1992 Evinrude 70 seems to be very slow

[eph]

Hi all-
I just purchased a 1970 17' Whaler, with a 1992 Evinrude 70, it has a prop is at 15 degree pitch, and according to the tach max RPM was about 4600. With very little load on the boat, just me, 180 lbs, and 6 gallons of gas, the top speed is about 22 MPH, does this seem right? Everything I am reading is saying this boat should easily hit 30, any ideas? And the engine should be running between 5k-6k WOT.
The previous owner was running both the VRO and a 100:1 premix, I nixed the premix after determining the VRO was working and the last time out there were a few moments of greater power upon acceleration, then it was back to normal.
Thanks-
E

 

[HighTrim]

Re: 1992 Evinrude 70 seems to be very slow

First off, his mixture was way off. 50:1 is the pre mix for that motor.

As you know, you want your WOT RPM to be about 5800. You are well off that mark. I dont believe the issue is with your prop. Are you water logged at all? How is your setup?

I would probably start with a spark and compression test then go from there. You want to ensure that you are firing on all cylinders.

 

[Randybeall]

Re: 1992 Evinrude 70 seems to be very slow

Since you had a few events of normal power on you last outing I would look at fuel. Perhaps water in the gas? Perhaps fuel hoses leaking air in at the joints. Could be that he suspected fuel pump problems and was running the 100:1 premix as an insurance. Fuel pump rebuild could be a wise move. And last thought, make very sure what oil is in the VRO tank. Wrong oil could be pistons seizing in the engine........Not Funny!

 

[tashasdaddy]

Re: 1992 Evinrude 70 seems to be very slow

100/1 is not insurance, it is not enough oil. yes there use to be motors that were run on 100/1, but that was recinded, and the service bulletin said to remove all 100/1 stickers on the motors and run 50/1. agree with HighTrim.

 

[kenmyfam]

Re: 1992 Evinrude 70 seems to be very slow

50 to 1 it is in my book as well.
Just wondering if the 100 to 1 was in case the vro failed for whatever reason so that at least some oil got through ????
Just a thought.

 

[eph]

Re: 1992 Evinrude 70 seems to be very slow

The VRO is working, he was running a premix as an insurance in case the VRO failed. Does not seem to be waterlogged is sitting pretty high in the water. I think I will start with the fuel line, there have been times when the primer ball does not stay full when underway, could the carbs need cleaning? And is there any harm in running a pre mix and the VRO?

 

[kenmyfam]

Re: 1992 Evinrude 70 seems to be very slow

The VRO is working, he was running a premix as an insurance in case the VRO failed. Does not seem to be waterlogged is sitting pretty high in the water. I think I will start with the fuel line, there have been times when the primer ball does not stay full when underway, could the carbs need cleaning? And is there any harm in running a pre mix and the VRO?

Premix and VRO = more oil than you need. If the primer bulb is collapsing then you have most likely a venting problem. If it needs pumping when underway then you have a fuel delivery problem.

 

[Okee Jimmy]

Re: 1992 Evinrude 70 seems to be very slow

Check with your local evinrude dealer, there are a couple of service bulletins for this model motor. One bulletin deals with a cooling modification, and one deals with re-jetting the carbs. They will need the model and serial # and the carb #'s. This combination of boat and motor should run in the high thirties, I would also perform a compression test.

B-2271 3-1-93 calibration change
B-2276 12-1-93 cooling system modification
SBE-2271 4-1-93 calibration change

Hope this helps, Jimmy

 

[ebry710]

Re: 1992 Evinrude 70 seems to be very slow

Premix and VRO = more oil than you need. If the primer bulb is collapsing then you have most likely a venting problem. If it needs pumping when underway then you have a fuel delivery problem.

I agree. The primer bulb collapsing means the fuel intake cannot keep up with the fuel pump causing a vacuum in the bulb.

My Johnson/Evinrude Service Manual (1989 120hp) says use 100:1 mixture in addition to VRO pump in fuel tank during breaking-in and testing VRO system.

 

[eph]

Re: 1992 Evinrude 70 seems to be very slow

All-
The update....started with a carb cleaning, when it was discovered there was more sludge than the East River in the carbs it ended up being a complete rebuild. The engine is running very well now, tops out in the high 30's. The VRO is working well, so I am not premixing.
Thanks for all of the advice.
Eric

 

[kenmyfam]

Re: 1992 Evinrude 70 seems to be very slow

Glad all is now well. Keep an eye to your oil consumption though to make sure you are using "enough" comparing to gas consumption.