Logo
FULL SITE MENU

What should the compression be on a 25 hp mariner 1991

S

SAM9993

New member
I have 90 psi in both cylinders a have fuel i have spark but it will not start using a automtive spark tester the spark with jump a gap of almost 3/8 of a inch any ideas
 
90 is OK. Especially if you didn't hold the throttle wide open.
I'd look at the Needle Valve. Sometimes people us Stabil etc over a time and the Rubber tipped Needle valve will stick inside the seat.
Try this, disconnect the line from the pump to the top of the Carb.
Blow in that line. The force from your lungs should force that needle open.
If not, you'll have to take the Carb off, then the top off, to see if that's the problem

When you spray gas into the Carb, does it show any improvment at all? An extra burble or one cylinder try to start?

One more thing to check is the timing of the flywheel. Maybe you've sheared a Woodruff Key and the Flywheel is out of phase with the Crank.
 
thudpucker said:
90 is OK. Especially if you didn't hold the throttle wide open.
I'd look at the Needle Valve. Sometimes people us Stabil etc over a time and the Rubber tipped Needle valve will stick inside the seat.
Try this, disconnect the line from the pump to the top of the Carb.
Blow in that line. The force from your lungs should force that needle open.
If not, you'll have to take the Carb off, then the top off, to see if that's the problem

When you spray gas into the Carb, does it show any improvment at all? An extra burble or one cylinder try to start?

One more thing to check is the timing of the flywheel. Maybe you've sheared a Woodruff Key and the Flywheel is out of phase with the Crank.
Click to expand...
Thank you I will check these out
 
I have tried starting fluid it does nothing I have sprayed gas mix into carb nothing I have put in fuel into spark plug hole still nothing I am at a loss
 
You have spark and fuel, do you have spark at the right time?
How did you check that Key?
You have to pull the flywheel off to check that key.
 
Yes it could.
I'd forgotten I had to buy one of those potted Electronic packages for mine. It was over $100 back in 98 or so.
It's hard to trouble shoot. I dont recall what I did to verify it was that Module.
I dont know where to send you for that kind of Information either.
 
SAM9993 said:
I have 90 psi in both cylinders a have fuel i have spark but it will not start using a automtive spark tester the spark with jump a gap of almost 3/8 of a inch any ideas
Click to expand...

Thanks to all of guys for the input about my 25 hp mariner motor it end up being the bottom silicone gasket on the reed valve and that is part of the reed valve $100.00 later it runs like a watch. I went back to my automtive back ground no vaccum no start.

Thanks to all of you Bill
 
Back
Top