15hp Evinrude is acting up!!!

[FishinDave]

Recently converted my 15hp manual start to electric start. I made the conversion simple with no recharge. I used an electric flywheel from the same year, used the same original manual start stator and ran my positive wire from the starter to the battery with a start button in between. I ran the negative from the battery to the bolt that attaches the starter to the block. The motor starts up fine but when I run WOT, it runs for a "short" minute and then bogs down and shuts the motor off. It also did it when I was running WOT and cut back on the throttle to slow down. Adding the electric start may not have anything to do with this but I just wanted to mention it. Also note that it is hard to start the motor after this happens but when I wait a few minutes, it will start right up, run good WOT for a "short" minute and back to bogging down/shut off. Water is circulating and the engine is not running hot and at low speed the motor seems to be running fine. This is a 1988. We are here to pass on knowledge and there is no wrong answer. Any ideas on what you think it is or could be, please let me know. Thanks

 

[Bosunsmate]

Re: 15hp Evinrude is acting up!!!

Undo the battery after you have started to rule out any shorting or anything there.
Since you didnt change the stator you wont have a rectifier and charging coils that can be damaged by not being connected to a battery when the motors run.

What id do is check that your fuel pump is going ok so prime it manually to act as the fuel pump see if that helps or makes it worse.
Id also check that your primer bulb can hold very tight with engine off.
If it doesnt you might have a failing float/seat/needle valve in carb and are getting leak past it at higher rpm and thus thats flooding out the engine- bogging it and making it harder to restart.

You can also try removing the sparks when its bogs down, seeing if they are wet or dry.
Also you can do a spark test when its bogged down and check both cylinders spark. Sometimes when the engine heats up a coil may temporarily fail or something else resulting in no spark. So when it becomes hard to restart if you check spark then you can rule that in or out.

How do you know its not running hot? Water out the telltale means the waterpump is working but if the thermostat is faulty or a poppet valveis tuck or a passage is blocked the engine will heat up all while the waterpump is pumping and tell tale is pissing

 

[Daviet]

Re: 15hp Evinrude is acting up!!!

Did you have the problem before the conversion?
You might also check the high speed orifice to see if it is plugged or restricted.

 

[steelespike]

Re: 15hp Evinrude is acting up!!!

If the motor seems to be laboring like in a heavy weed bed it may be over heating.

 

[FishinDave]

Re: 15hp Evinrude is acting up!!!

Thanks to you all for your help. I have not put a thermo gun to the engine to check heat but the tell tale is not getting hot and the block itself is not getting too hot for the hand. I did not have the problem before the conversion but the motor is starting up and running fine a slow speeds and running great for a few seconds at top speed. I did check the primer bulb to see if it was still stiff after the engine shut off and it was. Also trying to restart the motor after the issue occurs leaves a fuel ring behind the boat as if it is getting fuel but not a good spark. I will still check the fuel pump to be sure. Bosunsmate, I thought about undoing the cables that go from the battery to the starter and I will do that to rule anything out. When you say to rule out a short, are you thinking that when the engine gets to full RPMs, the stator,coil,plug wires or something of that nature may be grounding to the block and going back to the negative side of the battery? Sunday, I will test the fuel pump, inspect carb, test spark and get new plugs, unhook the electric start cables, heat check the block, and if all of this seems to be working properly, I will put the old manual flywheel back on and run it again. The joys of troubleshooting when you could be fishing. LOL Thanks again and I will post results by Monday.

 

[Bosunsmate]

Re: 15hp Evinrude is acting up!!!

Hi, no im not sure what i was thinking then, but if there was a short i suppose in the way electricity seems to do stuff i didnt now it could it may cause other parts to fail, so best remove that as a possibility.

Id still check the rear of the head for heat and spark test immediately after it has bogged down.
Good luck

 

[FishinDave]

Re: 15hp Evinrude is acting up!!!

Update. Motor is running good once I start it with electric start and unplug the starter wires from the battery.