WOT RPMs 77 Evinrude 85 hp

[jmcgill89]

Last weekend was the first time I took my boat/motor out for a weekend's cruising with a working tachometer. Prior to the weekend, I performed a de-carb just to make sure everything was running well.<br /><br />My boat is a 1978 Glastron 17' with a "semi-v" hull. I just bought this boat and motor, so what I am reporting is the setup it came with. When I was out, I got a consistent 4500 RPMs at WOT. This worried me initially because of all the 5800-6000 RPM talk I hear from people on this site in reference to V-4 motors. However, when I looked at my Evinrude instruction manual, it says that the range for WOT RPMs is 4500-5000.<br /><br />I've not done a compression test yet to answer that question.<br /><br />Are these RPMS ok, or should I be worried?<br /><br />Thanks,<br /><br />Joe

 

[Dhadley]

Re: WOT RPMs 77 Evinrude 85 hp

First we need to verify the tach and motor. Is the motor healthy? Is it an E/J tach set on position 6?<br /><br />If the motor is running on all 4 and the tach is correct the r's need to come up for efficiency and longevity. 4500 is putting quite a strain on it. <br /><br />We'd like to see your motor at least in the 5600 range, but closer to 5800.<br /><br />Good luck!

 

[ob]

Re: WOT RPMs 77 Evinrude 85 hp

Joe ,Also try posting the diameter and pitch of the prop you are currently using to drive this rig.Prop pitch is critical on each different setup as it pertains to wot rpm capability.

 

[jmcgill89]

Re: WOT RPMs 77 Evinrude 85 hp

I know the pitch is 15, but I'll try to look for the diameter, etc.<br /><br />I know that all 4 cylinders are firing, how well, I can't say. The tachometer is not a Johnson/evinrude tachometer, and I don't know how to check where its set.<br /><br />I know the first step in these situations is to check the compression, but I'm poor and don't have a gauge....I'll try to get one. I just changed the plugs and they looked great after my first week's use with the new plugs. <br /><br />Is there a way to adjust the throttle linkage, etc. to bring up RPMS? I have the feeling that the carb/throttle should be adjusted.<br /><br />The motor has never been taken apart....the paint is not cracked around the head gaskets.

 

[Dhadley]

Re: WOT RPMs 77 Evinrude 85 hp

If the tach is not a factory one we need to verify its readings. Any mechanic should have a shop tach. Its a portable tach that clips on a plug wire.<br /><br />Yes, compression is always the first step. <br /><br />And yes, if the spark and throttle linkage is not advancing properly to wide open you can get reduced performance. When you push the throttle wide open the timer base should be aginst the rubber on the stop screw and the carb throttle plates flat. With the motor off have someone gently turn the prop while you shift it into gear and push the throttle to wide open. Take the key out of the ignition for this.<br /><br />A 15" prop should be about right on that boat with a healthy motor. Perhaps even a 17". Thats why we need to verify that the motor runs on all 4 as it should and the tach is correct.

 

[jmcgill89]

Re: WOT RPMs 77 Evinrude 85 hp

I'll check the spark and throttle linkage when I get home today to see if it's correct. I asked that question because it seemed that these were "loose" when I was first looking at the motor.<br /><br />How can I verify if it is running well on all 4 cylinders? Could I have one (or more) coils going bad?<br /><br />I have a shop tach that I use on my Volkswagen, would it work on my outboard? It's one with 2 clips...one that grounds and one that goes on the ignition coil....I'm not sure how that tach would work when running the motor with muffs anyway.<br /><br />Joe

 

[Dhadley]

Re: WOT RPMs 77 Evinrude 85 hp

You need a 2 stroke outboard shop tach.<br /><br />Yes, one coil can be weak or bad.

 

[jmcgill89]

Re: WOT RPMs 77 Evinrude 85 hp

Also,<br /><br />Where could I get an OMC or equivalent tachometer to put in my boat? I don't trust that one I have there now.<br /><br />How do I test if a coil is going bad?

 

[Dhadley]

Re: WOT RPMs 77 Evinrude 85 hp

I would suggest sticking with a factory brand tach for the most accurate. Any J/e dealer stocks them or try www.surplusunlimited.com.

 

[jmcgill89]

Re: WOT RPMs 77 Evinrude 85 hp

I checked out the throttle linkage last night. I believe the area Dhadley was talking about is right under the flywheel. If that's correct, the rubber stop was toughing the plate. So I guess it's not the linkage. <br /><br />I bought a compression gauge, and now I have to figure out how to use it. How do I disable the ignition while still being able to crank the motor to test the compression?<br /><br />Thanks,<br /><br />Joe

 

[Solittle]

Re: WOT RPMs 77 Evinrude 85 hp

Joe - You mentioned checking the instruction manual. Is that the owners manual or shop manual?? If the owners manual you need to get the shop manual. I got mine here:<br /><br /> http://www.theoutboardwizard.bizhosting.com/parts_service_and_owners_manuals.html <br /><br />Follow the troubleshooting procedures & don't try to shotgun with guess work.