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76 Glassmaster 15 ft. tri, 1976 Evinrude 75 Hustler bogging down

Randy Pace

New member
Hello all. I've read thru the threads I could find here on this, and can't seem to come to any conclusions.I bought the boat from my father in law. He had a few things done to it. Carbs flushed and rebuilt, new fuel pump, powerhead(?), and a few more smaller things. Motor runs excellent out of the water on a waterwing. Good exhaust, good water flow for cooling. But get it in the water, and it bogs down. I know car and truck motors, but not boats. Once in a while at almost WOT, it ALMOST wants to "break loose" and really haul, but it's only for a split second. I flushed the tank and fuel system, so it's all working as it should. Where to start? Thanks for any and all input.
 
I have come to the conclusion that if you are going to work on your own engines, then three things are necessary.
Factory manual. No substitute. You can buy them on this site if ebay is out.
Compression tester, and spark tester. I bought mine at a local auto parts store.

One check compression and spark.
Two likely you will need to go through the carbs yourself the right way.
Take pictures before disassembly. When I did my 73' it was a full two weeks before I got the carbs back on. Yes they were that bad. I do have a 76' as well, just not the hustler. They are a joy to work on, but be patient.

Some more history on the engine would be helpful, like how long was it sitting, etc.
I don't know why you didn't get any responses, usually the guys here are really great.
 
Thank you for the reply jim. I see a lot of replies to most everything else here, which was why I decided to post for some ideas.Compression and spark are great on all 3 cylinders. Engine sat for a season with fuel in the lines, which is why I drained and flushed the fuel system. Right now it has Champion spark plugs in it gapped at 32. I will be changing them to NGK Marines shortly. Last summer, the in law took me out on it, and it just flat out hauled a@@. I'm thinking possibly the inners of the carbs are gummed up with last years fuel that he didnt drain out. I have a spark and compression tester. The manual I am waiting for. Again, thank you for your reply.
 
It is most likely with this engine that the oil of the gas mix settles down in the carbs, you should also check if the
valve opens correctly. When one cylinder wouldnt get gas this engines die.
I have a 1978 75 hp evinrude and when i first bought it the carbs where full of old greasy oil , and it also just started when pumping a lot of gas which floated and made it run a little.
 
Over a week, and no replies. Thanks folks. Can't believe all the boat motor mechanics on this forum have no opinion on this.

Oh hell Randy, you know we never did like you ;). Seriously, I don't know how I missed this one. Now, before anything, do the basic trouble shooting procedure. Remove the spark plugs.

The s/plugs should be Champion QL77JC4 plugs gapped at either .040 or .030 (original and revised recommended gaps).

Do the plugs all look alike, what do they look like? Are there traces of water on any of them?

Check the compression. What are the psi readings of all cylinders?

With the s/plugs still removed, rig a spark tester whereas you can set a spark gap of 7/16". The spark should jump that gap with a wide strong blue lightning like flame... a real SNAP! Does it. Note that the gap is important!

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:
 
..........X1..........X2
.................X..(grd)
..........X3..........X4

Bogs down.... when? When throttle is applied, going to full throttle? What? Describe the problem exactly. As it stands, your explanation could mean the engine is bogging when throttle is applied, or missing on a cylinder constantly but cutting in occassionally, sort of a up in the air thing.

If the compression and spark is as it should be, the usual cause is clogged high speed jet(s), a sticking timer base, or the carburetor throttle butterflies are opening too soon.

Let us know what you find.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:
http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
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Spark and compression are good. Pulled the carbs, and shot 'em full of Gunk Carb Cleaner, let them sit for an hour, then did it again. Just got the ball and trailer lights hooked up to my Blazer, and gonna try it out on Wednesday. Number 3 carb (lowest down the line) was gunked up from sitting and not being bled down for the winter, just full of green stuff. Number 2 was okay, but all of them had the green crud in 'em. Here's hoping. And I thank joereeves for the reply, cuz I don't much like y'all either. LMAO. Y'all have a great night, and I'll let you know on Wednesday how it goes.
 
If that engine still bogs down, double check the brass high speed jets that are located in a horizontal position in the bottom center portion of the float chamber. Clean them with a piece of single strand steel wire as cleaning solvent doesn't do a proper job on those items.
 
You've stated a couple times that "Spark and compression are good".... That doesn't tell us what PSI you're obtaining on each cylinder OR if the spark is actually jumping the required 7/16" gap with a strong blue lightning like flame, a real SNAP!

Frankly I advise against the NKG plugs and highly recommend the Champion QL77JC4 plugs gapped at .040. You can try the .030 gap setting later if you like to compare changes in performance if any.
 
Spark is jumping the 7/16" required. Nice pretty blue one too! :). lol I kept the Champions in it, and they are at 35 or so. I will down them to .30, then play with it to see what works best for it. Compression sounds good, as it cranks with the first bump, not even a full revolution. I have to get it to my mechanic who has the compression tester. Any other ideas for me to try out?
 
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