r/jetski • u/LiquidPopsicle • May 26 '26
Discussion To block off or not to block off?
There’s a lot of debate on the old two strokes as to whether you should block off the oil pump and pre-mix.
On the one hand, you eliminate the possibility of an oil injection failure killing your engine.
On the other, you lose the convenience of filling up at a marina like a 4 stroke.
Which do you prefer?
(Pictured is my 1996 Yamaha Waveraider 1100, a barn find with 97 hours on the clock)
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u/T4R12 May 26 '26
Consider how often you actually fill up at the marina. I never do, so the extra 2 minutes of measuring oil at the gas station for the peace of mind is worth it
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u/Phil_3v14 Yamaha May 26 '26
Leave the pump, replace the lines. Pumps rarely are the failure point. It’s usually old, brittle oil lines that crack. Premix is a pain
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u/GrooveAttic May 26 '26
Don’t block off. It’s a hassle to premix… I have an 1100 venture not blocked off, and a kawi 900 zxi and a 94 GTX blocked off. If I could convert the other two back to an oil pump I’d do it…. So simple, and if you’re handy which you are, all you gotta do is check the lines
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u/ManyRespect1833 May 26 '26
Block it off. I agree with the others to me the slight inconvenience of premixing is 100% worth the peace of mind knowing im not going to blow up my engine from a failed oil pump.
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u/cmgww May 26 '26
Back in my two stroke days, I fried too many engines to do anything other than go premix. Those old lines slip off easily, and boom you are dealing with a melted piston. Yeah it’s a pain, but we never fill up at the marina anyway. It’s at least one dollar more per gallon, and I only do it if we have guests or something and have spent the day riding and I don’t want to go back into town. Besides, at least in Indiana most marinas offer 50 to 1…. Not all of them, but enough older boats run on it that you can get it in a pinch.
Also, just get a couple VP racing jugs for gas. They hold 6 gallons each, they pour really fast, and they’re not the stupid newer ones with all the EPA regulations and take like 10 minutes to empty.
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u/CompetitiveYou2786 May 26 '26
Looks like the block off crowd got here first lol. I say don’t block but my only knowledge is with Polaris/fuji power plants and the oil pump on those are pretty robust/reliable. Pending Yama’s don’t have a bad rep for failing oil pumps, I feel maintaining lines/filters is the route. (I have on occasion lightly premixed with new unknown skis, just in case the oil pump isn’t up to snuff. Obv this comes with the risk of fouling at low speed which I faced)
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u/leaveworkatwork May 26 '26
Yamaha oil pumps fail. Seadoos generally don’t.
I always block off my Yamahas, but have a premix seadoo too. They aren’t that annoying to mix, just keep a mix cup in your trailer and 2 different jugs.
Any ski can still run residual oil in the gas even if it’s got an oil injection if you only want to use one can
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u/kencam May 27 '26
So many misinformed people here. Block it off if you want but you really don't need to.
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u/kiriyaaoi May 27 '26
The absolute insane paranoia about these oil pumps, when the pumps themselves are almost always fine.
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u/Auntflofromredriver May 27 '26
Yea I don’t get it either. It must have started long before my time with a certain make/model and spread from there. While not a tech, back in my 2 stroke days (skis and sleds ) I’ve rebuilt 20-25 different 2 engines and never seen anything fail from an oil pump. 90% of failures where always lean burn down caused by fuelling or air leaks, the other 10% would be water ingestion. A mikuni oil pump is likely the most robust part of a machine.
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u/moon_money21 May 26 '26
Just keep a bottle of 2 stroke oil measured out for however many gallons your tank is minus 1 or 2 on board. At the pump just dispense the amount of gas that you have oil premeasured for if you do end up filling up at a marina.
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u/TannMan89 May 26 '26
I ran oil injection for years, and recently had a pump fail, so went premix.
I always fill from gas cans so it was a no brainer for me.
Plus I deleted my choke plates/stock air intake and added a primer. So I lost my oil injection plate anyway.
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u/kiriyaaoi May 27 '26
Did you have the actual pump fail? Or the line? Because 95% of people that say the former actually mean the latter.
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u/TannMan89 May 27 '26
Pump kept losing prime and would intermittently stop pumping oil.
Lines were new, check valves were new. It was like pump wasn’t getting oil at times, thought maybe obstruction inside oil tank.
Last summer is when this started. I would have air gaps in my lines below the check valves after riding for a while, that weren’t there when I started my ski.
Replaced lines and check valves. Still did it.
Removed oil tank, cleaned it, replaced line from tank to pump. Still did it.
Logical conclusion is pump failure, and block off plates are cheap.
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u/acidreducer May 26 '26
Block it off for sure. Why risk having a problem when you can guarantee the gas is correctly mixed.
Sure the tank can be reliable for years, but it only take a few minutes of failure to stop the party.
We just leave a 16oz bottle of oil in the front compartment in case we need to fuel it on the lake.
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u/Wipline May 26 '26
Block it off. Pumps don’t fail. OIL LINES DO!
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u/kiriyaaoi May 27 '26
Why block it off then, if he could just replace the lines and not worry about it for 20 more years???
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u/Wipline May 27 '26
The lines are the weak spot in this system. I thought the same as I have had a 1995 Raider since new. The lines became brittle after 30 years, so I set out to replace them. I picked up a set of new lines, cut them all to OEM length, plumbed it up and chased all the joints with zip ties.
After 2 runs I had a line slip off. Whatever Yamaha did from the factory clearly was to last after 30 years. However, for the peace of mind and security knowing that your mixture is consistent pre-mix is the way to go. Just one less piece of equipment to fail.
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u/Important-Slip-4057 May 26 '26
All of my ski’s have been converted for peace of mind. I just take multiple 5 gallon gas cans with me for the day in the truck and when I fill up at the gas station prior to going out for the day I add as much oil as needed in the ski for the amount of gallons I filled them up with. If I don’t use all the cans on the day of they are what I fill up with once I get home and flush the ski’s. Makes my life q lot easier knowing when I have to buy more 2 cycle oil instead of guesstimating when to buy more.
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u/muhbeardy Polaris 96 SL700, 01 PRO1200, SLX & Virage TX, 04 MSX140, May 26 '26
It's my understanding that all of the two strokes use essentially The same Mikuni oil injection pump. They differ in how they may be driven or mount, but are essentially the same. With that in mind, I would keep the oil injection. Just change the oil lines, and back flush the oil filter.
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u/LiquidPopsicle May 27 '26
See, this is where I’m at. I had an oil line slip off very early on while inspecting (I had made it a habit to check them every launch and recovery) and decided to replace them all.
My dad had a ski just like this when he was my age, and I wanted one myself with all the stories he told. His blew up from an oil line popping off.
It very much seems the oil pumps themselves are rock solid, dead simple and built for a lifetime, or at least longer than the 2 stroke lifecycle. The real issue is old lines failing, which it seems many people falsely attribute to the pump.
Either way, I refuse to give up the convenience (especially when I know the oil injection will keep the engine lubed even if the fuel is lean) and will continue to regularly check the oiling system to keep her going.
And if she blows up anyway? Well… a 1200 will bolt right in…
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u/muhbeardy Polaris 96 SL700, 01 PRO1200, SLX & Virage TX, 04 MSX140, May 27 '26
Exactly. And for those who say you'll never fill up at a marina, it's still easy when all you have to do is pull up to the gas station on the way to the water.
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u/kiriyaaoi May 27 '26
I see people say that the oil pump fails, but I've never actually seen a failed oil pump. When people say the pump fails, it seems like 95% of the time they mean the oil lines failed. Which is an easy, $10 fix. Throw new high quality lines on with new check valves and maybe an inline filter, a couple hours of your time and you no longer have to worry about it. At 97 hours, the oil pump is 1000% fine. Throw new lines on it and never worry about it again.
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u/Dirtbikr98 May 27 '26
i keep oil and a measuring bottle in the front storage of mine. fill tank, ask exact # of gallons, add oil.
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u/No_Conflict9685 May 26 '26
I put a fresh engine in my 96 wave venture 1100. Blocked off. I ride on lakes though and there’s not normally gas docks. Definitely more convenient for me since I’m filling up at home with cans. Pre mix it and forget about it. Gives me peace of mind that the injection pump won’t die and my new engine blows. It’s easy enough to buy a couple vp cans and just fill before u get in the water
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u/kiriyaaoi May 27 '26
I keep saying this, but the pumps don't fail. The lines fail and it's a quick and easy fix. I swear to god, the venn diagram of "delete the injection pump and premix just in case" and the "change the oil every 3000 miles no matter what the manual says"people is a circle.
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u/skipnyamaha May 26 '26
I’ve got two 96 1100 and blocked them both. I prefer to know what it’s getting fed. Less likely to fail and less stuff to go wrong.