20mph?......Really?

[theviking64]

So I took the boat out on it's maiden voyage yesterday. The engine started great, idled at about 600 rpms. Got it out into open water and dumped the throttle......20 mph at 2k rpm's is all it would do..... In neutral I can rev it to 6k rpms, so I know the carbs are working.....maybe the cable?

 

[194269]

Re: 20mph?......Really?

You don't know the carbs are working. Any engine will rev quite high with out a load and very little throttle. Check your carbs, one or all may be flooding and check your fuel pump.

 

[bouttime007]

Re: 20mph?......Really?

Make sure the butterflies are fully opening while underway, you may need a link & sync.

 

[theviking64]

Re: 20mph?......Really?

Oh man! We are getting into the realm of so not my forte here. I will try these ideas and see what happens. Should I just have the carbs rebuilt? They never have been, they have been cleaned really good, but never rebuilt

 

[bouttime007]

Re: 20mph?......Really?

They may be fine, just need adjusting to get full throttle.

The timing sync with the carbs may be off too, so it wont run to the fullest.

 

[restornator]

Re: 20mph?......Really?

Oh man! We are getting into the realm of so not my forte here. I will try these ideas and see what happens. Should I just have the carbs rebuilt? They never have been, they have been cleaned really good, but never rebuilt

i wouldn't have the carbs rebuilt. You should get a manual and trouble shoot as much as you can before dishing out $100/hr to the mechanic.

 

[ssobol]

Re: 20mph?......Really?

My Yamaha engine will not go above 2K rpm if there is insufficient cooling. Perhaps you have a cooling issue.

 

[theviking64]

Re: 20mph?......Really?

Just replaced the impeller, it's spitting water out great

 

[theviking64]

Re: 20mph?......Really?

I don't wanna shell out $100.00 a hour either. But these carbs have never been rebuilt in the 33 years they have been in service, with alot of that time just sitting..

 

[Chinewalker]

Re: 20mph?......Really?

One thing I would NOT do - don't run it again until you have it sorted out. If a carb is fouled that means the related cylinders aren't getting lubrication and you can cook it in a hurry.

Check for spark in all six holes, check compression, then move onto the fuel system...

 

[boatnut74]

Re: 20mph?......Really?

My 110 'rude was doing the same thing last year, turned out to be the bushing for the linkage to the timer base. It got brittle and fell out. It fits in the half moon slot, just something simple to check out.

 

[archcycle]

Re: 20mph?......Really?

spark, spark, spark.

If you're missing a spark on just one you can still spin the motor fast with no load. Do rebuild the carbs, but also don't be shocked if it's a bad $25 ignition coil that isn't sparking.

 

[Borgey401]

Re: 20mph?......Really?

I don't wanna shell out $100.00 a hour either. But these carbs have never been rebuilt in the 33 years they have been in service, with alot of that time just sitting..

I would have them rebuilt. That's a pretty long time in service not to have them done properly.

 

[iwombat]

Re: 20mph?......Really?

Like chinewalker said . . .

Compression test & spark test first, then move on to fuel issues.

 

[Daviet]

Re: 20mph?......Really?

Do the free stuff first, spark and compression.

 

[lexer440]

Re: 20mph?......Really?

If spark, fuel and timing are not issue check cooling system. If its running too cool, ie thermostats not closing, it will have those symptoms, it has to reach operating temp. You may be able to clean thermostats and refit them to test short term but if bad they will need replacement.

 

[nwcove]

Re: 20mph?......Really?

.......and dont rev it in neutral......to 6000rpms, unless you really want to risk major damage.

 

[Tim Frank]

Re: 20mph?......Really?

.......and dont rev it in neutral......to 6000rpms, unless you really want to risk major damage.

....or 3000 RPM....

 

[theviking64]

Re: 20mph?......Really?

Ok, Has spark, and good compression. Taking it in this week to have the carbs rebuilt.
3 carbs @ $130.00 ea. Seems fair to me. To be continued...............

 

[theviking64]

Re: 20mph?......Really?

18' Aluminum boat, 150 hp 2 stroke motor, I should be able to do this: http://www.youtube.com/watch?v=hSufUWimFHM&feature=related