'84 70 HP Johnson Fast Idle

[harthoyates]

I have rebuilt the carbs, did a "link& sink" motor is still idleing at 1500 to 1600 RPM'S The mechanic still says carbs. Does anyone have any other possible solutions? Thanks for your help. I do not want to buy 3 new carbs.

 

[Reggie08]

Re: '84 70 HP Johnson Fast Idle

Is that idling in the water or on the muffs?

 

[harthoyates]

Re: '84 70 HP Johnson Fast Idle

It was on the muffs. Would being in the water make that much difference? Thanks

 

[tashasdaddy]

Re: '84 70 HP Johnson Fast Idle

yes huge difference. the mech should know that, if not find another mech. there is no backpressure on the exhaust, on muffs. your idle has to be set in the water, with the motor in gear, idling. rpms should be 650-750. use the idle speed screw to adjust speed. it will idle higher in neutral, and on muffs.

http://forums.iboats.com/showthread.php?t=253548

 

[Joe Reeves]

Re: '84 70 HP Johnson Fast Idle

As Tash states....... The idle of the engine, depending on the shaft length, on a flushette should be:

20" shaft - 1000 rpm

25" shaft - 1200 rpm

 

[harthoyates]

Re: '84 70 HP Johnson Fast Idle

I put the lower unit in a 55 gal. drum with water. Idle in the drum out of gear was 1100 to 1200. In gear it was 900 rpms It seamed to go in gear with out excessive "clunk" Do you suppose this rpm range would wind up damaging the engine. I have not gotten the mechanic back over with different carbs yet. He is semi retired and has several boats he is working on. He told me that he did a complete "link-n-sinc". He still feels like it's the carbs. Any ideas from any one. I would like to "whoo it up a little more if possible" Thanks again for the help so far. Harold

 

[Reggie08]

Re: '84 70 HP Johnson Fast Idle

Have you tried adjusting the idle adjustment screw?

 

[harthoyates]

Re: '84 70 HP Johnson Fast Idle

The idle screw is to the max as far as slow idle. All adjustments are a low as they all can go. There is something amiss somewhere? Thanks HTY

 

[tashasdaddy]

Re: '84 70 HP Johnson Fast Idle

what about the idle speed screw. if not i think you need to redo the link N sinc.

typing at same time.

 

[harthoyates]

Re: '84 70 HP Johnson Fast Idle

Thanks for all the input from those who tried to help. I decided to go ahead and put the houseboat in the water to really see what would happen to the RPM's. The motor is still idling at 1100 to 1200 RPM's, but when I put the motor in gear it goes down to 850 to 900 RPM's. The shifting in gear sounds ok, no heavy "klunking". The motor ran well on up to 5000 RPM's. It seems to run best about 3000 RPM's. My mechanic has not returned, since he did the link and sinc. I have another mechanic that said he would look at it this weekend. The idle adjust screw is not even touching, so I don't think that is a factor. Again thanks for all the help. I can do simple things on an engine, but this problem has "stumped" me. HTY