1971 evinrude 9.5 hp no top end speed goes about 8mph

[kawi027]

Okay im a bit frustrated with my 1971 evinrude 9.5 hp model 9122 R. Heres whats goin on.

Engine runs great in the garage idle and runs smooth...purrs like a kitten.
I take it out to the lake in my 12 ft aluminum flat bottom with just me in the boat and 6 gallons fuel etc, I weigh about 200lbs and the thing goes about 8mph and I can barely get the front end to plane! I have done all the repairs listed below (except the points adjustment) and have already been on the water and they have made no difference whatsoever. Heres what Ive done:

Took the top of the carb off (looked pretty clean) except I noticed a tiny bit of debri in the float bowl (probably from the old float) , so I sprayed out every orifice, removed the high speed jet and sprayed with carb cleaner and blew it and the rest of the carb with air. Also I visual checked out all the fuel lines and did not notice any leaks.

Compression is about 80lbs in both cylinders using the pull rope, check to see if both cylinders were working by removing 1 spark plug at a time (both are running ).

Prop seems fine, this is a short shaft evinrude, I tried different prop angles in the water and nothing helped, even messed with the lean/rich dial...nothing!

I have not checked the reeds yet but I did not see the carb spitting any fuel up and plus the thing sounds great just no power on the top end. When I have it full throttle it sounds like the engine has a lot more RPM to go (and yes I checked the throttle linkage and it is getting full throttle.

I bought this engine a few weeks ago and the old owner said that it had been sitting for about a year because the last time he took it out it overheated on him and was smoking (due to a bad water pump). I took apart the water pump and the set pin had stripped out the old water pump key so I replaced the complete water pump and it no longer overheats.

The only thing I adjusted but have not taken to the lake since I adjusted it were the points, both were set at about .013 so I readjusted them to the correct .020. Also the rest of the ignition system looks pretty new. Since the points were off by this amount would that affect the top end power?, I started it up and the engine sounds about the same when the points were off.

Sorry for the long essay but I wanted to give all u guys as much info as possible. Im heading to Big Bear tomorrow (friday) and would appreciate any quick tips on things I may have missed and could check.

Thanks in advance.

 

[kawi027]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

I oh I forgot I also ran the boat on the water with the engine cover on and off to check exhaust leaks. It made no difference in performance

 

[BonairII]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

Your points are def important. Just replace them.

 

[F_R]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

It is almost guaranteed that your motor is running on one cylinder---EXCEPT you said pulling one plug wire makes no difference. That kills that theory.

The next one is the motor is fried from overheating. But you say it starts and idles fine.

In short, I don't have an answer based on all that you are telling us.

EDIT: Yeah, I do have another thought. Did you (or somebody else) run any drills or wires through the high speed jet? Or replace the part with the wrong one? If running too rich, it certainly would lack high speed power. It should be stamped 48 (.048" orifice).

Also, can we assume the motor is not revving up but not going anyplace? That would be a spun propeller hub slipping>

 

[todd57]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

How about a link and synch? That ensures that the timing is advancing at the same rate the throttle is opening. I would think that would have an effect on top end power. The Throttle shaft should only just begin to move when the cam follower is at the mark on the throttle cam. And your throttle plate should not go past vertical when at wide open throttle.

 

[BonairII]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

Have you tried misting the carb with premix to see if the motor picks up? Could it be possible that you're losing a cylinder as you speed up?

 

[kawi027]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

Supreme u sir are a genius. I pulled out the high speed jet and the previous owner had a 44 (.044)!!!!! Im going up to Big Bear tomorrow and the altitude is about 6500ft, I am in Los Angeles (2000ft). Should I leave the 44 jet in or try to find a size 48 jet?

 

[F_R]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

Sorry, I'm at sea level. I'm ignorant about you mountain guys' problems.

 

[cajuncook1]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

At higher altitudes, there is less O2 so, it would reason that a narrow diameter high jet would be used at a higher altitudes. The high speed jet with .044 orifice would prevent a too rich fuel mix in an environment with slightly less available oxygen O2.

Since your at a lower altitude an appropriate sized high speed jet would be needed because there is more available O2 and the previous jet at .044 would be restricting flow some.

It make sense, because if you have good compression (80psi...great for your motor), functional ignition, and your carburetor is clean and set and you have ruled out exhaust leak issues.

I looked up the standard carburetor orifice was 0.048 inches as documented in the 1971 9.5hp Evinrude service manual

.

I love following F_R's comments.....I always learn something.


kawi027 let us know how it turns out!!! Oh, Lindy had a good comment with pumping the bulb while running wot to see if the fuel pump is functioning poorly.


Couple of comments if I may.

- May sure your fuel tank hoses are in good shape and not cracking or look old. Talking about fuel tank hoses as well as the motors fuel hoses. Air entering the system at WOT may cause a decreased performance.

- Check your fuel pump, to make sure the little screen is not clogged up with debris or slug. The motor will run ok idling and lower speeds but will run suboptimal at top speed.

- Make sure you are using fresh gas and oil mix. Old gas will cause poor performance.

- Make sure you vent cap or screw is open on your tank to allow air to enter the tank. If not you will get poor running performance because the fuel pump is trying to pull fuel from a tank that is building up negative pressure, thus poor fuel delivery at WOT. If you have the metal tank, make sure the little seals on the fuel connectors are not damaged or clogged up.

Good luck

 

[kawi027]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

Okay so went up to Big Bear with the size 44 jet and the boat ran the same as it did at sea level (like crap). We used fresh gas/oil and tried pumping the fuel bulb...nothing helped. It has a new fuel pump and the filter is clean.
I am going to order the factory installed jet size 48 and run the boat at sea level and see if that helps.
Does anyone think there would be a huge difference between a size 44 and 48 orifice in the jet?

Ill give a update once I get the new jet and hit the lake. Thanks again for all the help!

 

[Rick.]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

Did you replace your points yet? Or at least clean and re-gap them? I can't offer much regarding altitude as I don't stray that far from home. Best of luck. Rick.

 

[kawi027]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

Points looked fine (condition wise). I did re-gap them but did not notice much of a difference. Im pretty certain that putting the proper jet size should fix
the problem...hopefully!

 

[Rick.]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

You would be wise to clean the points. Just rules out one potential issue. Rick.

 

[RandyJ]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

I very recently had a very similar problem. Both plugs on my 25 Johnson were firing and I had gone crazy cleaning and messing with carb & points. Finally... I got an old spark plug to build a makeshift spark checker and easily saw a difference in the spark. I changed out the condenser on the affected cylinder then she ran like new... before that it was just as you described, slow and wouldn't get up on plane. Now it JUMPS up on plane.

 

[dave3xr]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

I have the same motor and experienced a very similar problem a couple of years ago. Ran great at idle or even under power in the tub. Had spark at both plugs. But put the motor on the boat and no power. Would run and start good but no power. Eventually replaced the coils for both cylinders and problem gone. The coils were not completely shorted so they still provided spark, but could not produce enough for the demand under higher load. It worked for me anyway and by reading through this thread, the coil looks like the one thing you may not have looked at. Hope it helps.

 

[dave3xr]

Re: 1971 evinrude 9.5 hp no top end speed goes about 8mph

PS to add to the last post, that goes along with the one above, you might as well put in new condensers when or if you do change the coils. They looked fine on mine but for the couple of dollars, I did replace them too. Good luck.