Very Slow 7.5 Evinrude

Miss Lana in VA · Aug 13, 2001

Re: Very Slow 7.5 Evinrude

RWISE, you may have a point on the linkage, I dunno...I will check. A say this because, even though the handle moves the complete 180 degrees in all modes, I will take a close look at the small linkage at the carb this weekend. However, I do not fully understand it. I believe all of the throttle linkage works the same, regardless of which gear it is in. Thanks to all that are adding to my education. It is nice to have a few good guys around.

fone_man · Aug 13, 2001

Re: Very Slow 7.5 Evinrude

Miss Lana: JB will get you fixed... I have faith in him plus he is all rested up from his vacation & he needs a tester to get his feet wet again... Take that laptop with you to the boat & we will all will be watching the board as repairs/testing is in progress!!! Good luck... if it doesn't have a hole in it, it can be repaired/fixed!!!

------------------ "Keep It Between The Bouys" & "Good Luck"!!! fone_man

Miss Lana in VA · Aug 14, 2001

Re: Very Slow 7.5 Evinrude

After reading other simular questions on this board. I started thinking again. Well, I need your input on reed valve direction. I failed to say earlier that when I was cleaning out the Carb, that the reed valve had a piece of dirt stuck in the opening. Once cleaned, one of the reeds had a slight bend in it which caused an OPEN state. So to remedy this I simply turned the reed valve over and re-installed in into place. ????? Question - Is the reed valve unidirection upon install?

JB · Aug 14, 2001

Re: Very Slow 7.5 Evinrude

Guys who sell reeds and some others say don't do that, Lana. I did it for years and suffered no ill effects. I believe you are safe. Looking foreward to new developments. Red sky at night. . . JB

Miss Lana in VA · Aug 19, 2001

Re: Very Slow 7.5 Evinrude

Here are the results to the Compression Test. Top Cylinder shows 75 psi Lower Cylinder shows 55 psi First, let me start by saying I wish I knew the correct technical names and descriptions. I will try my best to describe below my processes. I have ordered a shop manual for this engine range, should come in next week. I am more than a little embarrassed, scared and uneasy about this ordeal and ask for your consideration and empathy. I have removed the Air Filter two week ago. I have an unobstructed air flow to the carburetor. This is the process I followed last night: I motored out about 10:30 pm (20 minutes) – RPM’s at about half speed – Strong flow of water from the discharge tube. I then sailed around for 2 hours. Then I Motored back into port – (15 minutes). While coming in, the engine shroud/cover felt hot to the touch. So, I took of the shroud while still motoring in. After about 30 seconds (with Shroud OFF) I started getting higher RPM's and more speed, this was great. I was actually cruising at near full RPM’s at WOT. Still getting a strong flow of water from the discharge tube. I ran this way for the last 1000 yards into the slip. I shut down the engine and after securing the rigging and the dock lines – (15 minute) I proceeded to remove the Top sparkplug. The engine was still very Hot. I could not hold the plug in my hand with out using a wet shop towel. I installed the Compression tester (Hand tight) into the top cylinder and started the Engine. Results showed 75 psi with engine running. Then I replaced the Top spark plug and spark plug wire then removed the lower plug to test the lower cylinder. I installed the Compression tester (Hand tight) into the LOWER cylinder, but was unable to start the engine by the pull String. So, I used my electric Drill with shore power to spin the flywheel very fast. The engine still did not start, the Compress gauge showed 50-55 psi during this test. I then put everything back together and started the engine. This is when I noticed a steady ARC – a spark hitting the top dorsal portion of the engine. It was ONE HALF inch below the top throttle linkage. From a small brass connection on a thin wire coming out of what looked like a power pack (the size of a Cigarette box). I shut off the engine. The arc extended about 1/8 inch. Was this making the engine so hot? I am lucky I did not have fuel fumes in the housing, it was certainly would have caught fire. My assumptions: - Motor is running on bottom cylinder only. - Motor is a fire hazard - I have two good fuel pumps. (newest installed) What is my next step?

JB · Aug 19, 2001

Re: Very Slow 7.5 Evinrude

Hi, Lana. You are a pretty darned good trouble shooter. . . very observant. It is as I suspected in my last post: down one cylinder. The arcing you found is almost certainly the energy intended for the top plug. Trace the offending wire. If it has terminals at both ends, replace it with fresh wire that has good insulation on it. Dress (place) the wire so that it doesn't contact any grounded surfaces. If you can't replace it, wrap it with rubber (not plastic) electrician's tape. Be sure that you examine the inside of your bonnet to see that it cannot arc to that or be pressed down by contact with it. Now try her again. Okay? Bon Voyage!! Not okay? proceed. I don't have a 7.5 manual so I have to do a little guessing, here. If there are two coils, swap them and see if the top cylinder takes over the load (a bad primary winding on a coil may cause the arcing you found). Let us know what happened, be sure to monitor your engine temp. It probably got hot from one cylinder having to do all the work. Once she is running right again, we need to address compression again. Red sky at night. . . JB

Miss Lana in VA · Aug 19, 2001

Re: Very Slow 7.5 Evinrude

OK...

Feeling better now. I will continue with your recommended activity and report the results. I will look at this from now on as FUN

JB · Aug 19, 2001

Re: Very Slow 7.5 Evinrude

Good. There are few things as satisfying to a heuristicist (problem solver) as whipping a tough one. You are getting there! Red sky at night. . . JB

Chinewalker · Aug 20, 2001

Re: Very Slow 7.5 Evinrude

Miss Lana, Was just following your thread here. One thing still bothers me about your tests. You had a 20 psi difference between the two cylinders which tells me something is up with your compression. I don't generally like to see more than a 5% difference between cylinders. It might be as simple as carboned rings, but you also mentioned the motor felt VERY hot. I suspect you may have other issues at work here. It may have gotten hot enough to melt one or more of the ignition components, creating the arcing you noticed. I would proceed with caution and be careful about sinking a lot of money into it before addressing the compression issue. You sound quite handy, so a re-ringing may not be out of the question and would certainly be a lot cheaper than a new motor. Be careful! - Scott

JB · Aug 20, 2001

Re: Very Slow 7.5 Evinrude

Hi, Scott. I noted both the temp issue and the compression issue. Running at WOT with only one cylinder firing is guaranteed to get it hot. The compression numbers were taken under different conditions, therefore the difference is useless. As you will note, I addressed both issues in my last post. Please don't distract her from the immediate problem: get #1 firing. Thanks for your interest, and stay with us, we may need your help. Red sky at night. . . JB

Miss Lana in VA · Aug 26, 2001

Re: Very Slow 7.5 Evinrude

Note: I am getting Spark in both cylinders. Maybe Thursday or Friday I will take and place photos of this engine and close-ups on the web for your visual inspection. I traced the wire that was arcing. It did not have terminals at both ends. The wire doesn't make contact with any grounded surfaces. I secured and wrapped it (at the top Connection) with rubber electrician's tape. There is only one coil,(did I miss something?) so I had nothing to swap. I am still getting spark in both cylinders No change in performance.

JB · Aug 26, 2001

Re: Very Slow 7.5 Evinrude

AARGH!! I wrote about 300 words, then asked to review the topic and lost it all. Hi, Lana. I was hoping for better news. Let's go to the two open issues: compression and temperature, and add a piece of data I don't think you have posted: what year is your 7.5? Please run a new compression test with the plugs out, and cold. Your previous numbers were bad, but taken under invalid conditions. Your description of the engine temperature, while subjective, suggests it might be getting too hot, in spite of a strong telltale stream. Standing by for year and compression figures. Big Four (Scott), please jump in here if you have any ideas. Red sky at night. . . JB

Miss Lana in VA · Aug 26, 2001

Re: Very Slow 7.5 Evinrude

I was told by the wrench at the marine shop that my Evinrude 7.5 was a 1972 model. I will verify this on the Certificate of Title and let you know. Thanks for all of you help. It has been fun....

I would like to resolve these issues soon. On a side note : My three girlfriends and I have chartered a Swan - 40 footer for a sail to Hilton Head. ( I turn the BIG 40 on Saturday)

We leave at first light, wish us luck. We will be on SAT and I am bringing the Laptop with me.

Hi&Dri · Aug 26, 2001

Re: Very Slow 7.5 Evinrude

J.B., Going back to a previous post... removing the cowl brought the revs up... If there were mud daubers in the carb, why not in the cowl air intake, too? Mike

JB · Aug 27, 2001

Re: Very Slow 7.5 Evinrude

That makes sense, Mike. There are other questions about why it picked up with the bonnet off, as well. I am also wondering if muddaubers could be responsible for the heating. Lana, congratulations on getting later in youth. All of the women in my life. . . Mom, 2 sisters, 3 daughters and a former wife, reached the peak of their powers well past 40. Have a ball. Red sky at night. . . JB

Chinewalker · Aug 27, 2001

Re: Very Slow 7.5 Evinrude

Something isn't working out here. First, I think your mech is mistaken on the year, as OMC didn't build a 7.5 in 1972. They made 7.5hp motors from 1955 to 1958 and 1981 to 1983. I suspect your motor is the latter version. Second, fixing the ignition problems isn't going to fix the root problem - the motor has overheated at some point and cooked one or more ignition parts and also caused the motor's low compression numbers. 50 or 70, hot or cold, it doesn't matter - they're way off of the 90+ they should be. If taping things up is enough of a fix to get it firing on two cylinders, Lana's initial complaint that the motor had no power will remain. I'd hate to see her invest a couple hundred bucks in ignition parts and have it still be gutless when trying to get into here slip back at the marina. I guess my fear is that this motor may be toast, unless you can find a parts motor with decent compression to mix and match with, or if you've some time and a good manual, you can rebuild it yourself. At around 20 years old it's not really worth it to have a motor that small rebuilt at a shop. - Scott

Miss Lana in VA · Sep 2, 2001

Re: Very Slow 7.5 Evinrude

Well, I am back... The Engine is a 1982 Evenrude 7.5 It seems I will need to fix the Compression issue somehow. When I took off the Head sometime ago, I did notice that I could move the pistons little from side to side when they were on TDC. I thought this was normal for an engine of this age. The tops of the pistons look very good, no cracks or holes. However, reading the results from the tests listed on this board, I believe that the rings are not allowing adequate compression in the top cylinder. Are my assumptions correct? Will I need larger Piston and Rings? Or just larger Rings? Is this something I could do???? Or should I allow the local High school “Shop Class” does it for me?

JasonJ · Sep 2, 2001

Re: Very Slow 7.5 Evinrude

Just a comment: If you just put the head back on without a fresh head gasket and the bolts not torqued properly, you could be losing compression because of that. If this is the case, your compression readings won't be accurate. Also, have you tried new spark plugs? Sometimes plugs just go bad. Also, if it is running better without the cowl, could there be an exhaust leak that the carb could be drawing exhaust in, causing a drop in power?

Miss Lana in VA · Sep 2, 2001

Re: Very Slow 7.5 Evinrude

Using New Plugs - gap 30 Using New head gasket How do I test for Exhaust leak?

JB · Sep 6, 2001

Re: Very Slow 7.5 Evinrude

Ahoy, Lana. Now I, too, am back. Scott's post from last week (Chinewalker) is probably a bull's eye. There are a few things you can do to prove his postulations, but he is almost certainly correct enough that your engine needs a major overhaul and parts of your ignition system replaced. You can still do a valid compression test, but both cylinders would need to come up to over 90# and within 10 or 15# of each other to indicate a healthy mechanical system. You can still do a part-by-part dynamic test of your ignition system. I think it is usable as is, but Scott's prediction that parts have been roasted may be true. You can rod out your cooling passages in search of a cause for your heating problem. I think that the better running with the bonnet off is temperature related, but it could have to do with leaking exhaust gasses starving the engine for oxygen. I think you would hear an exhaust leak. Bottom line? Replace the engine, or at least replace or rebuild the powerhead.

Be sure you have a prop suitable for pushing a sailing vessel with the gear ratio in the foot. A fishing boat prop has too much pitch for your application and will overload the powerhead, causing the kind of problems you now have. You seem a competent user of tools. I think with a manual and good local machine shop assistance (boring your block) you could do it yourself. You need to decide if it (and the intangible benefit) is worth the expense. Red sky at night. . . JB

Very Slow 7.5 Evinrude

Seaman Apprentice

Senior Chief Petty Officer

Seaman Apprentice

Honorary Moderator Emeritus

Seaman Apprentice

Honorary Moderator Emeritus

Seaman Apprentice

Honorary Moderator Emeritus

Fleet Admiral

Honorary Moderator Emeritus

Seaman Apprentice

Honorary Moderator Emeritus

Seaman Apprentice

Cadet

Honorary Moderator Emeritus

Fleet Admiral

Seaman Apprentice

Rear Admiral

Seaman Apprentice

Honorary Moderator Emeritus