75" Stinger 75HP Doggie on take off.

[LIGHTFOOT]

I have a 1975 Johnson Stinger 2 75 HP on a 15 foot Tri-Hull boat. Wants to stall when put into gear, and is very sluggish coming out of the hole. Could never pull a tube or skier with it. Has 110 psi on all 3 cylinders (using testing methods listed on this site) and good spark to all 3. Runs great at high speeds and from about half throttle up to full has plenty of power. Its just very weak at low end and lower speeds. Any suggestions would be greatly appreciated.

 

[TJShag13]

Re: 75" Stinger 75HP Doggie on take off.

What size prop do you have on the motor?

 

[LIGHTFOOT]

Re: 75" Stinger 75HP Doggie on take off.

Don't know, however I replaced the prop with the factory replacement myself using the engine manufacturer, year and horse power when ordering it.

 

[Daviet]

Re: 75" Stinger 75HP Doggie on take off.

Did it preform the same way with both props?
If so, it might be time to overhaul the carbs.

 

[LIGHTFOOT]

Re: 75" Stinger 75HP Doggie on take off.

Its a 131/2x17 prop. And yes, same poor performance as before.

 

[LIGHTFOOT]

Re: 75" Stinger 75HP Doggie on take off.

Side note-- I took it out yesterday and it wouldn't even start when in the water, but ran fine at home on the muffs. I'm confused?!

 

[Daviet]

Re: 75" Stinger 75HP Doggie on take off.

Might be time to overhaul carbs.

 

[LIGHTFOOT]

Re: 75" Stinger 75HP Doggie on take off.

Might be time to overhaul carbs.

I think you're right as it wanted to "load" up at lower speeds anyway.

 

[LIGHTFOOT]

Re: 75" Stinger 75HP Doggie on take off.

Just spoke to a local outboard mech and he thinks it may be a lower end problem. Any thoughts on that?

 

[Daviet]

Re: 75" Stinger 75HP Doggie on take off.

Unless the lower unit is seized and not allowing the engine to turn over, I don't see how it could cause the problems you have described.

 

[LIGHTFOOT]

Re: 75" Stinger 75HP Doggie on take off.

Unless the lower unit is seized and not allowing the engine to turn over, I don't see how it could cause the problems you have described.

THANK YOU! That makes me feel better

 

[LIGHTFOOT]

Re: 75" Stinger 75HP Doggie on take off.

UPDATE- Had the carb's rebuilt and the water pump replaced by a certified marine tech. He checked out the engine as well while he had it. Compression was 135, 133 & 138, spark was good, timing was set at 17 degrees. He tested lower end for leaks (none found).

Took it out today for the first time since at the shop. Pretty much the same result- it will stay running when put into forward but still stalls when put into reverse. (Ever try launching and docking a big heavy boat without reverse?). Its so doggie you wouldn't believe it unless you seen it. Takes about 300 yards to get up on plane. Runs out good at WOT but still seems labored.

Needless to say I'm about to scrape the MC numbers off the boat, pull the drain plug and waive Good-Bye to this 350 pound orange anchor. It has a 13.25X17 prop on it. Does anyone think this may be too big, or have the wrong pitch? Any advice would be great-- I'm at whits end!!! Thanks.

 

[Tim Frank]

Re: 75" Stinger 75HP Doggie on take off.

Any chance the hull is waterlogged?
Symptoms seem consistent with that.

Can you access any of the interior foam to check condition?

 

[LIGHTFOOT]

Re: 75" Stinger 75HP Doggie on take off.

Any chance the hull is waterlogged?
Symptoms seem consistent with that.

Can you access any of the interior foam to check condition?

Yes, its open under in the front and is dry. I wonder if its dropping a cylinder under a load. Is that a possibility?

 

[Tim Frank]

Re: 75" Stinger 75HP Doggie on take off.

Yes, its open under in the front and is dry. I wonder if its dropping a cylinder under a load. Is that a possibility?

Except that you said:

Runs out good at WOT but still seems labored.

I'd be more worried about the foam toward the rear....if you think about how the boat sits.

 

[LIGHTFOOT]

Re: 75" Stinger 75HP Doggie on take off.

Going back to the shop tomorrow. The mech's going to put it in the water and find out what the hecks wrong with it.

 

[ckraker]

Re: 75" Stinger 75HP Doggie on take off.

I'm having almost identical problems on my 1974 135 HP. Let us know what the mechanic comes up with.

 

[LIGHTFOOT]

Re: 75" Stinger 75HP Doggie on take off.

Just got the boat back from the shop. The mech told me that the piston skirts are worn and though it has 130 plus psi on all 3 cylinders, its the piston skirts that draw the fuel into the cylinders. With them being worn it has some blow-by and is running lean at lower speeds and and under power. Only cure is to have it bored out and new pistons installed. To make it usable, he bored re-jetted the carb so at least it doesn't stall when put into gear.