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  yamaha 70 vs. merc 75?

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Author Topic:   yamaha 70 vs. merc 75?
Matthew posted 03-19-2001 11:49 PM ET (US)   Profile for Matthew   Send Email to Matthew  
Just got my hands on my Dads '82 15' sport. The fun I had in that boat on Puget Sound during my teenage years can't be measured! Looking to re-power and think that I have it narrowed to a merc 75 or a yamaha 70: the merc weighs over 300#'s and the yamaha weighs in at 228--is this a big consideration?
Both are 2 cycle and oil injected.
The merc costs $4599 including controls and the yamaha is about $800 more.
And any info the reliability of these engines or similar late model engines would be appreciated. It was originally powered by a '82 70 Johnson which really got the boat up and running.
I'm new to this forum, but have surfed around the sight the last week and found it really informative.
Thanks,
Matt
Matthew posted 03-19-2001 11:56 PM ET (US)     Profile for Matthew  Send Email to Matthew     
Disregard the weight difference between the engines--just found my answer further down in the forum
lhg posted 03-20-2001 12:46 AM ET (US)     Profile for lhg    
Also see the 15 Reference section. Jim has some good info from Clark Roberts on the 15's performance with various HP's, and some pictures of a 15 with a Merc 75 on it. Consider a 60 Merc also, 2 or 4 stroke. Yamaha 70 is nice little engine for it besides, but probably same cost as Merc 60 4 stroke. You'll probably get a better deal on a Mercury, HP for HP. Check out Bass Pro's big super store locations, east of the Mississippi only, so far, (I think). Maybe they ship. I would think 60HP 4 stroke would be the ultimate engine for the boat.
Clark Roberts posted 03-20-2001 06:19 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Matt, I agree with Larry , above! But as to comparing 70Yam with 75 merc, it's like comparing apples and oranges... the Yam is lighter and smaller in displacement.. it's about 58cubic inches (may be off on that) and the Merc is 84 cubic inches! Like a big bore V8 compared to a V6! The 75 Merc is a detuned 90hp and is a real workhorse and has thunderous torque and power... A friend of mine (see Scottfarm, Dennis Scott's posts in performance section) ... has a 75 Merc on a Montauk that runs 45mph on the GPS. I once had a 70Merc (71 cubic inch version of current 75/90) on a 15' Whaler "Mischief" that would do well over 50 mph, if you could hold it in the water! Also the Merc is technologically more advanced than the Yam. having a one piece power head with no head bolts, no exhaust baffle bolts etc and is a great engine... the Yam is a great engine also! I have owned loads of them and they are ultimately reliable and apparent quality is good. I would pick the 70 Yam for a 15 because the 75 Merc, in my opinion, would be just too much power for this old armidillo shucker to handle (the 70 Yam would be also, I think). My top choice to repower my 15 (has a 40hp 4 cyl Merc now.... and is perfect for my uses by the way)..would be the Merc 60hp 4 stroker, no question about it!!!! But, I always recommend that a person buy "what they want"! Whatever you decide to buy, hold onto your hat! Pass the waterless hand cleaner... Happy Whalin'... Clark.. Spruce Creek Navy
FISHNFF posted 03-20-2001 11:37 AM ET (US)     Profile for FISHNFF  Send Email to FISHNFF     
I too must agree with Larry and Clark. I had a 1996 Merc 75 on my 1998 Alert/Montauk and it looked big. The motor was tough and reliable, but rough. Would troll slow for hours but seemed like it would die any second, but didn't. The Merc 60 4 stroke would be a great choice. I saw one on a Montauk at my local dealer and it looked nice. Be great on a 15. Also saw an Evinrude 70 4 stroke on a new Alert 15, awesome! I talked to the shop and boat owner and it originally went out the door with a 50 Honda. Even after switching props would not break 30MPH! The boat was heavy, with custom Starboard front and rear decks for bass, trolling motor, 2 batteries, and heavier hull, and livewell. Dealer said lower gearcase was too small to properly fit the correct prop for this rig.
Back to my 75 looking big on my rig, I now have a new Merc 90 4 stroke. Huge! It does look as large as the 2.5 OptiMax, as one site on a Ventura in the next slip. The added weight on my rig actually helps. It now sits with a slight stern down attitude. With the 75, the water would not drain to the stern. A commercial friend has twin Merc 75 4 strokes on his old 21 Outrage with ribbed sides and bow deck. Dealer had to do some tricky mods to make it fit.
compounder posted 03-20-2001 12:05 PM ET (US)     Profile for compounder  Send Email to compounder     
I know that there are a lot of Merc fans on this board, but in my opinion (after having owned all the major brands) you'll be happier with the Yamaha.

I've owned 40, 60, and now 90hp Yamahas and had zero repairs, just normal maintenance. The Mercs (18hp,35hp,40hp,90hp) were all very troublesome. I can't believe its coincidental.

If you go for the Mercury, I believe the percentages are high that you will have a satifactory ownership experience. But with the Yamaha, that percentage goes up to near 100 percent.

Having a dealer nearby who is committed to customer satisfaction may be as important as the brand you choose.

Matthew posted 03-20-2001 12:09 PM ET (US)     Profile for Matthew  Send Email to Matthew     
Thanks for the info--the 4 stroke 60hp merc looks like a great option. I'll price it out today. I hope it is enough HP I'm not small, about 230, and my fishing buddies-- well no one is nicknamed Tiny!
Is there an optimal engine set up? I'll be running about 15-20 miles up and down the Puget Sound for Salmon fishing and mixing in a bit of pleasure boating/cruising with the family on Lake Washington.
Thanks,
Matt
lhg posted 03-20-2001 01:03 PM ET (US)     Profile for lhg    
Clark: Regarding Matthew's optimal set-up question, would you recommend a 5 or 6" setback transom jack for a 15, with the 60 or 70 HP is going to use?
Clark Roberts posted 03-20-2001 06:42 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
A manual jack plate of 4-6" setback should give optimum performance. I have a Bob's machine Shop MJ-5 (manual jack - 5" setback) on my 15 CC with 40 Merc and it works great. I think I would recommed the T&H manual jack plate ... 6" set-back.. it's more compact and more easily adjusted... Clark
scottfarm posted 03-28-2001 07:17 PM ET (US)     Profile for scottfarm  Send Email to scottfarm     
How fast will your alert go with the 90 merc four stroke. My local dealer has one with 2 hours on it for $5500. Guy bought it and it was to heavy for his boat. It does look huge. Dennis
FISHNFF posted 03-29-2001 12:26 AM ET (US)     Profile for FISHNFF  Send Email to FISHNFF     
Not to scare you but it is in the shop. Has a hesitation upon acceleration. I know of a few other 90's with no trouble. My 1998 17 Alert has a Montauk console with a large fiberglass box mounted on it with a high windshield, so it is very non (un?) aerodynamic. Two batteries, 10 gallons of fuel, me, and a 19" prop I touched 41 knots on the GPS. I do not know what the RPM's were due to a Yamaha motor harness talking to a Mercury wiring harness (An adapter fixed that now). The motor was on the second hole, now it is on the third. When (if) it gets out of the shop I'd love to see what she'll do. At any rate, that deal is hard to pass up. When breaking the motor in I got 7.1MPG! The way I had the extra glass layed into the hull and the fact that both batteries and the 10 galon tank are inside the console, my boat sat slightly bow down with the Merc 75 2-stroke. The 90 4-stroke gives it an ever so slight stern down so the water now drains.

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