WOT Problem

[bandit790]

I have a 1974 Evinrude 135hp outboard that I have recently rebuilt the carbs and installed a new fuel pump. After putting the boat in the water it ran fine for a while until I changed fuel tanks. I had a hard time at WOT. I thought that I might of had the oil mixture too rich in the fuel. I took the boat back out several days later and ran it for 1.5-2 hours and had no WOT at all. If the jets on the carb were clogged by too much oil in the gas wouldn't it have cleared-up by then? Another question is that I noticed the plunger in my choke assembly keeps coming out to far and ends up mostly out and diagonal instead of vertical. Can this effect WOT? Any other ideas would be appreciated. Thanks.

 

[jtexas]

Re: WOT Problem

Doubtful you could block your carb jets with too much oil.

If the choke plates aren't open completely that would affect your speed. Do take the airbox cover off & check that out first.

 

[bandit790]

Re: WOT Problem

Doubtful you could block your carb jets with too much oil.

If the choke plates aren't open completely that would affect your speed. Do take the airbox cover off & check that out first.

Choke plates are opening completely at WOT. Everything else looks right too, at least to the untrained eye. If I have an ignition problem shouldn't I notice a rough idle and/or miss at operating speed?

 

[jtexas]

Re: WOT Problem

I'd think you could notice a hi-speed misfire, although if a cylinder is dropping out completely it would be harder to detect.

The current status is, it's not reaching it's full RPM's at WOT, but starts and runs fine otherwise, correct? If you have a tachometer it would be helpful to know what RPMs you usually get at WOT vs. what you're getting now.

Easy stuff first:

Were you using fresh fuel?
Is the fuel line holding pressure?
Make sure the fuel tank vent is open.
If you're using built-in tanks, check the anti-siphon valve.
Check the screen filter on the fuel pump inlet.

Inspect all your fuel fittings, listen for the sound of sucking air while you pump the primer bulb. If they're a few years old wouldn't hurt to replace 'em anyway, they're not too expensive and they do wear out eventually.

Same with the primer bulb, I recommend spending the extra $7 or so for the OMC brand, the cheap bulbs aren't known for reliability.

Also check the fuel pump vacuum pulse line to the manifold.

On the starboard side under the flywheel the timer base is linked to the throttle linkage, it advances the spark timing as the throttle is advanced. With the engine off, get a helper to move the throttle forward - rotate the flywheel clockwise as it shifts into forward to mesh the gears - observe whether the timer base moves smoothly without sticking through its whole range of motion. It hits its stop before WOT. Also it should start moving just before the carb throttle plates start to open.

Check to be sure that the throttle plates are parallel and end up horizontal, but not beyond, at WOT.

You have a new fuel pump, but it wouldn't hurt to check it by pumping the primer bulb at WOT, see if it has any impact on RPM's.

keep us posted.

 

[bandit790]

Re: WOT Problem

I'd think you could notice a hi-speed misfire, although if a cylinder is dropping out completely it would be harder to detect.

The current status is, it's not reaching it's full RPM's at WOT, but starts and runs fine otherwise, correct? If you have a tachometer it would be helpful to know what RPMs you usually get at WOT vs. what you're getting now.

Easy stuff first:

Were you using fresh fuel?
Is the fuel line holding pressure?
Make sure the fuel tank vent is open.
If you're using built-in tanks, check the anti-siphon valve.
Check the screen filter on the fuel pump inlet.

Inspect all your fuel fittings, listen for the sound of sucking air while you pump the primer bulb. If they're a few years old wouldn't hurt to replace 'em anyway, they're not too expensive and they do wear out eventually.

Same with the primer bulb, I recommend spending the extra $7 or so for the OMC brand, the cheap bulbs aren't known for reliability.

Also check the fuel pump vacuum pulse line to the manifold.

On the starboard side under the flywheel the timer base is linked to the throttle linkage, it advances the spark timing as the throttle is advanced. With the engine off, get a helper to move the throttle forward - rotate the flywheel clockwise as it shifts into forward to mesh the gears - observe whether the timer base moves smoothly without sticking through its whole range of motion. It hits its stop before WOT. Also it should start moving just before the carb throttle plates start to open.

Check to be sure that the throttle plates are parallel and end up horizontal, but not beyond, at WOT.

You have a new fuel pump, but it wouldn't hurt to check it by pumping the primer bulb at WOT, see if it has any impact on RPM's.

keep us posted.

Took it out to the lake this evening and fired it up. It ran ok except for no WOT. I have all new fuel tanks, bulb, lines, fuel pump, and rebuilt carbs. The timer base appears to move all right. I'm about ready to give up on this darn thing. Is there anything I could have screwed-up while moving the various throttle/mechanical arms around?

 

[jtexas]

Re: WOT Problem

don't make an anchor of it just yet...

Keep in mind that just because a component is new doesn't mean it's functioning properly.

Your motor needs fuel, spark and compression to run. And timing.

Your symptoms started when you switched tanks. Did you replace the tanks before or after that?

Do a compression test, post the results.
Do a spark test, set the tester for 1/2".

Compression gauge, about $25, spark tester, couple bucks at auto parts store.

Need help with these, just ask.

Have a timing light? Check the timing - search the board for Joe Reeves WOT Timing procedure - you can set the timing without running the engine.

If there's a tachometer on board but it's just not working, let us know, it would be a good thing to have.

 

[bandit790]

Re: WOT Problem

don't make an anchor of it just yet...

Keep in mind that just because a component is new doesn't mean it's functioning properly.

Your motor needs fuel, spark and compression to run. And timing.

Your symptoms started when you switched tanks. Did you replace the tanks before or after that?

Do a compression test, post the results.
Do a spark test, set the tester for 1/2".

Compression gauge, about $25, spark tester, couple bucks at auto parts store.

Need help with these, just ask.

Have a timing light? Check the timing - search the board for Joe Reeves WOT Timing procedure - you can set the timing without running the engine.

If there's a tachometer on board but it's just not working, let us know, it would be a good thing to have.

Both of my tanks are only a few months old. My mechanic told me that the compression checked out OK, but he didn't give me any details. I will check with him tomorrow. I will get the spark tester and timing light tomorrow. Was there anything I could have screwed up by just moving the linkages and arms on the motor?

 

[jtexas]

Re: WOT Problem

yes...but...if it starts good and idles good, and if
the timer base starts moving just before the throttle plates do, and moves all the way to it's stop, and if the throttle plates start out closed, stay parallel and end up perfectly horizontal at WOT, then sounds like you got it back together. And the choke plates are open when they should be open.

One nother thing...find the cam roller on the starboard side of the lower carb - it should align with the upper mark on the throttle cam just as the plates start to open.

Reason I asked when you replaced your tanks is, if it was after your symptoms first started appearing, then you could have got some contaminated fuel. Fuel problem makes more sense considering the sequence of events. Clogged hi-speed jet is still not out of the question, but you want to rule out an ignition fault before opening up the carbs again. And timing. If the spark isn't being advanced far as it should, it won't make as much power as it can.

If your mech gave compression a thumbs up it's probably okay...unless something happened between then and now.

 

[bandit790]

Re: WOT Problem

yes...but...if it starts good and idles good, and if
the timer base starts moving just before the throttle plates do, and moves all the way to it's stop, and if the throttle plates start out closed, stay parallel and end up perfectly horizontal at WOT, then sounds like you got it back together. And the choke plates are open when they should be open.

One other thing that might shed some light on this situation- Just before I started having no WOT I accidentally ran over a bouy wire. There wasn't any damage to the prop, so I thought all was well. I had sporadic WOT for an hour or so after, but then no WOT since. Could that have knocked the timing out of whack or have done something else to cause a similar problem?

One nother thing...find the cam roller on the starboard side of the lower carb - it should align with the upper mark on the throttle cam just as the plates start to open.

Reason I asked when you replaced your tanks is, if it was after your symptoms first started appearing, then you could have got some contaminated fuel. Fuel problem makes more sense considering the sequence of events. Clogged hi-speed jet is still not out of the question, but you want to rule out an ignition fault before opening up the carbs again. And timing. If the spark isn't being advanced far as it should, it won't make as much power as it can.

If your mech gave compression a thumbs up it's probably okay...unless something happened between then and now.

 

[bandit790]

Re: WOT Problem

yes...but...if it starts good and idles good, and if
the timer base starts moving just before the throttle plates do, and moves all the way to it's stop, and if the throttle plates start out closed, stay parallel and end up perfectly horizontal at WOT, then sounds like you got it back together. And the choke plates are open when they should be open.

One nother thing...find the cam roller on the starboard side of the lower carb - it should align with the upper mark on the throttle cam just as the plates start to open.

Reason I asked when you replaced your tanks is, if it was after your symptoms first started appearing, then you could have got some contaminated fuel. Fuel problem makes more sense considering the sequence of events. Clogged hi-speed jet is still not out of the question, but you want to rule out an ignition fault before opening up the carbs again. And timing. If the spark isn't being advanced far as it should, it won't make as much power as it can.

If your mech gave compression a thumbs up it's probably okay...unless something happened between then and now.

One other thing that might shed some light on this situation- Just before I started having no WOT I accidentally ran over a bouy wire. There wasn't any damage to the prop, so I thought all was well. I had sporadic WOT for an hour or so after, but then no WOT since. Could that have knocked the timing out of whack or have done something else to cause a similar problem?

 

[bandit790]

Re: WOT Problem

don't make an anchor of it just yet...

Keep in mind that just because a component is new doesn't mean it's functioning properly.

Your motor needs fuel, spark and compression to run. And timing.

Your symptoms started when you switched tanks. Did you replace the tanks before or after that?

Do a compression test, post the results.
Do a spark test, set the tester for 1/2".

Compression gauge, about $25, spark tester, couple bucks at auto parts store.

Need help with these, just ask.

Have a timing light? Check the timing - search the board for Joe Reeves WOT Timing procedure - you can set the timing without running the engine.

If there's a tachometer on board but it's just not working, let us know, it would be a good thing to have.

I can't find the "Joe Reeves WOT Timing procedure" anywhere on the board. Is there any chance that I can talk you into sending me a copy?

 

[jtexas]

Re: WOT Problem

A prop strike? Not sure what it could do that only affects high speed operation. An impact could knock something out of whack, though.

The search feature has been screwy ever since they "upgraded" the board, I'll look around for the timing article.

 

[bandit790]

Re: WOT Problem

I want to thank all of you for your help. I now have WOT. Now I have two new problems. The first is that it takes forever (1-2 minutes) for it to rev up to WOT. I also have a problem starting it when it's warmed-up. It starts fine when cold. Any ideas?

 

[Theoutdoorsman]

Re: WOT Problem

What did you find as a "fix" for the WOT problem? Maybe you should start there.

 

[bandit790]

Re: WOT Problem

My throttle cables were not adjusted properly. It was not opening up all the way.

 

[Theoutdoorsman]

Re: WOT Problem

Sounds as though another link and sync might be in order after removal, cleaning, and reinstalling the carbs? If done correctly, the cable not being adjusted correctly wouldn't be an issue. I'd tripple check it before moving any further. Maybe someone here can give you some specific instructions as to what you need to do to get this right. Do you have access to an OEM Service Manual? Refer to the following link to get some helpful insight on the WOT and how to build your own spark tester.


http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=28;gtid=1167985

 

[bandit790]

Re: WOT Problem

Sounds as though another link and sync might be in order after removal, cleaning, and reinstalling the carbs? If done correctly, the cable not being adjusted correctly wouldn't be an issue. I'd tripple check it before moving any further. Maybe someone here can give you some specific instructions as to what you need to do to get this right. Do you have access to an OEM Service Manual? Refer to the following link to get some helpful insight on the WOT and how to build your own spark tester.

OK, but if you had to guess what may be causing the slow acceleration curve what would it be? If you have an idea, would this cause difficult warm starts?

 

[Theoutdoorsman]

Re: WOT Problem

Not sure on the warm starting issues, but the slow acceleration curve might suggest a cylinder dropping out. What is your current RPM's at WOT verses what you where running prior to these problems? You did perform a compression and spark test to insure, for yourself, that everything is OK........... right?