RPM/WOT Evinrude 115 1977

[Dave Abrahamson]

Re: RPM/WOT Evinrude 115 1977

Is 40mph GPS speed or Pitot tube speedometer? Those Pitot speedometers are not very accurate. These guys are pros here, won't be long before they get you all squared away.

 

[ob15]

Re: RPM/WOT Evinrude 115 1977

Lately we have been getting posts with people using Teleflex tachs and the reading have been off. This could explain the drop in rpm. Even taking that into consideration, your rpms are too low. Pay attention to the setup guru Dhadley, he will help you get your rpms up. Not to say anyone else can't help but he is the master. Just take a look at the prop forum & you will figure that out.<br /><br />Dave A has a good point also. Are your readings with a gauge or GPS?

 

[vano6990]

Re: RPM/WOT Evinrude 115 1977

Thanks for the replys. The spedometer is a Pitot tube it think/guadge. It is just based off water pressure. I also have a spinner type tach to my depth finder and that was reading like 43.5 mph. I am not sure exactly what size prop I have. I cannot locate any numbers on it or sizes. I have even taken it off to no result. I am basing the size due to the seller also gave me another prop with the boat. It's size is 13 3/4" x 17pitch nd the diameter is larger and the pitch is less. That is why I keep wondering if I am just running the wrong wheel? And if so what size wheel do I need for the best performance? <br /><br />Dhadley, I did check the setting before instaling the tach and it was set to 6p and I verified just now it is at this setting. Now there were only two wires on the old tach. Didnt seem to have power. I routed power to the p. Then ground/black. Then the yellowish wire to the sender (this was the wire on the other post on the old tach other than the ground). When I put the key in and turn it, the tach pointer drops to zero. It seems to be working but I do not know how to tell if it is not accurate?

 

[vano6990]

Re: RPM/WOT Evinrude 115 1977

Sorry to dobule post, but continued I cannot even try the prop that I know what size it is due to has the wrong size hub sleeve to fit my motor. As for the the wires on the tach. The old one had just yellowish and ground no power connection from the ignition. I put in the new one and ran power from the ignition to the tach to the third post power and then the ground to ground and yellow to sender.

 

[OBJ]

Re: RPM/WOT Evinrude 115 1977

Usually, there is a number on the end of the hub.....the side the prop nut goes on. Nothing here?

 

[vano6990]

Re: RPM/WOT Evinrude 115 1977

Nope! Nothing: unlike the other prop that tells me exactly what size and pitch it is too bad it has the wrong hub sleeve. Can hubs be changed?

 

[MCM]

Re: RPM/WOT Evinrude 115 1977

I'm just curious I quess but in your original post you stated, <br /><br />"I am running a 13&3/4 inch w 15 pitch. Is the pitch wrong?"<br /><br />Where did you get these numbers?

 

[vano6990]

Re: RPM/WOT Evinrude 115 1977

MCM the size is just a guess. As above I have a second one (white) that looks like the pictures of props in my owners manual that came with the motor but has the wrong size hub sleve and wont fit on the shaft?? I do know the prop currently on the boat (black)is smaller in diameter and props arrent at an angle like the White one (size 13 3/4" x 17"). The black ones measurments are no where to be found and just checked again and compared it to the white one and the white one is definately larger in diameter than the black one, but maybe the black one is a 13' x 19"? Sorry about the miss information, I was taking a shot in the dark and guessed. I have only had the boat for a year and never used a motor over 18hp prior. Do I need a new prop even to just start with?

 

[vano6990]

Re: RPM/WOT Evinrude 115 1977

ok, I bought a new prop (13 3/4" x 17"), hub kit, and they will be here March 8. This way I will know what I am running and then start over again with the outcome. Can anyone help me with putting the prop hub kit togather? Or is it fairly simple?

 

[vano6990]

Re: RPM/WOT Evinrude 115 1977

I'm back! I put on the new prop 13 1/4" x 17 pitch (Michigan wheel aluminum prop xhs). The motor ran at 5100 RPM and my speedometer indicates aprox 41 mph. Since this motor is a 1977 should I really try to push it over the 5500 RPM listed in the owners manual as the top of the WOT range. It is a 1977 and I would expect it to run decent due to the condition but at 5600 to 5800 RPM won’t I really be testing the old power train/heads/rods etc? My owners manual indicates the WOT rpm is between 4500 to 5500. Should I just buy a 15 pitch prop and try again to see if now that I know the size prop I am using if the RPM increases at lower pitch? I am working on the compression test. Thanks in advance for any input on my problem(s).

 

[Solittle]

Re: RPM/WOT Evinrude 115 1977

Do the compression test before spending a bunch more $$.

 

[G DANE]

Re: RPM/WOT Evinrude 115 1977

It seems to me your motor is running fairly. Do a compression test.If the numbers are within app 10% from eachother, do a search in FAQ on how to decarb your motor and do the procedure at least twice, if it hasnt been done recently. This is especially necessary when running a tad low in WOT rpms. Make it a rule doing it for every approximately 50 hrs. Cheap insurance for not carboning up your motor. A lot of people think higher rpms are hard on the motor. Actually low WOT rpms are harder to it, if running with full throttle anyway. Its like choosing wrong gear up hill with a manual transmission.

 

[walleyehed]

Re: RPM/WOT Evinrude 115 1977

flathead, in 1977 when that engine was built, it done well at 5500 with 1977 fuel...With todays crap fuel it takes some RPM to get a clean, efficient burn. That engine has no more stress (maybe less) at 5800 than it does at 5500.<br />Run fresh 87 Octane for fuel.

 

[vano6990]

Re: RPM/WOT Evinrude 115 1977

Compression test was #1 = 120 psi #2 = 110 #3 120 #4 110. Good? What next to get the RPMs up? Or will I need to do a carb rebuild?

 

[OBJ]

Re: RPM/WOT Evinrude 115 1977

I would ask again Flathead...are we sure the rpm numbers are correct? Anyway to verify that the reading true? Maybe a timing light that also reads rpm?<br /><br />How is the engine setup on the boat? Where is the anti-cav plate in relation to the keel of the boat?<br /><br />This engine have trim and tilt?

 

[vano6990]

Re: RPM/WOT Evinrude 115 1977

All I know about the Tach is I installed it correctly. It should be right because it is new and on the right setting (6p)? Will be checking timing next. How is engine set up on boat? (its blolted in lowest position. (cannot be further down). The anti cave plate is aprox even or slightly above the keel. Electric trim/tilt. Should I decarb and replace the coils & maybe the powerpack?

 

[vano6990]

Re: RPM/WOT Evinrude 115 1977

I also need to redo the Carburetors and dont know what Carburetor Kit part # I need. 1977 evinrude 115 model # 115793s

 

[ezeke]

Re: RPM/WOT Evinrude 115 1977

Carb Kit is Bombardier #439076. Aftermarket Sierra #187046.

 

[OBJ]

Re: RPM/WOT Evinrude 115 1977

Setup sounds OK. Are you triming out as the boat comes up on pad?<br /><br />And I'd go with the OEM carb kit. <br /><br />I wouldn't replace any of the ignition components unless I knew for sure they were bad. Can get expensive. Check your spark....should jump at least a 7/16" gap with a hot lighting like spark. When you run it again on the water, take a timing light with you and check each cylinder for spark at WOT. You can be dropping one cylinder at top end like Dhadley suggested earlier.<br /><br />And just some more suggestions....when you rebuild the carbs, soak them out good in carb cleaner. Blow the passages out with carb cleaner in a can and follow up with compressed air. Check the jets individually for pluggage.

 

[vano6990]

Re: RPM/WOT Evinrude 115 1977

Yes. But i do not know far out is far enough? What if I trim out too far?