No power

[Mjd]

I have a1977 85hp v4 Johnson nice and responsive when running on muffs but when I launched had a hard time keeping it started then once under way very rough running and no power could not get smooth rpms out of it recently replaced impeller and added tell tale stream

 

[ezeke]

Re: No power

It's very likely that you are running on less than four cylinders. When the engine has no load on it it will sound fine running on just two.

Get an inductive timing light so that you can nail down the misfire on the running engine if the ignition seems to be the problem.

The V4 Engines in this series have ignition problems that are often found to be caused by poor grounding of the circuits, so start by disconnecting, cleaning and reconnecting the engine wiring. - always disconnect the battery first.

You can usually isolate a carburetor problem by covering the individual throats of the carburetors one at a time with a couple of fingers; if one doesn't make any difference, clean that one.

 

[Mjd]

Re: No power

Thanks I'll try that and let ya know

 

[Mjd]

Re: No power

One thing though is there something I can do to create load other than launching the rig

 

[wilde1j]

Re: No power

Not really, unless you have a proper test tank and a test wheel. However, you can test by backing down the ramp, leaving the boat on the trailer (well secured, of course) and running it up with the LU well in the water.

 

[Mjd]

Re: No power

Thanks I'll try that also is there any type of component under the fly wheel that could hang up and not advance timing like on a I/o drive

 

[Mjd]

Re: No power

thanks for your help i tried what you recommended and i think that i may not be getting any fuel to lower 2 cyl's had unit running on muffs and it thought sounded pretty good boy was i wrong pulled plug wires off and NO change to rpms but i did have strong spark on both sides i assume that im not getting gas from lower carb?? any suggestions on cleaning procedure without throwing mix settings out of whack

 

[ezeke]

Re: No power

The carburetors have fixed high and low speed jets with nothing to adjust and no midrange jets. Just be sure to use new kits and follow the instructions in your service manual.

When you put the carburetors back on, you need to synchronize them.

 

[Mjd]

Re: No power

how and why for sync

 

[ezeke]

Re: No power

how and why for sync

When replacing the carburetors it is nearly impossible to get them back in exactly the same position that they were in before.

The throttle plates need to be fully closed at idle and perfectly horizontal at WOT and they need to move precisely together.

The linkage between the carburetors is adjustable for this purpose.

The choke plates also have to be synchronized in a similar manner.

Synchronization is expained in the first section of your service manual and is a step-by-step process that needs to be done in the order presented in the manual.

 

[wilde1j]

Re: No power

Carb advance needs to be synced with ignition ... see shop manual for procedure.

We're playing the same tune!

 

[Mjd]

Re: No power

thanks for all your help its amazing what two more cylinders wil give you out on the water next problem is now i have fresh gas leaking from hole in the back of the air box (what the front part of carbs mount to there is a hole in lower port side corner connect to a tube going to lower part of power head) it slows down considerably when i disconnect fuel supply line from tank