Need help with my evinrude!!

[JumpinJack123]

Ok me and a friend built a small minimax hydroplane. Powering it we are trying to use a 50's 7.5 Evinrude Fleetwin. The motor sat in my garage for around 3 or 4 years after i bought it. so i started it up this weekend after who knows how long since it last ran and this is what i got...

The motor stated up after a few pulls but it has really no power, like it wont rev up very far and seems to leave a bit of oil in the water and smoke quite a bit. Im using the original Pressure tank which states 1/2 pint of oil for every gallon of gas im thinking it may be too much, with the new oils out there... But whith full throttle the boats moves VERY SLOWLY. The prop looks to be in good condition but im just wondering why the power loss and why the massive amounts of smoke and oil in the water.

this is my first marine engine that ive worked on but i have built serveral automobile engines so ive got the basic knowledge, any help or suggestions would be great!

 

[F_R]

Re: Need help with my evinrude!!

Probably running on one cylinder. Remove the recoil starter and the inspection cover off the flywheel and look in to check the coils. They will be no good (cracked) unless they have already been replaced. Those old OMCs are notorious for that.

Mix is 1/2 pint per gallon as it says. Especially if you are going to use it on a hydro. The fuel going through the non-running cylinder is contributing to the slick and smoke. However, it will do that to a lesser extent even when running right.

 

[JumpinJack123]

Re: Need help with my evinrude!!

I think you were on to something! when i pulled of the cover i could see one newish coil and one that was toast. it was all cracked and when i removed it, it turned to dust. Went to the store and got a new one, installed it. Fired up first pull and got some rpm's out of it. she stuttered for a second but im sure thats because the gas wasn't connected and it was burning the residual. the smoke was greatly reduced and it seems no more gas is rushing out. thanks for your help! Its going on the lake tomorrow and afterward ill give an update!

 

[Lodgepole]

Re: Need help with my evinrude!!

Don't overlook the water pump FOR SURE and also points and condencers.

 

[JumpinJack123]

Re: Need help with my evinrude!!

Well bummer, although the engine put out a lot more power than before it still seems sluggish and wont even plane the vessel. i adjusted the low and high knobs to achieve the most power possible but still nothing. the smoke and fuel leaking are gone though so thats a plus. I dont have a fuel pump, its a pressure tank. Im wondering if the carb needs to be torn apart? the points seem to be in good shape.

 

[F_R]

Re: Need help with my evinrude!!

If it is running that well and the carb responds to adjustments, it is OK. Not all boats will plane with 7.5hp. Maybe yours is one of them?

 

[JumpinJack123]

Re: Need help with my evinrude!!

"As to performance, the minimax will plane a 165 lb man up to 15 mph with a 3hp outboard motor. With 10 hp and over, the hull planing area diminishes until minimax becomes air-born and rides upon the motor's cavitation plane."

That was pulled from the plans that i used to build it. Im not saying the 7.5 should be race worthy or even close to it, but i think there should be more. But the motor is 51 years old so who knows!

 

[JumpinJack123]

Re: Need help with my evinrude!!

http://www.svensons.com/boat/?p=HydroPlanes/minimax
Those are the exact plans if anyone is curious.

 

[55'Fleetwin7.5]

Re: Need help with my evinrude!!

Just curious... have you done a compression test? If you have the equipment, make sure to ground the loose boot to prevent sparks and fire... Give it at least 5 good pulls and take a reading... You should definitely be at least 60lbs or more. My 7.5's both register 75 to 80. These guages are not all that precise but at least you would get an idea where you are at.

tc