1988 25hp Johnson stalling

[82ndairborne]

Ok, let's just say this is my 2nd boat and 2nd time I'm regretting buying a boat. 88 25hp johnson, first time I took it out it all ran great, previous owner just had a lot of work done to it. Motor will start and run perfect in a test tank, forward reverse idle to top speed no problems. Put it in the lake runs fine in neutral and in gear until you give it throttle, if try getting up to speed for a few seconds then just stalls and falls flat on its face and dies. I'm a mechanic by trade but boats just **** me off lol. Anything you all can give me to check on would be appreciated. I have the manual for it and checked a few things out and everything seems fine, next thing I was considering was going thru the carb. But by the looks of it it was rebuilt, it's clean enough to eat off of. Thanks

 

[flyingscott]

Try pumping the primer ball and see if it improves If it improves look at the fuel pump. You also need to do a spark and compression test also.

 

[jasper60103]

Ok, let's just say this is my 2nd boat and 2nd time I'm regretting buying a boat. 88 25hp johnson, first time I took it out it all ran great, previous owner just had a lot of work done to it. Motor will start and run perfect in a test tank, forward reverse idle to top speed no problems. Put it in the lake runs fine in neutral and in gear until you give it throttle, if try getting up to speed for a few seconds then just stalls and falls flat on its face and dies. I'm a mechanic by trade but boats just **** me off lol. Anything you all can give me to check on would be appreciated. I have the manual for it and checked a few things out and everything seems fine, next thing I was considering was going thru the carb. But by the looks of it it was rebuilt, it's clean enough to eat off of. Thanks

What kind of work did the PO have done on it?
That may offer some clues.

jasper

 

[82ndairborne]

tried the primer bulb, no luck. The PO had all new ignition put on it, topend "redone" whatever that includes I don't know to be honest.

 

[jimmbo]

Is there spark at both cylinders? Check the plugs for fouling. How long as the interval between the 1st time, when it ran great, till now, where it barely runs?

 

[82ndairborne]

Plus look new spark is great on both, 5 days between runs

 

[Newyota]

I know I am on my second outboard also(88 9.9 &85 20 johnson) and have had to work on both right away.I learned do not assume anything!!Try new plugs since they could be fouled even if they said they are new.Plugs are cheap.Fuel pump is a suspect for sure.If it were me I would start over and check everything as if nothing was ever worked on before and go from there such as the linkages to carb.Get started and get a spray bottle of your choosing and spray around intake and carb gaskets for leaks and see if it runs different.Maybe things put together wrong.Watch some youtube videos.Lots on there for these engines.They help me.As a mechanic you have probably seen other bad work by other mechanics or DIYS.I got an 85 20hp last summer which is probably identical to yours in most regards and am learning a lot such as I should of checked gear oil before buying it.Was almost none(maybe 1-2 oz) in gear box when I got it home and I gave top dollar for it.Still sorting it out!Not sure why it would run good in a tank and not on the water?What changes or changed from first run is a mystery I guess?Carb.looks clean on outside or inside.I would pull it off and go thru it.You may want to check the float needle and make sure its is not getting stuck.Go thru slow speed /idle screw adjustments again.

 

[oldboat1]

Anything special happen when you were out running on the first run -- time it ran well? You tested it in a tank to check an issue presumably, unless just flushing.

 

[racerone]

Could be as simple as opening the low speed mixture 1/2 turn.---Or throttle is opening too soon.-----Post picture of the adjustment on the long metal rod that goes to the back of the motor.-----Post picture at slowest idle position.---That is often adjusted because when it is correct it looks wrong !

 

[AlTn]

arrow on the primer bulb pointing towards the engine?...if so...you can pump the bulb to act as a fuel pump just to check that fuel supply isn't the problem