Pontoon Boat & Deck Boat Forum

Hi Guys,

I know....I know........but I did it. Anyway, 1996 Mercury 75hp 3cyl. I was running along fat and happy, when all of a sudden engine made a strange noise and when I pulled the throttle back it went dead. Started back up, and I took off, and when I reached about 2500 rpm, it did it again. Finally, it dawned on me to check the oil, since I had plenty of fuel. DRY as a bone...........so I poured oil into the oil tank, and fired it up again. Let it idle a little while while in gear limping back toward ramp. Long story short, we made it back, and just prior to reaching the ramp, I ran it on up to about 4000 rpm for a minute or so. Engine was not as smooth or quiet as it was before this happened. Loaded on the trailer and went home.

Today, I ran a cold compression check on the motor, and got 120 lbs on ALL Three Cylinders.

So..........What do you think? Is it going to survive or not? What should I do next?

Marty

If compression is good you are probably ok. I had a similar experience 6 years ago when I first got mine. Forgot to premix..... I was fine for 4 years had it rebuilt in 2012...Just keep an eye on it you should be good.

Thanks Craig,

I started the boat this afternoon on the water hose, and it sounded normal. But hard to tell anything out of the water.

On a side note......on your info you say your 24' boat runs 22mph gps! Mine is a Sylvan 24' with 1996 75hp Mercury & Aluminum prop. I checked the speed on it with full fuel 30 gallons, and me and wife. 33 mph GPS! Wonder what the difference i

Marty

blah!!!!!!!!!!!1 I think I have some water in the toons other than that no clue! I am not a speed demon though so no biggie for us..thats hauling for a 75 you sure that isn't kph???!

Or mm per hr

curtiscapk wrote:blah!!!!!!!!!!!1 I think I have some water in the toons other than that no clue! I am not a speed demon though so no biggie for us..thats hauling for a 75 you sure that isn't kph???!

Yeah, I wish my 75 would hit 33.... best I get ( and this is when it was brand new in 2010 ) was about 24, maybe 25 if the lake was smooth as glass...

curtiscapk wrote:blah!!!!!!!!!!!1 I think I have some water in the toons other than that no clue! I am not a speed demon though so no biggie for us..thats hauling for a 75 you sure that isn't kph???!

Yeah, I wish my 75 would hit 33.... best I get ( and this is when it was brand new in 2010 ) was about 24, maybe 25 if the lake was smooth as glass...

Piper5314 wrote:Thanks Craig,

I started the boat this afternoon on the water hose, and it sounded normal. But hard to tell anything out of the water.

On a side note......on your info you say your 24' boat runs 22mph gps! Mine is a Sylvan 24' with 1996 75hp Mercury & Aluminum prop. I checked the speed on it with full fuel 30 gallons, and me and wife. 33 mph GPS! Wonder what the difference i

Marty

That is insanely fast for a 75hp. Should be more like 23mph.

Ok,

Checked the app, and it was set on km. oh well, I will recheck it next time at the lake.

That's better sorry man!

Man.......your fixing to run out of gas! Better get somewhere!

Thanks for your help.

Marty

LOL

It's been out since I got the toon! Trust my eyes more than a gauge!

back on topic...

2 strokes pistons will swell with heat, especially due to a low oil ratio condition. This will make you think your engine is coming apart, and can stop it from running. Usually when it cools off, the pistons contract and everything returns to normal. I had a Kawasaki Tecate 3 wheeler with a built 250 in it, and the premix ratio was stupid critical. 41:1 would foul the plugs, 39:1 would cause piston swelling. It felt just like an engine seizure. It happened more than a few times, with no serious issues. As long as you didn't get so much heat into the rings to take the temper out of them you should be OK, and that would show up in the compression test.

Tim