Mercury 150 Fourstroke - oil question

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Hey guys,

Setup:

Lund 1875 Crossover XS
Merc 150XL FS
Merc Spitfire 14x19p

We run the boat in temps between 70-90* (typically between June and Sept) in Minnesota spring/summers. Its tough for us to get out on the water consistently having small kids now. The motor sees maybe 20 hours of use a season...we do alot of a trolling with the MK Terrova.

I am debating whether or not the Merc/Quicksilver 25w40 (syn blend) or the Merc 10w30 (dino) would be "better" for our situation?

Whats interesting is Merc now recommends the 10w30 as opposed to the 25w40. After the warranty is done this year, I wouldn't be opposed to running the Rotella T6 5w40 or the Rotella 15w40.
 
I don't know a lot about the newer 4-stroke outboards, other than they are SO sweet to use.

I would think that a heavy-duty 10w30 might be better for lots of troll fishing and regular running about.

If you were pulling skiers in summertime heat, use the 25w40.

My only hope is Merc isn't going with the 10w30 just for reduced fuel consumption.
 
I ran Delo 400 15w-40 in my 4 stroke outboard for years. The Rotella would be fine.
 
What does the manual recommend? It has been a while since I have paid attention to boating but that is a pricey engine.
 
If Merc Recommends a 10w30, then that is what I would use.

My 14 year hold Yamaha 115hp Four Stroke has recommended 10w30 since new, that's all its gotten, and it runs great...
 
Manual recommends 25w40 for general use. It then goes onto say " as an optional choice we recommend 10w30 for optimum acceleration performance if you are tournament fishing or water skiing." Now why wouldn't I want "optimum acceleration performance" ALL the time!? If you check the Merc website and look at the specs for the 150 and scroll down to the Oil section it has 10w30 as the oil spec. Who knows....
 
Originally Posted By: AKA
Manual recommends 25w40 for general use. It then goes onto say " as an optional choice we recommend 10w30 for optimum acceleration performance if you are tournament fishing or water skiing." Now why wouldn't I want "optimum acceleration performance" ALL the time!? If you check the Merc website and look at the specs for the 150 and scroll down to the Oil section it has 10w30 as the oil spec. Who knows....


A reason you wouldn't need optimum acceleration performance is if the motor is pushing a barge all day. Then the 25W40 would be better.

I'd use 15W40 HDEO once it is out of warranty. 10W30 HDEO is maybe slightly preferable except for price. 10W40 motorcycle oil would work also.
 
We are going to change the oil in the next couple weeks and we are now out of 3-year engine warranty.

If you were to choose between these two oils, which would you go with:

1. Shell T6 5w40
2. Shell T5 10w30

I am leaning towards the full synthetic T6...

Again, the OM calls for 25w40 for "general use" but then 10w30 for "tournament fishing and waterskiing"...
 
Do they by that mean that short cycles of WOT and low speed over and over again is easier on oil than churning along for hours like when boating off shore?
My feeling was the opposite, but maybe Im wrong.
 
Originally Posted By: lars11
Do they by that mean that short cycles of WOT and low speed over and over again is easier on oil than churning along for hours like when boating off shore?
My feeling was the opposite, but maybe Im wrong.


I'm not sure, could go either way.

We have decided on the T5 10w30. This motor barely sees any use during the season, which is sad, but we still get out on the water which I am grateful for.
 
I have rode in a few 150 merc four strokes and I find the choice of props and gas to be very important. 2 guys used regular gas and the the motors sounded bad... also propped wrong... prop world needs to catch up to these new four stroke motors...
Last one I rode in got ETH free gas and sounded amazing... was running a 4 blade stainless...
You oil choice sounds good... I would go with RP marine myself... I also had great results with the RP 2stroke and the gear oils...
Sounds like a great boat motor combo... hope you get more use next year...
 
Yeah, the Spitfire is an aluminum 4 blade, made a huge difference in the hole shot. It just pulls like crazy when you punch the throttle. I do lose some on the top end which doesn't bother me since we didn't buy it for speed.

I have debated back and fourth about the regular 87 versus some 92/93 non oxy fuel...the motor is built for regular 87. It runs great on the 87, that's all its seen since day one. I do use Startron enzyme treatment in every tank which may help though.
 
Rode in boats this year opti 250pro xs... on 87 reg gas... did not sound right and ran a bit off.. every boat I have been in with ETH free gas way better... I wouldn't wanna give dealer chance to pull the bad gas card when you get service...
Might wanna try a few stainless 4 blades... good dealer will let you try them... I had rev 4 on my 150 opti... hole shot was amazing... like a rocket...
I used seafoam, marine stabil and merc #3 additives... rotating between the 3...
That merc 150 4stroker sounds looks like a blast to wrench on... enjoy...
 
Rode in a 18 ft triton with merc 150 thumper last weekend... 4blade stainless... complete dud out of the hole... top speed barely over 50 GPS... after 6 years with a 150 opimax on my tuffy, I would have a tough time switching to the merc 4 stroke...
 
Originally Posted By: Tuffy1760
Rode in a 18 ft triton with merc 150 thumper last weekend... 4blade stainless... complete dud out of the hole... top speed barely over 50 GPS... after 6 years with a 150 opimax on my tuffy, I would have a tough time switching to the merc 4 stroke...
I miss 2 stroke motorcycles.
 
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