'75 Evinrude Hustler 75 HP running on two cylinders at first maybe? Need Diagnosis...

TexAgDoc

Cadet
Joined
Jun 13, 2017
Messages
10
Howdy iBoats,

First time posting on here. Wanted to revive some old hustler threads but nothing seemed to describe what I had happening. So here is the gist of it. I take my boat out on the weekends. After it has sat for a week I go to crank it up and it fires right up. No struggle, I usually give it some gas to keep her going and a touch of key auto choke. When I first crank it up like this it does not want to idle very well on its own, so with a little touch of throttle she will stay running. Then what's been happening is a minute later after I get her off the trailer I go to open it up and at WOT she can't quite get up on a plane, and it seems as though it isn't achieving full RPM. Then after about 5 min of this, there is a hiccup in the engine and the engine takes off and she runs great for the rest of the day. Also, immediately after that happens I can bring it back down to normal idle and it will idle perfectly forever.

I can't figure out the dang issue. I thought maybe I was running on 2/3 cylinders. And that maybe it was a bad coil? But to my knowledge coils don't go in and out. It's also strange because here is the series of events when I first bought it a few months ago:

1) test it in guys yard with cups on, runs great
2) a few weeks later we take it out to do a practice run on the lake, she fires right up and at WOT she runs great, no hiccups no reduced RPM. RAN GREAT.
3) two weeks later take the boat to my brother's bachelor party, right when I launch it I experience for the first time this struggle to run at a high RPM and get on a plane at WOT, after 5 min of running like this it goes like a charm.
4) the boat stayed on the water for the 3 day bachelor party and I never had a problem running it for 3 days (so always cranked up great, we left it moored every day and ran it every day, no hiccups, always ran great)
5) two weeks later take it out on the lake and this is the first time I've really paid attention to the hiccups. Sure enough after sitting for a week I go out and ask for WOT right in the beginning and she just can't do it. Doesn't sound like it is starving, just sounds like a weedeater at full throttle with the choke on.
6) This exact thing has now happened to me the last 4 times out. Everytime waiting a week in between ventures to the water.

I'm fairly mechanically inclined, but admittedly this is my first boat motor. I'm mixing 50:1 in the tank, with TCW3. No fuel filter. Also I add fuel stabilization agent (Lucas Ethanol Fuel Conditioner and Stabilizer). On my last outing I added a can of SEAFOAM (just for fun). I haven't replaced the lower unit oil, although I stuck a little wire in there and saw that it was present (this is on my immediate to do list). But this is pretty much all I've done so far.

I feel like if I had a carb problem then I would not be able to get the boat to run so great after that 5 min. In other words, I would continue to have the issue. So I'm stuck with, what gets better once being ran or heated up? Some folks I have talked to suggested a sort of vaccume issue, but seems like this would not resolve itself? Unless like there was a leak in the carb gaskets and when it heats up and expands it closes the leak?

Seems like a cylinder not firing and maybe I need a new spark plug? Or could it be that one cylinder fowls or something after sitting (sorry this makes no sense), then it takes awhile to burn it off?

I'm out of ideas here, but would like a solid strategy for at least testing on land first if possible, before I make the half hour trip to trouble shoot on water as I have limited time on the weekends and a new baby in the house (so trying to be as efficient as possible).

Sorry this was so long. Any ideas?
Thanks!
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,964
A " new to you " motor needs a new water pump impeller.---Test the spark.--Each lead must have spark that jumps a gap of 7/16" or more.----But run with a timing light to see if you can figure out which cylinder is loosing spark perhaps.--------Hopefully it is not a fuel issue as lack of fuel to one cylinder due to a plugged carburetor also means no oil to that cylinder.
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,991
Do what racer said. Also pull the spark plugs and look at them. In some ways your issue shows symptoms of a pinhole leak in the fuel pump diaphragm, or a lower carb inlet not closing and draining the fuel in the lines above it and then flooding that cylinder. Any pressure buildup in the fuel tank(OMC Portable tanks) will feed more gas
 

TexAgDoc

Cadet
Joined
Jun 13, 2017
Messages
10
Thanks guys. I most certainly appreciate it.

Racer: I believe that my impeller is working just fine right now. I've tested the temperature on the giant block (with all the bolts in it) and it remains cool to the touch. Also, when I have the boat in the water there are two tell tales that sputter water out of quarter sized holes. When I first bought it I was concerned that the impeller was shot (we tested it with cups on and no water came out tell tale) and then read somewhere that for this particular motor it needs the prop exhaust back pressure of actually being in the water to send water out the tell tale. Sure enough, when I actually ran it on the lake, this is exactly what happened. At any rate, it's completely on my to do list. Just have TexAgDoc Jr. slowing me down at home (4 months old now), so has been difficult to be efficient in preventative maintenance and diagnosis. I greatly appreciate the help.

I'm going to test the spark hopefully this weekend. It's interesting, I feel like I hear of a lot of motors running great then dying after a while do to spark issues or straight up never improving. It seems infrequent that a motor starts off slow like this then rapidly improves and will run great for the rest of the day. I'm intrigued by what Jimmbo pointed out as I've never experienced the symptoms of what a leak in the fuel pump diaphragm might be like. I guess your point about the pressure build up in the portable tank was pointing out that this could allow the cylinder to flood and take a while to clear out? Is there a way I could test this? For instance, after running for a day or even before going out, completely draining the carbs and then when I head to the lake, prime my bulb until it's taught and then remove the gas feed tube and take the gas tank and line out of the equation?

Admittedly, I'd like to do this at the lowest cost possible, and so things I can trouble shoot without having to actually replace would be AWESOME and Mrs. TexAgDoc would most certainly appreciate it as well.

Any thoughts in the meanwhile would be great. Otherwise I'll report back once I've checked these things.

Thanks guys
 
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