Evinrude 40973R 40HP Selectric Shift - Slipping or Spun Prop Diagnostics

[stevepamboukes]

Hello All,
I'm investigating a problem with my 40HP Evinrude with selectric shift. Symptoms: in forward gear, anything past maybe 1/4 throttle, and the engine will speed up but it does not increase propulsion of the boat - propulsion would remain about constant. Trying to troubleshoot/explore the symptoms, at times I would throttle up to WOT and not only would engine speed increase, but the propulsion at times would just about stop. I'd have to slow it back down to get propulsion again. This is a problem Ive had intermittently over the past year. Itd happen every now and then, so I'd just take it easy. Sometimes it wouldn't happen at all. Today was kinda the worst I've had it.

Doing some reading on the topic, I've read and agree with the following troubleshooting:
-First check selectric shift mechanism and ensure proper voltage is being delivered to lower unit. I do have right around 12.0V on my forward gear at the wiring connection near the cylinder heads. So that looks good, though that doesn't ensure I have 12.0V in he gearcase proper. Does not eliminate the possibility of a wiring fault in the lower unit. But, as far as I can see from here, voltage looks ok.

-Then check for spun prop. This is what I'm trying to verify now. The marker test makes a lot of sense: make alignment marks on hub and prop, run the boat, and see if the marks move. I just don't know when I'll put back in the water, especially given how poorly it ran today. Is there a way I can "bench test" the prob/hub interface? I removed the prob and chucked the hub fairly lightly in a vice. I wiggled the prop a bit by hand to see if it was loose. It did actually have some pretty obvious give back and forth with little torque (just applying "wrist tight" torque to the prop could get it to wiggle). It almost feels like its soft mounted, on a rubber bushing or something. Is that how these are constructed? It seems like you'd want more of a sold press fit between hub and prop.

-Then check lower unit. Hopefully I don't have to go that far. Though its actually not that bad to remove and dismantle. I suppose it could be one of those gear engagement springs? Though I remember reading the manual and the forums that, when in gear, the prop should spin freely in one direction and lock up in the other direction. I performed that test and it checked out fine. Is that a binary type test? Does that tell me pretty definitively that the springs are working properly? Do they either work or not work, or is there an in between where they can "slip" and not properly allow torque transmission...?

Let me know your thoughts...
-Steve

 

[lindy46]

I'd check for spun prop using the marker test. Must be done in the water to duplicate symptoms. You can't really "bench test". This is the most likely problem if motor revs up and goes nowhere.

 

[jimmbo]

The electric shift units make real horrible noises when they slip, kind of like a gravel crusher. Do you have another prop you can try out? You had problems last year, did it suddenly start doing this? Or was it a new-to-you unit back then?

Have you measure the resistance of the shift wires? 7 - 8 ohms to ground is normal

There is no engagement of the gears. The coiled spring while it does surround the hub it is not attached to it, it is however attached to the gear and spins with it. When the electromagnet is energized, it and the hub, which also gets some magnetism cause the coiled spring to drag against the hub and then wrap itself tight to it.
Correct oil is essential to the operation of the unit. I will assume you are using BRP Premium Blend. The unit was speced for Type C, but lately there have been oils claiming to be Type C that aren't compatible with electric shifts.

 

[stevepamboukes]

I've heard of this gravel crusher thing and I honestly can't say it was making those noises. If you're saying it would be that apparent, I probably would have heard it. I spooled up to WOT a couple times and the engine revved, and then I'd lose thrust (almost simultaneously), but it never sounded really bad. Just sounded like a loud engine not goin anywhere haha.

I have another prop but I'm not sure its in any better condition. If bench testing isn't a valid way to determine if a prop is spun or not, I'll just need to put back in with alignment marks on the hub/prop. Though I'm still curious if a little bit of wiggle in the prop/hub is normal...

The unit was new to me last year. It would do this on occasion after a 5ish mile ride, sometimes. I don't know that I've ever really been able to put full torque through this thing... sometimes the problem is more apparent than others, seemingly. Yesterday was just the worst it had ever been, barely being able to push past 1/4 throttle. without the engine "spinning out".

I can check resistance, though I recall doing that last year and it checked out. Is that back to the shift controller or down into the gearcase. If its down into the gearcase, I suppose this would test the condition of the electromagnet.

Ok to be honest I wasn't particularly careful about oil. I was just using Type C. I'll order some legit BRP premium.

Thanks for the input.

 

[stevepamboukes]

I did the resistance check and i've got 7.8 and 8.5 ohms on F and R respectively. So the coils seem good.

I've gotta get a copy of the manual for this engine in my lap again... Got one from library... im gonna re order. I'm wondering, should I have to replace those coil springs... do all those guts spill right out of the back of the gear case, or do I need to drop the LU for that operation? Would just soften the blow a bit if I could save some time...

 

[stevepamboukes]

Some questions specifically on props. I understand that there is sort of a rubber bushing in there, so it could be that the, bushing dries out and i've lost my frictional engagement between hub and prop. If thats the case, how do I identify my propeller so I can order a replacement and/or rebuild kit? Im sure I can press that bronze hub out and if I had the right kit, press it all back together.

Is it engine specific, or can I ID it using, for example, shaft OD, prop hub length, pin type, propeller quantity, etc? Or do you spec by engine type? I guess I'm just wondering how specific they are model to model or what other means can be used to ID them.

 

[flyingscott]

Take it to a prop shop they can tell you if the hub is available. A lot of those older props like that were made by michigan wheel

 

[stevepamboukes]

yea Michigan Prop has been coming up a lot. Just looking to ID the prop without having to run it all around town.

 

[flyingscott]

Look for #s on the hub usually either on the front or back of them.

 

[jimmbo]

This is for pre 64 40hp engines, but the electric gearcase stuff is identical
http://www.fiberglassics.com/library...service002.pdf

BUT, before you go ripping the unit apart, either verify the prop hub or try another prop.

Both the motor and transom are the same height? I mean you aren't trying to use a 15" engine on a 20" transom?

 

[lindy46]

Though I'm still curious if a little bit of wiggle in the prop/hub is normal...

No!

 

[Chinewalker]

Are you using Type C lower unit oil for electric shift units?

 

[stevepamboukes]

Ok, so I had some time to continue to investigate this...

I talked to H and H prop in Boston area and they helped spec a replacement prop, if I need one. Just over a hundred bucks so not bad. lindy46 , they did advise that, because of the rubber-bushed construction, a little amount of wiggle was normal. It does spring back every time, and that is the point of the rubber bushing... it would help absorb some impact if I winged something hard. They said to "bench test" those style props, they chuck em by the hub and put a breaker bar on em and test up to 600 ft-lb! I didn't have that in me

Instead of just marking the hub and prop to reference the alignment marks, I said "eff it" and just thru drilled the hub and prop, and drove in a spring pin. At least as a diagnostic, this would fix the prop in place relative to the hub, and rule out any possibility of a spun hub.

I took it out the other day, conditions were not great so it was difficult to get a good feel. Though it certainly wasn't as bad as the other day, and I was able to produce thrust closer to proportional with engine speed... so I don't think its a spun prop. I assure you the alignment marks are still lined up, and the pin is still in place

jimmbo , tell me more about that. Its been a thought of mine for a while that this could be a "geometry" type problem, where the prop just simply isn't far enough in the water. Having zero experience with small powerboats, I have no point of reference for exactly how far underwater it should be. It would seem reasonable to me that if the prop is not quite far enough under water, depending on the "geometry" (trim?) of the boat, at times I'll be pushing more froth than I am solid water, which would show symptoms consistent with "not producing more thrust, even though engine speed increases".

so can you explain where/how to measure the engine length and transom height to make that comparison? Bare with me if thats an obvious one... Other reasons I expect this could be a non-stock engine/boat configuration is that I bought it off a guy with a handful of similar sized project boats, with similar size Evinrude engines. Very possible he had been plugging and playing and just kinda messing around. So it wouldn't be a surprise if it was mismatched leg length. I have already lowered my transom once in an effort to address this suspicion.

I could take a pic later if that helps....

Chinewalker , I have been using Type C but someone suggested it was more specific... so I ordered the OEM Evinrude stuff... now I just don't want to pump that stuff in there till I replace a few seals, I think I have minor water incursion the oil comes out just a little milky sometimes and I don't wanna waste all this stuff.

 

[jimmbo]

Immediately above the propeller is the anti-ventilation plate(mistakenly called the 'anti-cavitation plate' for years). That plate at the speeds your boat motor are capable of should be level/flush with keel of the boat, or a bit lower. A picture taken level at the keel level would give an idea. No wide angel lens shots(distortion)

 

[stevepamboukes]

Ok, I finally got around to snapping a couple pictures. I haven't put a measuring tape to it yet but based on jimmbo 's description, this looks a little off. the anti-ventilation is just about flush with the keel, maybe even a bit higher. Also, looking from this perspective, the trim looks pretty far off. I've got two adjustment slots more... I can rock engine forward kicking the prop back and putting me at a much better trim angle, I think.

I've already lowered the transom once, by about 3 inches. So the engine definitely wasn't low enough in the engine's earlier configuration... and now after mods it is likely marginally positioned. Looks like getting lower would help.

I did order a LU extension on ebay for $50... its got the spacer, long shaft, and long pipes. Figured that was a good price... just a matter of doin the swap out now...

 

[jimmbo]

I'll have to lighten the shadows in PS to get a fair look at the transom height, but I can see the engine looks like it needs to be one tilt, maybe two pin hole further out.

Edit
Your engine height, assuming the boat bottom is pretty much flat across the transom looks close, maybe an inch deep. Does the keel extend all the way to the transom? If so, than the AV plate should be even or an inch below it. Some boat makers were pretty oblivious on what made a good hull

Why is a hose jammed in the opening above the AV plate?
It looks like the transom has a 3/4 inch sheet of plywood on the outside?

 

[stevepamboukes]

Good questions and comments!

Yes, I'm definitely gonna tilt the engine forward a couple pins.

The keel does go all the way to the transom. The keel itself only protrudes about 1/2"-1" or so from the hull. Right now, the plate is just about flush with the keel, if anything a bit higher. So the engine is arguably too high up.

Again, I have no reason to believe this engine was an original match to the hull. Almost certainly not: when I bought the thing, that engine was a good 3+inches higher up on the transom. I notched the transom to get it down a bit.

Yes the transom had some flex (minor) to it last year so I just glued/sealed/bolted a piece of ply to the back as a temporary measure until I get the chance to do it better. Works fine for now, water tight, no flex. Hokey, yes.

And yes, the funky snorkel. So I have a few concerns about my engine's positioning in the water. My concerns have been that, simply, its just not low enough on my transom! This is probably giving me trouble from a power transmission standpoint and, I suspect, from a coolant water intake standpoint. I find that if I get over 1/2 throttle, I really don't see the amount of water in my telltale that I'd like to see. My theory was that, again, if the engine isn't low enough in the water, then perhaps the water intake might not be low enough either... if its hanging out in the "froth zone" behind the prop (which, again, is not really far enough in the water, possibly producing more froth than it is pushing solid water). SO I made an adapter "intake manifold" that goes to some stainless flexible hosing... its basically a snorkel that will pull water from upstream of the prop, and lower in the water column.

Its funky, but testing seemed to indicate it was effective. Over 1/2 throttle, it was very definitely the most water I had seen exhausted from the telltale since I've owned the boat. Not the best metric, but the bottom line is it seems to pull water much better than without it.

 

[jimmbo]

When you say tilt the engine forward, I guess you mean from the perspective of the engine cowl in the boat?
Try running it at the height you have it currently, it might be fine. If no,t it will let you know on acceleration and on turns.
Minor flexing usually means rotten core. Fiberglass while very strong, doesn't really like flexing.

the main water intake is directly behind the prop, on the front of the exhaust snout. There is a screened inlet on the cover you removed, said for use in reverse. that inlet can and will often be out of the water when on plane. Pressure from the prop will deliver enough water to feed the pump and discharge from reverse inlet.
You engine does not have a tel-tale, unless one was jury rig added. You engine has an exhaust relief outlet that may or may not discharge water and/or steam. Your engine came with a HOT light to warn of overheating(ours came on a lot, never did find out why).

 

[stevepamboukes]

yes, from the perspective of the cowl.

I've run it at this height quite a bit.... the symptoms i've described were experienced while running in this position.

no doubt on the rotten core. This whole thing is a clunker. Its a combination of legitimate long term repairs and temporary stopgaps until I get the time/money/motivation to do it all properly.

yep, I've identified the primary water intake. the part I removed to make the intake manifold was referred to as the "water intake bypass".

well, I guess I might have used the wrong term when I said telltale. I guess I should say that, at low speeds, a good bit of water is exhausted from the exhaust relieve outlet. like if you poured out bottle of water. when I run faster, I don't get as much water. it slows to practically a trickle. that seemed unnerving. Since adding this "snorkel" even at higher speeds, I get a much steadier flow of water at higher speeds, and I see steam, which I had never seen before.

I saw the temp gauge but I tend to be skeptical of such sensors. I've never seen it go on.. which means it doesnt work... or i've never overheated.

 

[oldboat1]

(my two cents....) The shaft length looks correct to me. Need to correct the negative trim angle -- a.v. plate should be parallel to the bottom of the boat. Make adjustments from there if necessary.

Extending the shaft length would be a mistake, imo, as an extra five inches would provide too much drag with the current transom. (You need to change out driveshafts to create a long shaft, by the way.)

If you want to clean out the l.u. or run it a while to see what you have, you might use regular Dextron ATF. Fill with Premium Blend when it's ready for prime time.

Change out the impeller and the thermostat, if you haven't done that already. Description of exhaust and water flow out of the port on the leg sounds normal. The recirculation system affects the amount of water flow out the relief, and amount varies. (Working t.stat is also needed for the auto choke, btw.) Creativity points for that snorkel device -- but would interfere with cooling when operating in reverse. Would remove it, and put the plate back in place.

How about the other mechanics? Compression and spark measure out properly?