Spark Plugs for 40hp Evinrude

[rogerrabbitis]

I have a 1969 40HP Evinrude Model number: 40673R and am looking for the spark plug type for the motor. I have an instruction book but it is for a 50hp and up and don't want to chance putting in the incorrect plugs. Thanks for you help.<br /><br />MIKE.N <br />

 

[rickdb1boat]

Re: Spark Plugs for 40hp Evinrude

J4C gapped at .030 Champion Plug<br /><br /> web page

 

[rogerrabbitis]

Re: Spark Plugs for 40hp Evinrude

Thanks.....vary much for the info...hopefully this sunday I'll get the boat out of the water I had a J8C Plug in the motor. and it was not running vary well and the motor could not pick my boat out of the water...hopefully this weekend it will...thanks again..

 

[rickdb1boat]

Re: Spark Plugs for 40hp Evinrude

The J8C is just a hotter plug. Best to use what's recommended, but it may or may not solve your problem...

 

[rogerrabbitis]

Re: Spark Plugs for 40hp Evinrude

ya Well the motor has been sitting for at least 2 years and I have cleaned up the Carb (it was pretty messy) I started it up yesterday and it seem to work better except a little Back firing (With the J4C plug) witch it has not done before and the adjustment for the Lean and rich control started working last time it was out I moved that and it would not do any thing to change the motor behavior. We had it at WOT and it just would not pick the boat up on to plane. We did have 4 people in the boat but when we dropped down to 2 people and we were making "S" turns it all most sounded like it was going to do it. I just have a 14Ft Runabout fiberglass I don't think it is to much weight for the motor. The other thing that was pointed out to me is how much the Prop goes underneath the Boat would make a difference..??. ON the other motor I had on the boat it went a lot lower under the bottom of the boat the person also had one of those hard rubber fins on the motor witch I guess helps it get the Boat out of the water faster so I put that ON the new motor I am trying it out again tomorrow so Wish me luck…thanks for your help.

 

[rickdb1boat]

Re: Spark Plugs for 40hp Evinrude

Did you dismantle the carb and clean it and use a rebuild kit on it. using carb cleaning fluid and compressed air to blow out the passages? Could be there is still gunk in their causing your problem. The backfiring is due to a lean mixture at idle. Back out the idle mixture screws 2 full turns from a lightly seated position and see if this hels. If backing out the idle mixture screw has no effect on the motor, something is clogged or a float is set wrong. The Cavitation plate on the motor should be level or just above the bottom of the stern. A 40 HP would be hard pressed to plane out a loaded boat(4 People). The other thing would be the pitch of the prop. If it's too high, you will never get it to pop out of the water. If the motor is set too low, same results. Do you know what pitch you are running? You may have to have 2 props. One for running with a load nad one for normal running. Do you have a Tach. on the motor? If so, what is your top RPM reading at full throttle? Try having people sit up front and trim the motor in when you take off. A fin will help it plane out faster, but motor height must be correct before real benefits can be had. Trim tabs are another option for your boat and are not that expensive. Let us know how it goes. Might try J6C plugs and gap them at .040 instead of .030. But I would stay away from the J8c's..<br /><br />Motor Height:<br /><br />

 

[rogerrabbitis]

Re: Spark Plugs for 40hp Evinrude

I did not use a re-build kit on the Carb...but will see how it works and than go to the next step....I am using it tommarrow..(Sunday june 20th)...so wish me luck and I'll tell you how it goes...thanks for the info and the help..<br /><br />MIKE.N

 

[rogerrabbitis]

Re: Spark Plugs for 40hp Evinrude

I Tried it today and the motor sounded better and rpm's at slow speed were good but when trying to open the throttle right up the RPM’s seemed to be lacking. (It seems to be running like a 20HP rather than a 40HP)..changing Plugs to the j6c plugs did not change the behavior of the motor so I am thinking I am going to have to get a carb kit and give it a really-really good cleaning I don't think any thing like Timing could affect this and I have no idea how to check timing on a boat motor..??? I don’t have a tach on the motor and I have an extra prop for the motor but both seem to be the same but may try to switch them next time. Thanks for the advice..<br /><br />Mike.N

 

[rickdb1boat]

Re: Spark Plugs for 40hp Evinrude

(It seems to be running like a 20HP rather than a 40HP

Do you have good spark on both cylinders? Is the timing plate advancing fully at full throttle? Have you done a lync and sync? Checked compression? You may want to consider getting a good manual that will explain alot of it.<br /><br /> Factory Manual

 

[rogerrabbitis]

Re: Spark Plugs for 40hp Evinrude

I have good spark on both cylinders and the timing plate is advancing fully at full throttle and the link for the carb at full throttle is fully down I had a little problem with the throttle cable but that is all adjusted correctly now and will Start and stop on command. I am going to have to check compression Any Idea what kind of numbers I am looking for when it comes to that..??...I am going to see about getting a manual for the motor the only one I have here is for 50HP and above....