all that helped as I learned a great deal about troubleshooting my motor.

 

[Wee Hooker]

Re: 2002 25hp fourstroke trouble

WoW, Expensive lesson but all's well that ends well. I appreciate your posting the follow up. I'm just getting ready to pull the trigger on a new Mirrocraft 1615 with a 25/30 HP Nissan/Tohatsu. SInce I'm in new territory with 4 strokes in general, It's comforting to know that your problem was minor in the end.

 

[91sseries2]

Re: 2002 25hp fourstroke trouble

Yeah and like I said, when I bought the boat I was having fuel issues because the primer bulb was bad and the carbs were dirty from having sat up so long. I also had a bent propshaft and was in need of a prop. I boat the boat from a long time coworker of my fathers who gave me a great deal. Well when I was fighting those problems I had changed the plugs and went through the carbs multiple times and fixed the lower unit. Well in the mist of all the trouble it never ran correctly. I had just put new plugs in and assumed them to be good as they looked fine and they were new! lol. Well 280 bucks later and a lot of cursing, I have a spare powerpack and great running boat. But the Tohatsu/ nissan seems to be a great reliable motor. I have owned the 3.5 and 15 horse two stroke models and they were always dependable motors. This one was the first I have ever had "trouble" with and that was due to the previous owners neglect and damage. Only issue I have in my area is very few dealers.