Gutless Glastron (1974 Johnson 85 H.P )

[EvstaG]

I seem to be having an issue with my boat which I bought at the end of last season, and at this point it is difficult to determine whether it is the boat or the motor causing the issue, so I will begin here. Here was the situation the last time on the lake:
16' fiberglass runabout, 750lb hull. Two batteries and about 8 gallons of gasolne. in stern, bilge emptied, 3 passengers totalling about 450lb

Just tuned up motor, new plugs (rest of ignition system tested okay) rebuilt carbs, decarbed, fuel pump tested moderate. Running a 14 x 17 Aluminum prop (the boat mechanic seemed to think that it was SS, however I just went and put a magnet on it to confirm my thought that it wasnt. Hmm..) Trim pin on the second hole. (I am aware the motor should be raised on the transom a notch or two, however I don't believe it should be causing the extent of the issue at hand)

Motor at operating temperature, the boat requires just slightly less than WOT to get on plane.


Also, we tried to tow one (approx 180lb) kneeboarder, and with myself in the driver's seat and my spotter in the back seat, the boat wouldn't plane out no matter what we tried, just trudged along at approximately 7-12mph at WOT, once the spotter moved to the passenger seat, the boat eventually planed out

I have had other experience with boats of similar size, and this doesn't seem to be right at all. The boat idles fine, and while I dont have a tach, it runs smooth all the way through the RPM range (hit 36mph with just myself in the boat).

The motor has been rebuilt at some point in the past, compression is good, but it just seems to lack a lot of oomph, compared to youtube videos as well as being in a similar boat with a smaller motor.

Any suggestions at this point? I apologize for the novel, and any help is appreciated.
Evan.

 

[emdsapmgr]

Re: Gutless Glastron (1974 Johnson 85 H.P )

An engine mounted too low on the transom does cause quite a bit of drag. Best to check the engine when on plane. The water flowing from under the transom should flow just under the engine's anti-ventilation plate. (that's the flat plate just above the prop.)
If it's not, you may have alot of water spray, indicating drag and poor performance. I'd think that 17 prop is about right for that boat. Probably the one that came with the engine when new... That engine is rated by the old standard, crank hp. Today's engines measure at the prop, so they effectively have about 10-13% more hp. Or the other way, is that you engine really has 10-13% less hp than today's 85 hp engines. Your engine is also smaller displacement than the 115 that year. At 92 cubic inches, it's already behind the 115's 99 cubic inches. Make no mistake, these were great engines in their time. Strong, torquey engines. I think if you fiddle with your setup you will see some performance gains for little $.

 

[GA_Boater]

Re: Gutless Glastron (1974 Johnson 85 H.P )

Has the boat performed like this since you got her? What do you mean the "fuel pump tested moderate"? It takes good fuel pressure for a motor to run correctly. Move your motor up, that can cause a big hit on performance. After that play with the trim pin settings.

You do know that neither an aluminum or SS prop are magnetic don't you?

 

[EvstaG]

Re: Gutless Glastron (1974 Johnson 85 H.P )

1. I did not know that stainless steel wouldn't be magnetic, I suppose I assumed props would consist of ferric stainless steel, and would attract the rare-earth magnet I was using at least a little bit. At any rate, the number on the propeller reads 176214, if that means anything.

2. I have taken a gander at the AV plate when on plane, and it is certainly underwater, and there is quite a bit of spray coming off the engine. That will be on the list of priorities to do, however; the bulk of the issue is before the boat planes.

3. The boat has done this since I bought it, except that now that I think about it, it seems to be a fair bit worse now, with needing to pin it to get it to plane (How much foam would be in the bilge of a Glastron runabout from the 70's? Perhaps I have to investigate for water-logging)

4. "Fuel pump tested moderate" was what I was told by the mechanic, I don't know what method/apparatus he used to test. He said it wasn't necessarily "in spec" but it was sufficient to run the motor without issues. Maybe I should be looking for a fuel pump kit. Certainly something to consider...

Finally, as I am fairly new to boating, I understand that this a pretty small boat/motor compared to what many have out there, but how much of a difference does adding weight make? Maybe the extra 80lb in the stern is what is causing the poor acceleration? For example, if I was just expecting to buzz around some kids on tubes all day, should I remove the trolling motor/ TM battery in the stern for better performance? I realize this is obviously going to be a preference thing that comes with experience, (how many times your back can handle removing the big old battery, haha) but I figure if I can gain from everyone else's experience and my own, that is extra benefit.

 

[GA_Boater]

Re: Gutless Glastron (1974 Johnson 85 H.P )

2. I have taken a gander at the AV plate when on plane, and it is certainly underwater, and there is quite a bit of spray coming off the engine. That will be on the list of priorities to do, however; the bulk of the issue is before the boat planes.

3. The boat has done this since I bought it, except that now that I think about it, it seems to be a fair bit worse now, with needing to pin it to get it to plane (How much foam would be in the bilge of a Glastron runabout from the 70's? Perhaps I have to investigate for water-logging)

4. "Fuel pump tested moderate" was what I was told by the mechanic, I don't know what method/apparatus he used to test. He said it wasn't necessarily "in spec" but it was sufficient to run the motor without issues. Maybe I should be looking for a fuel pump kit. Certainly something to consider...

2. If the lower unit is too far in the water it can certainly cause it to be hard to plane. Think about it, plane is achieved when the boat reaches planing speed. The drag from the lower and/or a mis-trimmed motor means you have to give more throttle to overcome the drag to allow it pop on plane.

3. Yes, check the foam. And pull the plug with the bow raised as far as you can on the trailer. Is water dripping out? Weight is another factor that causes slow to plane.

4. Yes, get a fuel pump kit. Let the motor develop max power. You need power to run a boat properly and efficiently.

How about some pics of the stern and motor relationship. Worth a thousand words, you know.

 

[EvstaG]

Re: Gutless Glastron (1974 Johnson 85 H.P )

2. I certainly understand what you are saying, my line of thought was simply that at a less speed the poor hydrodynamics of the AV plate should have less of an effect than at higher speeds. But what you are saying is certainly reasonable.

3. Unfortunately, there is actually nowhere to inspect the bilge on this boat. I installed an electric bilge pump (manual switch) installed in the cavity just in front of the plug, however that is the only portion of the bottom of the boat that is accessible. The water flows into the "bilge pump area" from the rest of the boat bottom through two approximately 3/4" holes, and the rest is fiberglassed up. Same story in the front under the bow, completely fiberglassed in except for a 3\4" hole, which obviously won't tell you much. The boat does leak about a gallon every hour and a half (still have to get to figuring out where all that is coming from), so every time I bring it in I tilt the trailer back all the way, and also drive home with the plug out. Perhaps a weight issue, maybe if I can get access to a scale I can see how much the unit weighs.

4. Fuel pump kit, or the whole assembly? I have the FSM and can follow instructions, so I assume a fuel pump kit would be pretty easy to install?





It is tough to see in the pictures, but the AV plate is about 1 1/4 or 1 1/2" below the pad of the boat.

And, because everyone loves videos, here is a video I just remembered my brother took on out last run out last year. I would consider that run to be noticeably faster out onto plane then the lates run this year. (In the video we were probably about -150lb in gear/people.)

 

[emdsapmgr]

Re: Gutless Glastron (1974 Johnson 85 H.P )

A really clean-looking engine. Pretty smooth running, too. Doubt you'd get that performance with a weak fuel pump. Looks to be mounted too low on the transom, from the spray coming off he lower unit of the engine. You should not see any of that V-spray that's in the video. I'll bet that it's a 5-6 mph penalty at WOT. With a stainless prop, you can even mount the engine slightly higher than normal. Such as, have the water flowing from under the transom go 3/4" inch below the anti- ventilation plate. That stainless won't loose it's bite like an aluminum prop will. Again, work on your engine setup first. (Height on transom and correct pitch prop)

 

[emckelvy]

Re: Gutless Glastron (1974 Johnson 85 H.P )

Definitely is too low on the transom. Idle speed sounds like it's way too fast.

Has anyone set up the synchronization of the linkages and checked/adjusted maximum spark advance?

Something sounds a bit dodgy with initial acceleration, maybe the primary pickup is off, hard to tell. A full Link 'n Synch is probably in order.

Another issue with these, the timer base can stick and you'll get full throttle on the carbs, but not enough timing, so it'll run doggy.

An 85hp should be able to push that hull into the low 40's at least, with some fine-tuning.

BTW what a gorgeous boat ride that was, beautiful calm water!

HTH.............ed

 

[GA_Boater]

Re: Gutless Glastron (1974 Johnson 85 H.P )

Couple of things emd. Yeah the motor is low, raise it and I think you will be surprised how much difference it makes. All the extra water that's spraying is power lost to pushing that water out of the way. Is the tilt and trim working? If it is, you shouldn't have to move the pin, just trim the boat. You couldn't ask for smoother water to test on.

On the fuel pump, a kit should have a new diaphragm and gaskets. It should be easy but I know nothing about Johnsons. Look in your FSM for the step by step instructions.

Does the boat have any round inspection hatches or a ski locker? Sometimes you gain some access under the deck through those.

Keep at it and you'll get her running like a train!

 

[EvstaG]

Re: Gutless Glastron (1974 Johnson 85 H.P )

EMD: Thanks for the suggestions, I will certainly get the setup honed in a little and report. I plan on getting a tach as well, just to add that extra element of control and adjustment.

emckelvy: This video was from the end of last year, a full link and sync was done with the tune-up this spring. It seems better now on the initial acceleration, however the issue is still that the motor doesn't seem to want to push the boat onto plane. I will try to take another video if the problem persists (thinking it may be an issue other than the motor now, but who knows). I will admit I was expecting a little more than 34-36mph when I took her out for the first time, hopefully raising the motor on the transom will help a bit!

The timing base seems to move smoothly, and goes to full advance (whatever the mechanic has it adjusted to I dont know, but it is certainly hitting the stop) I will admit, it still doesn't like to idle either. At the point when the video was taken, the idle orifices were not functioning properly, now the carbs are rebuilt and she idles on the idle orifices, however the idle advance screw still has to be completely screwed in for her to idle without eventually loading up (bogging down) and dying. But that might be an issue for another thread

To GA- unfortunately, this boat just has power tilt and not trim, so I have to play with the pin when I want to adjust that.

Nothing like ski lockers or hatches, unfortunately. I'll just have to guess and hope for the best regarding that one.

 

[emckelvy]

Re: Gutless Glastron (1974 Johnson 85 H.P )

Well, if nothing else works for the hole shot, you may want to go to a smaller diameter prop if available, it'll accelerate better.

Another thing you can do to help with the hole shot for skiing, wakeboarding, etc is to drill "ventilation holes" in the propeller hub.

One hole drilled into the hub at the leading edge of each prop blade will allow a controlled amount of exhaust gas to spill over the blades, causing a "controlled ventilation". The prop will spin up more freely under the heavy take-off load, then when you're underway the exhaust gasses are sucked out the end of the prop and pass by the holes harmlessly.

You do have to be careful when doing this, since if you get the holes too big, too much exhaust flows over the blades and they'll slip all the time.

1/4" to 5/16" is a good starting point. Some hi-performance props have 3/8" and larger holes. This works great for smaller hp motors doing watersports, and it's easy to do. If you don't like the effect, you can plug the holes back up again with rubber plugs.

Some mfr's even offer this type of prop with plugs to install when you don't want the ventilation effect.

I've attached a pic so you'll get the idea................ed

 

[EvstaG]

Re: Gutless Glastron (1974 Johnson 85 H.P )

Hmm, that is certainly something to consider for the eventual, we'll see what happens after everything else is tuned to ideal spec. Thanks for the suggestion!

 

[bailey]

Re: Gutless Glastron (1974 Johnson 85 H.P )

Hmm, that is certainly something to consider for the eventual, we'll see what happens after everything else is tuned to ideal spec. Thanks for the suggestion!

From watching and listening to your video I think that you still have a lot more in your engine either it's mounted to low on the transom our you're not getting "full" throttle I can only assume that you checked the carbs to see if they are opening completely.

 

[EvstaG]

Re: Gutless Glastron (1974 Johnson 85 H.P )

That's interesting, I was thinking the same thing too. Obviously not an accurate method being used, but simply listening to the WOT tone against other videos on youtube makes me believe that there should be "more in the engine" as you put it. Obviously the only decent way to measure this is with a tach, which should be coming soon hopefully. Yes, the carbs are both opening fully.

 

[Tim Frank]

Re: Gutless Glastron (1974 Johnson 85 H.P )

The tach should tell you whether you have the right prop or not. BTW, that # is an OMC OEM number and is a 14x17 Aluminum.

 

[bonzoscott]

Re: Gutless Glastron (1974 Johnson 85 H.P )

For what it's worth, my first boat was a 15 foot Crestliner with '70 85hp Evinrude. I tweaked that boat/motor as far as I possibly could down to waxing the hull. Weighed 1650-1700. With 3 persons in the boat, would do 32-34 MPH. One person, 38-40 MPH. Although video can be misleading, it doesn't sound like it's reaching full RPM (5500-5800). Are you sure the prop is a 17 pitch? That is what I had. For sure, look at the engine height and I'm thinking it should be a short shaft motor on that boat. You'll Get-R-Done, that motor runs good!
P.S. initially stated hull was 750 lbs, later said maybe you should weigh it. 750 + 350 = 1100. Add 700-800 for trailer - if you weigh and it is 2K or less, probably not much water logging...

 

[EvstaG]

Re: Gutless Glastron (1974 Johnson 85 H.P )

Certainly, I just have to get around to purchasing a tach (they are way too expensive from the boat shops around here). And curious, I wonder why the boat mechanic would've made an easy mistake like that. I went with his judgement (SS) simply because the prop was in such good condition, especially when compared to the skeg.

 

[EvstaG]

Re: Gutless Glastron (1974 Johnson 85 H.P )

Bonzoscott- The propeller is certainly a 14 x 17. I am not convinced of the WOT RPM either; like I said before, definitely need to invest in a tachometer. And while it may be worth it to weigh it, as said before I have no idea what is all under the deck to get waterlogged on that boat.
From your figures should basically be expecting to lose around 2-4mph/person with a boat of this size?

Thanks for the input, that certainly does give something good to relate to!

 

[Tim Frank]

Re: Gutless Glastron (1974 Johnson 85 H.P )

r. And while it may be worth it to weigh it, as said before I have no idea what is all under the deck to get waterlogged on that boat.

An inspection hatch is not a difficult or expensive retrofit.

 

[EvstaG]

Re: Gutless Glastron (1974 Johnson 85 H.P )

Yeah, that will definitely be something that gets done once I have a bit of time on my hands.