New to me boat, ran great for about 20-30 minutes then died at idle.

mblydude

Cadet
Joined
Jul 19, 2019
Messages
10
First time boat owner, and first time posting here. This forum has helped me a great deal with my rewiring of the boat, and hope I can get some help with the motor. It is a 95 Mariner 90HP 2-stroke on a 24-foot pontoon for family and friend cruising. Engine appears to have been well maintained. Battery was dead when I went to check it out to buy it, and they spent about 20 minutes gathering the things to fire the boat up, so I figure it was an honest cold start. She fired up pretty quickly, about the 3rd try.

Got the boat home and the wiring was funky and since I had to put a new battery in it, and clean up the electrical, I went ahead and set up a dual battery system with a 1-2-B-O switch, ran new wiring, and installed it all on a Sea Sense fuse panel. Once I got that all done, all my electrical worked properly (lights, gauges, radio, livewell fill, etc.). Put the muffs on it and fired it up, and she ran smooth for about 4-5 minutes, idled it up a bit during that time too, and it all sounded great. :dance:

Felt like it was ready to hit the water, but didn't want the maiden voyage to be with the family, so I had a chance to work out the kinks and make my wife's first trip on it an enjoyable and stress-free one so she stays on board with it all. :wink:
So a buddy and I took it out, and nailed the launch. Took us about 5 minutes from the time we started backing the trailer down to pulling the truck up to park it. I idled the boat around the dock waiting for my buddy for about 5 minutes, got him and we are on our way. Cruised for about 8-10 minutes at about 1/4 throttle, just getting a feel for it. Gave it some more for a few minutes, slowed down a bit, made some wide turns etc. just feeling the boat out. I was ready to open it up and we went WOT for about a minute or two, just so I could get a feel for that too. In total we were out about 20-30 minutes, and as soon as we pulled up to a cove to park and hang out, the moment I throttled it back down, it started to sputter and died a few seconds later. :grumpy:

We were in a cove so I dropped anchor and we let it sit for about 30-45 minutes and tried to start it again, same thing. Motor turns, but would not catch and fire up. Occasionally it would give like one or two heavy chugs like it was going to, but just didnt. Primer bulb got hard when we primed it. Tried starting with choke, with some more idle, while priming...nothing got it to catch. Took the cowl off to look for any pinched or kinked hoses. Plugs all look good and snapped in tight. Checked linkages with throttle and they all appear to be working. I could see there was oil in the oil feed line to the pump, but the line coming out of the pump was not FULL with oil. (picture a horseshoe, with oil at the two ends, but none in the middle). I know we were running with oil because there was slightly less oil in the reservoir than when we started the day. But as soon as I dropped the throttle down for no wake, it sputtered and died.

Any ideas what I might try looking into?:help:
 

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Last edited:

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,033
Did you replace water pump impeller ?-----Did you verify that oil pump is turning?-----I would now do a compression test first.
 

mblydude

Cadet
Joined
Jul 19, 2019
Messages
10
Did you replace water pump impeller ?-----Did you verify that oil pump is turning?-----I would now do a compression test first.

Water coming out the impeller the whole time. There was less oil in the reservoir when we stopped than when we started. Is there a way for me to check if the oil pump is turning at this point, like something I can do with the boat sitting here at my house?
I will try to get the compression tester today and see what the numbers look like.
 

mblydude

Cadet
Joined
Jul 19, 2019
Messages
10
Did you replace water pump impeller ?-----Did you verify that oil pump is turning?-----I would now do a compression test first.
As mentioned before, impeller is functioning with a steady stream that comes out. When I try to crank the motor for a few seconds, it started coming out right away.

Tried compression test, but since the motor would not start, I could not get it to warm up first. I know doing it cold is not really what I need to do, but figured it would at least be some piece of information. All three ports read right around 105-108. What I did notice though is that when I left the gauge attached, the pressure did steadily drop on all three, all at about the same rate. My thinking (hoping) is that that is just a matter of either not getting the compression fitting in tight enough (though I hand tightened till it wouldn't turn in anymore), or it being a result of a cold motor, where the internal parts haven't had a chance to run and get all the parts to heat and swell to normal operating conditions.

As for the oil pump, I am not sure how to check to see if it is turning. I am willing to read and watch videos and learn, so if anyone has a good way to point me, I'm persistent enough to figure this thing out.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,033
If the gauge drops pressure your gauge has a problem !----Nothing to do with the motor itself !
 

mblydude

Cadet
Joined
Jul 19, 2019
Messages
10
If the gauge drops pressure your gauge has a problem !----Nothing to do with the motor itself !

So then the readings that I got on it are ok, or are you saying that the readings that I got on it are worthless?
 

mblydude

Cadet
Joined
Jul 19, 2019
Messages
10
Checked plugs with inline tester. I got a light on all three cylinders but still no start.
 

mblydude

Cadet
Joined
Jul 19, 2019
Messages
10
First compression tester was a dud, didn't feel like the hose really connected tight into the gauge and I didnt want to trust the numbers. Took it back, got a different one (actually held the number on the gauge). All three were 118 or 119 (just a shade under 120).

Here's where I am so far. Started up day 1. Ran fine including idle at first. Ran for 20-30 minutes at various speeds. As soon as throttled back to enter no-wake zone it sputtered and died. Would not fire back up.
1-Single warning beep when I turn the key (monitor system is working).
2-Linkages are good. (throttle and reverse throttle all move freely and are attached as they should.
3-Primer bulb gets hard and is sending fuel to carbs (opened bleed screw and pumped bulb a few times to verify that.)
4-All three spark plugs tested good with an inline tester (the light came on but still didnt start the motor, so I think ignition system is all good.)
5-Compression checks right at 118or 119 on all three cylinders.
6-when I bought the boat it had less than a quarter tank of gas in it. Not wanting to trust that entirely, I filled up with ethanol free gas. I guess it could be bad gas, but I went to this spot in particular because many people have told me they had the right stuff for boats.

My gut is telling me the oil pump assembly is my next check? To get to that I have to take off the air cover and the carbs. I figured at that point it wouldn't hurt to clean the carbs? (since they will be off anyways and no motor is ever hurt by a carb cleaning)

Does this sound like i'm on the right track here, or am I missing something obvious? (and much easier/cheaper)
 

mblydude

Cadet
Joined
Jul 19, 2019
Messages
10
Got a can of 50:1 pre-mix and a spray bottle. Helper turned the key while I sprayed into the air cover. Still no catching and firing.
 

mblydude

Cadet
Joined
Jul 19, 2019
Messages
10
racerone (or anyone else who has an idea), how do I check if the oil pump is turning if I can not get the engine to start? You asked about that before. I know if the engine is running off of a 50:1 premix in the tank I can do some things there, but I can not find anything about how to check this if the motor will not start.
 

mblydude

Cadet
Joined
Jul 19, 2019
Messages
10
I have read elsewhere about a plastic gearing inside these pumps that has been known to fail? That gearing will break and then the pump would cease to be operational. At least I think that is how I understand it.
 

mblydude

Cadet
Joined
Jul 19, 2019
Messages
10
Used an open gap tester for the coil and the spark was firing well over the recommended 7/16". Tried it close to a full inch and there was blue spark across the gap.
Tried new spark plugs, still not starting.

Running out of ideas. Anyone on here have any other ideas?
 

dadofemily

Cadet
Joined
Mar 25, 2019
Messages
18
Can you see the throttle plate opening in the carb. Possibly your linkage has malfunctioned and the carb is staying closed. This would explain it popping slightly but never running.
 

pascoea

Seaman Apprentice
Joined
May 8, 2017
Messages
44
I was a little unclear when you said you were spraying fuel into the air cover. Are you saying you were spraying it directly into the carbs? (I'm not familiar with this specific motor, so this could be a dumb question.) If you weren't, I would try that.

If that still doesn't work, take the plugs out and see if they are wet.
 
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