'78 'rude 6hp WOT concern.

[Saell1]

Long story shorter: Got an ebay engine, took it to local authorized repair guys. They said: replace lower lube, water pump impeller, rebuild carb. I said 'do it.' Picked it up, and they said: 'no need to rebuild carb, good compression, fire.' I was pleased that I saved a C-note.

Took my engine to the boat (26' Sailboat, 6000 lbs), got fresh fuel and oil (50:1) new tank, fired it up.

My engine started after 2 pulls, then quit. I had the choke out, and the temp was about 95. I disenaged the choke, and it ran fine after that. After a short warm up, the twist throttle control was not allowing a smooth idle.

After messing with the slow speed idle adj, it was a bit smoother, but gave some serious misses every now and then.

After five minutes of out of gear running, and some amount of consternation, it shifted easily, and we left the slip.

OK, now comes the WOT issue. After getting clear of the slip, the grip was advanced so that the engine was running about half. When I twisted more, the rpm's did not increase. After a few minutes, while the twist was full 'FAST,' the engine caught a new attitude, and the revs jumped up.

This behaviour(?) repeated over 2 gallons, and about 15 miles of observation. I felt as if the revs never really got up to a rate that would be considered 'redline.'

Questions: How may I measure the rpms on this engine?

Could the prop be an issue?

I looked under the cowling, and found a screw that rode on a cam thingy that affected the actual throttle position, there was room for adjustment.

I want to express my appreciation for everyone that has made this forum possible.

 

[RPJS]

Re: '78 'rude 6hp WOT concern.

My guess would be that you are only running on 1 cylinder, start the motor and then remove 1 plug lead at a time, you should hear a noticable drop in the revs when you pull the leads if you don't it indicates that cylinder has no fire.
If you do find a problem don't worry, the ignition system on this engine is very simple to repair.
The cam roller that opens the throttle plate as you advance the twist grip needs to be set "Link & Sinc" alough this has more effect on your mid range revs than idle and WOT, if you look at the cam you will see 2 marks, advance the twist grip untill the roller lines up between the 2 marks, at this point the throttle plate should just be starting to open you can use the small screw just below the roller to adjust the linkage to get this setting right.

Try pulling the plug leads and post back what you find.

 

[Saell1]

Re: '78 'rude 6hp WOT concern.

Long story shorter: Got an ebay engine, took it to local authorized repair guys. They said: replace lower lube, water pump impeller, rebuild carb. I said 'do it.' Picked it up, and they said: 'no need to rebuild carb, good compression, fire.' I was pleased that I saved a C-note.

Took my engine to the boat (26' Sailboat, 6000 lbs), got fresh fuel and oil (50:1) new tank, fired it up.

My engine started after 2 pulls, then quit. I had the choke out, and the temp was about 95. I disenaged the choke, and it ran fine after that. After a short warm up, the twist throttle control was not allowing a smooth idle.

After messing with the slow speed idle adj, it was a bit smoother, but gave some serious misses every now and then.

After five minutes of out of gear running, and some amount of consternation, it shifted easily, and we left the slip.

OK, now comes the WOT issue. After getting clear of the slip, the grip was advanced so that the engine was running about half. When I twisted more, the rpm's did not increase. After a few minutes, while the twist was full 'FAST,' the engine caught a new attitude, and the revs jumped up.

This behaviour(?) repeated over 2 gallons, and about 15 miles of observation. I felt as if the revs never really got up to a rate that would be considered 'redline.'

Questions: How may I measure the rpms on this engine?

Could the prop be an issue?

I looked under the cowling, and found a screw that rode on a cam thingy that affected the actual throttle position, there was room for adjustment.

I want to express my appreciation for everyone that has made this forum possible.

 

[tashasdaddy]

Re: '78 'rude 6hp WOT concern.

your carb has a fixed high speed jet, and adjustable low speed, you could have a partially clogged high speed jet. you can us a induction timining light with and builtin tach function to test the prms. my manual says 4500 for rpms

 

[Saell1]

Re: '78 'rude 6hp WOT concern.

Long story shorter: Got an ebay engine, took it to local authorized repair guys. They said: replace lower lube, water pump impeller, rebuild carb. I said 'do it.' Picked it up, and they said: 'no need to rebuild carb, good compression, fire.' I was pleased that I saved a C-note.

Took my engine to the boat (26' Sailboat, 6000 lbs), got fresh fuel and oil (50:1) new tank, fired it up.

My engine started after 2 pulls, then quit. I had the choke out, and the temp was about 95. I disenaged the choke, and it ran fine after that. After a short warm up, the twist throttle control was not allowing a smooth idle.

After messing with the slow speed idle adj, it was a bit smoother, but gave some serious misses every now and then.

After five minutes of out of gear running, and some amount of consternation, it shifted easily, and we left the slip.

OK, now comes the WOT issue. After getting clear of the slip, the grip was advanced so that the engine was running about half. When I twisted more, the rpm's did not increase. After a few minutes, while the twist was full 'FAST,' the engine caught a new attitude, and the revs jumped up.

This behaviour(?) repeated over 2 gallons, and about 15 miles of observation. I felt as if the revs never really got up to a rate that would be considered 'redline.'

Questions: How may I measure the rpms on this engine?

Could the prop be an issue?

I looked under the cowling, and found a screw that rode on a cam thingy that affected the actual throttle position, there was room for adjustment.

I want to express my appreciation for everyone that has made this forum possible.

Please pardon my double posting.

OK, there is NO doubt that both cylinders have fire, and that the engine is running on two. I may have failed to make my earlier presentation clear. I have since adjusted the idle at the tiller/engine joint, as well as the screw on the roller riding on the throttle advance cam. There is a procedure outlined in my service manual that refers to various engine RPM's

I have remaining the original two unanswered questions:

1- How may I measure the RPM's on this engine?
2- Could the prop be an issue?

My boat is slow and heavy. My service manual says I have a 7" pitch, yet current web based prop suppliers suggest a 6.5" pitched prop.

I feel as if I must know how to determine the pitch of my current prop, and, MORE importantly, how much difference it may make that I have a different prop.

Thank you everyone who have read and considered my posts.

Steve

 

[Saell1]

Re: '78 'rude 6hp WOT concern.

your carb has a fixed high speed jet, and adjustable low speed, you could have a partially clogged high speed jet. you can us a induction timining light with and builtin tach function to test the prms. my manual says 4500 for rpms

Wow! Thanks for that quick reply,

Right, 4500 to 5500. I suspect that my 6805 is running in the lower part of that range. Is there an additive for my fuel or air intake that may clear the suspected intermittant high speed jet clog?

What do you think about my prop concerns?

Steve