Tachometer readings by measuring an engines sound

[WriterCJ]

Re: Tachometer readings by measuring an engines sound

Verify boat speed and RPM's at the first chance you get. That should tell you if the motor is not performing correctly.

Top speed with just me aboard was c. 16kt and has dropped to 10-11kt, some of that could be down to sea conditions, and some of it down to the prop, but I'm thinking that part of it is the engine itself.

I'm not sure what WOT RPM was before but now it's c. 4,300 RPM as far as I can tell with the tools I have available. That seems a little on the low side.

While you are out, try pumping the fuel hose primer bulb and see if the engine speeds up.

Tried it last time I was out after reading another thread. Bulb stayed firm and pumping had no effect, so guess that means the fuel pump is OK.

After that test, try engaging the choke/carb primer while it is bogging and see if that has any affect on the engine. If yes, that would indicate trash/blockage of the high-speed carburetor jet.

Thanks, I'll try that next time I'm out -- weather has taken a turn for the worse here... perpetual rain for the last couple of days :-(.

You may be able to squeeze out a few more horsepower with a carb/manifold swap. I'll look for that thread and add it later. Good luck!

Thanks again -- I've read a couple of threads about how the only difference between the 20 / 25 / 30 HP engines from around that time was some parts in the carb (orifices and jets) and the size of the opening in the inlet manifold... could be worth a bit of research and a possible project over the winter.

Thanks again for all your help!

 

[WriterCJ]

Re: Tachometer readings by measuring an engines sound

So I bought one fro Actron with a digital readout on the back. It came with settings for 2/4 stroke and a Tach. It was a 100 bucks.

Thanks... is a timing light something I'd need / would use regularly, or just occasionally? We don't have Actron here in Ireland, but I'll look out for something similar.

Cheers,

Calvin!

 

[Willyclay]

Re: Tachometer readings by measuring an engines sound

Top speed with just me aboard was c. 16kt and has dropped to 10-11kt, some of that could be down to sea conditions, and some of it down to the prop, but I'm thinking that part of it is the engine itself.

I'm not sure what WOT RPM was before but now it's c. 4,300 RPM as far as I can tell with the tools I have available. That seems a little on the low side.

I re-read all your descriptions of the prop damage and the maintenance you have performed on your motor. It is hard to believe that slight bit of damage to the prop is causing this problem. You commented previously that the WOT RPM's sounded higher than the current 4,300 measured with your new app thingy. I agree with your thinking the source is the engine. It may not be happy with all that fuel going through it at WOT and trying to push that relatively large boat. The lugging could cause rapid carbon buildup. Have you tried the decarbonization procedure in the FAQ thread? In the USA, ethanol in gasoline causes lots of problems with non-alcohol resistant fuel lines and carburetor floats. Any chance your high-speed jet has some crud in it again?

Hang in there, I know you will fix it. It is usually something simple. Good luck!

 

[keefallan]

Re: Tachometer readings by measuring an engines sound

I don't know how regularly you would use a timing light. But, you definately need one to set timing on an outboard. Its always nice to have one around?!

 

[WriterCJ]

Re: Tachometer readings by measuring an engines sound

I don't know how regularly you would use a timing light. But, you definately need one to set timing on an outboard. Its always nice to have one around?!

Just reading up on the ignition system in the manual I have, and read this in the section relating to my engine:

"Timing is NOT adjustable with a flywheel CD magneto system. The timing is controlled by the point setting."

I'm guessing that means I'd need a timing light only very rarely, if at all. But maybe I'm wrong. The manual I'm using isn't all that crash hot... must try and source the OEM manual if I can.

 

[WriterCJ]

Re: Tachometer readings by measuring an engines sound

I re-read all your descriptions of the prop damage and the maintenance you have performed on your motor. It is hard to believe that slight bit of damage to the prop is causing this problem. You commented previously that the WOT RPM's sounded higher than the current 4,300 measured with your new app thingy.

A closer look at the prop over the weekend has me thinking that the damage is worse than I originally thought -- I've posted a pic in another thread in the prop forum for some input.

Have you tried the decarbonization procedure in the FAQ thread? In the USA, ethanol in gasoline causes lots of problems with non-alcohol resistant fuel lines and carburetor floats. Any chance your high-speed jet has some crud in it again?

I don't think ethanol in the fuel is as much of an issue here -- but will double check. Haven't tried the decarb yet -- did manage to borrow a compression tester and both cylinders register smack on 100psi, so at least that's one thing eliminated.

I've looked around for SeaFoam... but haven't found anywhere in Ireland selling it. I think this is similar though, and will order a canister and do a decarb as soon as I can, see how that works out.

Going to re-do the link & sync procedure too, as watching cam and cam follower as I advance the throttle last time out I'm not convinced I got it right when I replaced the rebuilt carb.

If the sync between the fuel and ignition systems has slipped since I re-fitted the carb could that cause the performance drop I'm seeing?

Oh and yes... I guess there could always be more crud in the high speed jet .

Thanks again for all the help and encouragement. It's much appreciated.

Cheers,

Calvin!

 

[Willyclay]

Re: Tachometer readings by measuring an engines sound

Calvin,

I looked at your Prop thread and it was worse than I imagined. The recommendations they gave you to clean-up the prop as best you can with a hammer and file for the remainder of the season sounds dead-on. Long-term, you can have a prop-shop refurbish it at a different pitch. After you link&sync, the test for high-speed jet blockage will be to warm it up, get underway, move to WOT and then activate the choke/primer and see what happens. If the RPM's increase smoothly and substantially as a result of the additional fuel being dumped in by the choke/primer, then you probably have jet blockage. If it stumbles and slows down, then the jet is probably okay and the motor is reacting normally to the overly-rich mixture. If it does not change, then you may have an inoperative choke/primer. NOTE: If jet blockage is suspected, it needs to be corrected asap because it is leaning out the mixture of fuel AND oil which is how all those lovely roller bearings get lubed. Continued running with reduced lubrication will lead to a catastrophic failure. The decarb stuff in your link sounds good but I prefer the non-aerosol version so I can put some in the fuel tank also.

If none of the current items of attention significantly raise you WOT RPM's, then I agree it is time for a lower pitch prop. The beauty of going that route is if it over-revs, you can throttle back. Good luck with the next phase.

 

[Willyclay]

Re: Tachometer readings by measuring an engines sound

Going to re-do the link & sync procedure too, as watching cam and cam follower as I advance the throttle last time out I'm not convinced I got it right when I replaced the rebuilt carb.

If the sync between the fuel and ignition systems has slipped since I re-fitted the carb could that cause the performance drop I'm seeing?

Yes, the link&sync is critical and could be the source of your RPM drop. The carb's throttle plate must be fully-opened at WOT. FYI, my neighbor's brand-new motor (cannot mention the brand in the E&J forum because it has black paint) did not have fully-opening throttle plates on any of his three carbs and he was not reaching correct WOT RPM's either.

Retarded ignition timing could be hurting your performance also. Any chance you can rent/borrow a timing light and check this item off the list?

Good luck!

 

[WriterCJ]

Re: Tachometer readings by measuring an engines sound

Yes, the link&sync is critical and could be the source of your RPM drop. The carb's throttle plate must be fully-opened at WOT. FYI, my neighbor's brand-new motor (cannot mention the brand in the E&J forum because it has black paint) did not have fully-opening throttle plates on any of his three carbs and he was not reaching correct WOT RPM's either.

Retarded ignition timing could be hurting your performance also. Any chance you can rent/borrow a timing light and check this item off the list?

Good luck!

Thanks for all the info... will try the link & sync procedure again as soon as I get back down to the boat (weather is rubbish here at the moment). Then will take her out and try engaging the electronic primer at WOT, see if RPMs improve. I know the primer is working from earlier tests.

If it's a blocked jet I already know how to dismantle and rebuild the carb, so that's OK.

That said, when I took the plugs out to do the compression check there seemed to be a good coating of oil around the periphery of the plugs (not around the electrode area -- which looked fine -- but around the outer edge). To my novice brain that suggested that if anything it's running too rich, rather than too lean. Or perhaps the fuel oil mixture isn't being burned efficiently in the cylinder because the spark and fuel systems aren't in sync?

The SELOC manual I'm using tells me my 1989 20HP engine employs a Type II CD FlyWheel Magneto Ignition with Sensor Coils.

Under synchronisation (link & sync) it states:

"Timing is NOT adjustable with a flywheel CD magneto system. The timing is controlled by the point setting."

But earlier in the same manual it says:

"Breaker points are NOT used in the magneto capacitor discharge (CD) ignition systems."

Confusing? You bet!

It does have a bit on adjusting the spark advance timing using a timing light and the spark advance screw -- but doesn't tell me where to look for said spark advance screw, or give real detail of how to actually do the job.

Hmmm... any suggestions?

Will try and borrow a timing light and work it out if the steps outlined above don't solve the problem.

Cheers,

Calvin!

 

[Willyclay]

Re: Tachometer readings by measuring an engines sound

Too bad about the weather. Looks like a few more "rainmakers" are lined up west of Cape Verde. Stay tuned! You may run out of summer.

I thought your primer might be good since "hard-starting" was not one of your issues. Agree with you regarding the wet plugs; sounds like RICH condition. Could be the link&sync but my money is on the low WOT RPM's causing the "lugging" condition which does not allow the motor to flow enough air. My take on the ignition timing question is there are no breaker points on the MagCDII ignition system and the only adjustment is for setting Maximum Spark Advance. I do not have any manuals covering your motor but did find some info in a non-factory Clymer manual at a free online public library. Here's the link:

http://forums.iboats.com/showthread.php?t=393281

LOGIN as instructed and drill down to: Small Engine, Marine/Boat Engine, Evinrude/Johnson, Outboard 2-40HP (1973-1990), Condensed Service Data, Linkage Adjustments & Synchronization. There are text and pictures covering your model and ignition system.

Good luck!

 

[WriterCJ]

Re: Tachometer readings by measuring an engines sound

Fantastic link... thanks... that looks like what I need.

Think it would be a good idea to get hold of a proper tacho and a timing light to check / re-set the maximum spark advance.

Thanks again.

Cheers,

Calvin!

 

[Willyclay]

Re: Tachometer readings by measuring an engines sound

Calvin,

I was thinking about you and your motor tonight after exchanging a number of PM's with several forum members trying to verify some info about another old motor, not yours! The end result was I was guilty of passing along bad info provided by another member whom I and many others regard as one of the forum guru's. Point being, we are all human and make mistakes!

In many of my other posts in the forum, I usually disqualify myself as being an "expert" and frequently request experts to post in threads in order to help insure the OP is getting the best advice possible about their issue. FYI, I have never worked as a professional in the marine industry and rely of 50+ years of recreational boating as I attempt to help others.

Since you have relied on my advice, you may want to start a new thread after you complete your testing and can give additional quantified results to help forum members comment on your WOT RPM issue. I apologize if I have sent you down any false paths!

Good luck, mate! Bill