25 hp johnson problem

[whytehall]

I have a 25hp 1991 tiller OB. It starts and idles great, when I apply the throttle the engine runs very rough like only on one cylinder. After about 10-15 minutes the engine runs great from idle to top speed. Any thoughts?

I have a 25 hp johnson that starts and idles great, it runs terrible when i try to give it throttle. after 10-15 minutes the engine runs great from idle thru full throttle. Please help

 

[fireman57]

Re: 25 hp johnson problem

Welcome to iboats. You have the exact same engine as I do except mine is remote steering. Has it done this since you have had it? the only thing I can think of is that yours has to warm up a bit more than usual. Each engine seems to have it's own quirks. You might do a spark check when you start it up to see if you have a coil that is going bad. usually though they cut out when they get warm. I assume that you are not flooding it when you start. I know I didn't help you much but no one else seemed to have anything to offer either.

 

[tashasdaddy]

Re: 25 hp johnson problem

double posting not appreciated. i would check spark when it is acting up. it only has one carb, so not the carb, as they carb would not be selective to a certain cylinder.

 

[whytehall]

Re: 25 hp johnson problem

I could not find the 1st post after 24 hours and thought it was deleted, sorry for the repost.

 

[whytehall]

Re: 25 hp johnson problem

Would the thermostat cause this kind of problem?

 

[whytehall]

Re: 25 hp johnson problem

I put the boat on the water for the first time this year. I put new gas into the tank prior to my 1st trip. It ran poorly until what I thought was the old gas getting out of the system. It ran great the rest of the day. I have had it out twice since and the same thing happens. Starts very easy, boggs down when i throttle up. I keep adding throttle and backing off until it runs great for the rest of the day.

 

[whytehall]

Re: 25 hp johnson problem

double posting not appreciated. i would check spark when it is acting up. it only has one carb, so not the carb, as they carb would not be selective to a certain cylinder.

I thought the 1st post was deleted (sorry)

 

[whytehall]

Re: 25 hp johnson problem

Welcome to iboats. You have the exact same engine as I do except mine is remote steering. Has it done this since you have had it? the only thing I can think of is that yours has to warm up a bit more than usual. Each engine seems to have it's own quirks. You might do a spark check when you start it up to see if you have a coil that is going bad. usually though they cut out when they get warm. I assume that you are not flooding it when you start. I know I didn't help you much but no one else seemed to have anything to offer either.

It has since I bought it, 1st time I thought it was the old gas getting out of the system. I have had it out 2 times since and the same thing happens, starts and idles great, boggs when adding throttle for the 1st 10-15 min and then runs great all day. THERMOSTAT?

 

[Draven1772]

Re: 25 hp johnson problem

Do a compression test and make sure your cylinders are firing up.

 

[whytehall]

Re: 25 hp johnson problem

Do a compression test and make sure your cylinders are firing up.

Compression is fine!

 

[whytehall]

Re: 25 hp johnson problem

I have a 25hp 1991 tiller OB. It starts and idles great, when I apply the throttle the engine runs very rough like only on one cylinder. After about 10-15 minutes the engine runs great from idle to top speed. Any thoughts?

I have a 25 hp johnson that starts and idles great, it runs terrible when i try to give it throttle. after 10-15 minutes the engine runs great from idle thru full throttle. Please help

Anything, it doesnt seem like a tough question?

 

[tx1961whaler]

Re: 25 hp johnson problem

Hmmmm. Spark plugs? Automatic choke sticking?

 

[whytehall]

Re: 25 hp johnson problem

Hmmmm. Spark plugs? Automatic choke sticking?

It has a manual choke which I played with, it had no affect on the engine. I will replace the plugs as I do noy know how old they are. Someone mentioned the thermostat.

 

[fireman57]

Re: 25 hp johnson problem

You might want to watch your timer base when you first throttle up, it may be sticking until it gets warmed up. Might need to put a little grease on it. Otherwise, I am stumped.

 

[whytehall]

Re: 25 hp johnson problem

You might want to watch your timer base when you first throttle up, it may be sticking until it gets warmed up. Might need to put a little grease on it. Otherwise, I am stumped.

Thanks its worth a try.

 

[fireman57]

Re: 25 hp johnson problem

You might buy a spark checker at autozone or cheap auto parts place for about ten bucks and check your spark on both cylinders when you first fire up and make sure that you have good spark. Engine will run on one cylinder. Spark should be bright blue and not yellow or orange.

 

[whytehall]

Re: 25 hp johnson problem

You might buy a spark checker at autozone or cheap auto parts place for about ten bucks and check your spark on both cylinders when you first fire up and make sure that you have good spark. Engine will run on one cylinder. Spark should be bright blue and not yellow or orange.

I will replace the thermostat and if that doesnt work off to the dealer we go.

 

[whytehall]

Re: 25 hp johnson problem

Thanks its worth a try.

Where is the timer base?

 

[clanton]

Re: 25 hp johnson problem

Look at LAUDO posts, you may have the same problem. Check the ignition system with a meter.

 

[redfury]

Re: 25 hp johnson problem

Where is the timer base?

When you take the cover off, you will see the flywheel and below that is the carb. In between both of these is the timer base. It's a black plastic strip that has a shaft with a plastic bearing that rides on it when you throttle up in gear. The throttle moves the timer base, which moves this bearing and shaft that is hooked up to the throttle. It'll open the throttle relative to the spark advance so you don't bog the engine with too little spark advance. When you go to Wide Open Throttle ( WOT ), that part that rides on the timer base will pull away from the timer base as it is being pushed by another wire since the timing has been advanced far enough that the throttle can be controlled seperate of the timer base. Check the operation of that when it is cold and see if it is operating properly. If you don't know for sure, go out to the lake and watch how it operates when it acts up, and how it operates when it doesn't. If it acts the same way for both scenarios, then it's not an issue with the timer base sticking, etc. ( I have the same motor with tiller )