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1990 evinrude 8 hp miss or surging @ wot

What's wrong with the throttle adjustment? Did the cam follower not go back on properly when you rebuilt the carb? Some pictures of throttle adjustment problems might be helpful.
 
Swarlos said:
What's wrong with the throttle adjustment? Did the cam follower not go back on properly when you rebuilt the carb? Some pictures of throttle adjustment problems might be helpful.
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During this bad weather I took the time to read everything in the tune up section. As suggested, I did or rechecked in order. The roller was way out of position in relation to the cam in the idle position. the cable needed adjustment,the idle adj. on the tiller was clockwise all the way. when you turned the throttle to full speed, the throttle plate was only open 75%. Ran the engine in the tank yesterday after adjustments in gear for 20 min, doesn't run any better, but i'll be able to see if the point where the engine surges, stumbles, misses, cavitates or whatever its doing, gets worse with more of the throttle that was never available before. I'll be back with more. Thanks, JB
 
Well it came down to this. Got out early before the breeze came up. With my wife and I and the new throttle adjustments up on plane wot 17 mph (had no idea b/4 as she had not had the speed app, and I have a flip phone). Still that issue, but no worse. Drooped her off (she told me to go run the boat some more so I wouldn't tinker with it all day). Harder to get the boat on plane with only me on the boat (all the weight in the stern) I have an 8' fuel line which does keep the fuel fwd of midships to help a little. Get her going and up on plane what do you know, no issue, have no idea what speed, but running at a different angle. Can I assume @ this point it is cavitation? I was never able to find videos where you could hear it, only explaining it. Does this mean I need to leave my wife at home? ( she only weighs abt 110#) If that really is the problem, anything to do? Thanks, JB
 
Swarlos said:
Is your motor tilted up too high? How deep is the prop in the water and what kind of boat are you running on?
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The motor sits plumb with the boat in the water, as the transom has a pronounced rake, that's the 4th pin hole from the mounting bracket. The motor's cavitation plate is 1/2" below the boat's bottom, and the tip of the propeller is 1/2" below the cavitation plate. The boat is a 12' aluminum with a 48" beam ( wetted area ). Has a deep vee fwd then flattens out for the last 8'. This is not a hard chine boat. Rounded chine back aft, with a fair amount of tumblehome. As I did these measurements this morning, I wondered that if it wasn't for the transom rake, how would the engine even pick up water for the w/p. Anyway it is what it is, can't change any of the dimensions. Thanks, always appreciative of all the help. Don't know enough about what's right or wrong with these small boats to be able to help myself, JB
 
Try using the closer holes and see what changes that makes in how it runs. The motor shouldn't necessarily be plumb in the water. I use the closest hole on my 14' vhull alum boat with 15hp Evinrude.
 
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Swarlos said:
Try using the closer holes and see what changes that makes in how it runs. The motor shouldn't necessarily be plumb in the water. I use the closest hole on my 14' vhull alum boat with 15hp Evinrude.
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I will try that when the breeze dies out, is it wrong to think that the more you move the lower end fwd
fwd from plumb, it would have the tendency to hold the bow down? Thanks,JB
 
There are tiller extensions you can buy, but they tell you not to use them to go faster than trolling speed. Yes, moving the prop forward will keep the bow down more which will help you get on plane if you have more weight in the stern.
 
Swarlos said:
There are tiller extensions you can buy, but they tell you not to use them to go faster than trolling speed. Yes, moving the prop forward will keep the bow down more which will help you get on plane if you have more weight in the stern.
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Makes sense from a safety standpoint I guess. I'm concerned now abt the few times we were on plane, and I heard the engine loose suction to the w/p ( it wasn't flat calm ) picked it up in a few seconds. I'm disappointed that the boat seems to run better without my wife up fwd, small price to pay, I guess the only thing now, is to adj the position of the motor bracket and see what works best and what a good friend of mine used to say "and that's that". Thanks for all the followups, if I find what works best, I will let you know. Probably have some other questions as things go along, the learning curve is pretty steep. Thanks, JB
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