Boat runs fine on muffs, not in lake 115 johnson

[whitejamie99]

My boat runs fine in the driveway. Starts on 3-4 cranks and idles well. Deosn't get hot and gets up to op tems pretty quick. But when I take it to the lake it wont start or dies after a start. I start it the same way every time and I dont understand. I keep cranking until the battery lost power. There were a few small wisps of smoke coming from the top of the starter???? What could be the difference between the lake and the driveway? Frustrated!!!<br /><br />Jamie White

 

[Pony]

Re: Boat runs fine on muffs, not in lake 115 johnson

Well i think the difference between the lake and the driveway is that on the lake the exhaust has a load against it. Im sure that someone more helpful will come along but it might might be possible that your plugs dont fire or have a weak spark on load...just my two cents as thats where id begin troubleshooting if it were my motor.<br /><br />PS. Dont burn out your starter, easy to do with all that constant cranking

 

[monoshock]

Re: Boat runs fine on muffs, not in lake 115 johnson

I’m thinking you need to set the idle a little higher on the hose before you take it to the water.

 

[whitejamie99]

Re: Boat runs fine on muffs, not in lake 115 johnson

^ bump

 

[ondarvr]

Re: Boat runs fine on muffs, not in lake 115 johnson

What method do you use to start it? in detail. This will help to detrmine cause.

 

[reorx]

Re: Boat runs fine on muffs, not in lake 115 johnson

had some problem found the fuel line was pinched when motor was trimed down.

 

[Walker]

Re: Boat runs fine on muffs, not in lake 115 johnson

What year is your motor. Does it have a choke primer or butterflies choke??

 

[tashasdaddy]

Re: Boat runs fine on muffs, not in lake 115 johnson

the idle on muffs has to be set at about 1000 rpms, to get it to start in the lake. the you need to fine tune the idle, the reason being is there is not back pressure on the exhaust on muffs. read joe reeves post in the engine faq forum on setting the carbs. keep cranking and you'll be buying a starter.

 

[Tacklewasher]

Re: Boat runs fine on muffs, not in lake 115 johnson

had some problem found the fuel line was pinched when motor was trimed down.

With me it's usually that I've disconnected the fuel line while driving and never re-connect it.


but I still haven;t forgotten to put the plug in

 

[reorx]

Re: Boat runs fine on muffs, not in lake 115 johnson

I almost forgot once I took the boat to the launch backed up to the water disconnected the boat from trailer and noticed the plug missing
that sucked had to drive all the way home just to find the plug on the boat fun day

 

[bansheetaz]

Re: Boat runs fine on muffs, not in lake 115 johnson

make sure idle timing is 5degrees. that was my problem with a 73 115 johnson

 

[guywithboat]

Re: Boat runs fine on muffs, not in lake 115 johnson

I would check the compression. It is easy to do and most likely the issue. It was with my old 67' Johnson. Seafoam will help if the cylinders are not too bad.

 

[ezeke]

Re: Boat runs fine on muffs, not in lake 115 johnson

I have to say that idle speed of 1000 RPM is more than I have ever needed on a V4. I would think my gears would last a lot longer at 700-800 neutral idle. I don't have any problem getting there when my motors are running right.

The QuikStart is the exception but it slows right down once it warms up.

I think you may have dropped a cylinder and that the sooner you run the compression test and the spark test, the better.

 

[Tom Scully]

Re: Boat runs fine on muffs, not in lake 115 johnson

What tdaddy is saying is to set the idle to 1000 rpm while running on the muffs, when you put it in the water the idle will drop to 700-800 rpm.

 

[ezeke]

Re: Boat runs fine on muffs, not in lake 115 johnson

You should not be setting anything on the muffs.8)8)8)

 

[Tom Scully]

Re: Boat runs fine on muffs, not in lake 115 johnson

OK then....
On the muffs the engine will normally run at around 1000-1100 rpm.
When you put it in the water, with the engine in it's normal running position, the rpm will drop to around 700-800 rpm due to the pack pressure on the exhaust as a result of being submerged approximately 18-24".