76 Evinrude 15 Not getting Top end RPM

[bktheking]

New- Coils, wires, plugs (the correct ones for points motors), condensors , points, upper and lower crank seal, intake gasket, head gasket, carb gasket, thermostat. Motor is 100psi on both cyinders, starts third pull, pumps water like a garden hose.

Boat is a 14ft Crestliner, weighs 150 lbs- top speed I got was 14mph with 2 of us in the boat.

All the research I've done say that guys are getting 20+ mph with 2 of them in the boat, close to 30 with one in the boat. Transom height is good, I've played with 3 different hole settings, none make a difference. I've checked the carb to mag plate timing- bang on. I felt some play in the mag, I peened the plate and replaced the fibre washer which by the way helped "big time", the old one was wore out. Not a mm of play anymore, points were set to .020. I compared other 15's, mine is missing around 1000RPM compared to the ones on youtube, I know this motor has more.

I pulled the carb tonight, checked the high speed orifice, clean as a whistle and the correct # 58 plug is in the carb. The only thing I didn't like was the old cork float. I put it in carb cleaner as a test and it floated but not all that well. Could the old cork float be causing my issue, it just feels heavier than the new style, if anything you'd think it would have the opposite effect.

I'm at a loss....thanks as always

 

[bktheking]

Re: 76 Evinrude 15 Not getting Top end RPM

Think I figured it out, will know more tomorrow.

 

[Rick.]

Re: 76 Evinrude 15 Not getting Top end RPM

I'm running my 15 on a 14 foot and your speed isn't all that different than mine. Last time out there were three adults in the boat and lots of tackle and we couldn't get more than about 11.5 mph on the lake. With me and two grand kids we go about 17 or 18. Maybe mine is slow, I don't know as I've never checked the rpm at full throttle. It just seems to me that top speed is often exaggerated compared to what I get and that holds true for my 15, 9.9 and 9.5. Anyway, as always, best of luck and I know we can count on you to let us know what you find. I only wish more would follow up instead of leaving me wondering. Rick.

Edit: I can't help but laugh at your comment about I think I found it. It reminds me of a joke I heard a long time ago. "How do you keep an a__hole in suspense? I'll tell you tomorrow."

Well I guess I'll wait until tomorrow.

 

[bktheking]

Re: 76 Evinrude 15 Not getting Top end RPM

I'll tell you now. What I did was update the part with the roller and linkage to the newer black style with the adjustable hex screw for idle instead of the smaller roller with the white style which has that little spring that connects to the starter lockout. What I noticed- at WOT the butterfly in the carb actually goes too far and causes the butterfly to close in the opposite direction. I think it all has to do with with the cam, which obviously changed with the later CD ignition. It was more of an experiment to see if it would work, I'm thinking it caused more harm than good

 

[griggsb]

Re: 76 Evinrude 15 Not getting Top end RPM

Can the carbuerator be synchronized with the timing? I know they ar 2 completly differnt motors, but my Evinrude 9.5 had a bad miss in it. I read the synchronization part in manual. The relationship of the butterflies, to the timing was off. I adjusted it according to the book, and WOW. What a difference. Did you change the timing cam from a CD ignition motor? Just tring to repay you for helping with my 50hp 'rude.

 

[Rick.]

Re: 76 Evinrude 15 Not getting Top end RPM

I'll tell you now. What I did was update the part with the roller and linkage to the newer black style with the adjustable hex screw for idle instead of the smaller roller with the white style which has that little spring that connects to the starter lockout. What I noticed- at WOT the butterfly in the carb actually goes too far and causes the butterfly to close in the opposite direction. I think it all has to do with with the cam, which obviously changed with the later CD ignition. It was more of an experiment to see if it would work, I'm thinking it caused more harm than good

Well I hope your right. Seems to me it would run at top speed with a tiny bit less than full throttle if I'm following you correctly. It seems like I always wish every motor had just a little more speed so I have it at full throttle and then try to twist a wee bit harder. Maybe the trick is to twist a wee bit less! Rick.

 

[bktheking]

Re: 76 Evinrude 15 Not getting Top end RPM

Can the carbuerator be synchronized with the timing? I know they ar 2 completly differnt motors, but my Evinrude 9.5 had a bad miss in it. I read the synchronization part in manual. The relationship of the butterflies, to the timing was off. I adjusted it according to the book, and WOW. What a difference. Did you change the timing cam from a CD ignition motor? Just tring to repay you for helping with my 50hp 'rude.

It is setup as best as can be. I didn't change the timing cam as they are held on different, the older style used bolts, the newer didn't. I'm headed out at noon to get a carb kit. If the kit and switching back to the old style doesn't work I'm almost tempted to change the entire setup to CD but I'm pretty sure the butterfly half closing at full throttle would do it

 

[bktheking]

Re: 76 Evinrude 15 Not getting Top end RPM

Well I hope your right. Seems to me it would run at top speed with a tiny bit less than full throttle if I'm following you correctly. It seems like I always wish every motor had just a little more speed so I have it at full throttle and then try to twist a wee bit harder. Maybe the trick is to twist a wee bit less! Rick.

I wouldn't if the sync was off, advance wouldn't be all the way with the butterfly open full, I think that's what is happening now

 

[bktheking]

Re: 76 Evinrude 15 Not getting Top end RPM

Put the kit and swapped the linkage, me and my buddy who is way heavier than the wife, 14mph, 18 mph just me. I'm starting to think that this is on par. I think guys who say they have their buddies and gear and a 14ft v hull with a 15 evinrude and pull 25mph are full of crap or adding 5 for bragging purposes. The boat is a 60's Crestliner so i'm thinking it's a bit heavier than the new boats, i'll live with it.

 

[ChrisAG]

Re: 76 Evinrude 15 Not getting Top end RPM

With just me (I weigh 150lbs) my 14" Starcraft Sealite goes 24mph - 1978 Johnson 15. It still planes easily with three adults but I haven't measured the speed under those conditions.

Have you fiddled with the trim? Maybe even put a 1" strip of wood on the top edge of the transom where the motor sits. I've noticed these engines have a slightly longish shaft for 15" - my transom is exactly 15" and yet the cav plate is almost two inches below the keel. Can't be great for hydrodynamic drag.

 

[bktheking]

Re: 76 Evinrude 15 Not getting Top end RPM

I will check it out, I know the plate is an inch or so below the keel.

 

[bktheking]

Re: 76 Evinrude 15 Not getting Top end RPM

1 3/4" below to be exact, measured tonight. I'm having a jack plate made to raise it up, fingers crossed.