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Author Topic:   170 Montauk Re-power
sloppyrudder posted 09-09-2014 07:49 PM ET (US)   Profile for sloppyrudder   Send Email to sloppyrudder  
I'm very seriously considering re-powering my 2003 Montauk 170. I currently have a Mercury 90-HP FOURSTROKE EFI. The boat originally had a two-cycle engine--that was an involuntary re-power; the two-cycle engine was stolen. Once the FOURSTROKE was put on, it changed the trim and stance of the boat significantly. She sat much lower by the stern. The Mercury is 399-lbs. I see a Suzuki is 345 -lbs and an E-TEC lighter than that. Any experience or thoughts? I know there are a bunch of threads on this. They're fairly old so I'm hoping there is new information out there.
frontier posted 09-09-2014 09:13 PM ET (US)     Profile for frontier  Send Email to frontier     
Try to find a good, used Yamaha 90 HP two-cycle. Much more low end torque than a 90 four-cycle and it only weighs 261-lbs. And higher quality than a Mercury.
Ridge Runner posted 09-09-2014 10:32 PM ET (US)     Profile for Ridge Runner  Send Email to Ridge Runner     
Are you happy with the performance of the current motor? The 170 Montauk is a pretty big 17-foot boat. I have repowered two 170 Montauks, one with an E-TEC 115 H.O. at 405-lbs, one with a Optimax Pro XS 115 at 375-lbs. Both boats have Moeller 24 gallon tanks and two Sears Marine Platinum AGM batteries in the console. I have not found any [concerns] with static trim. Both motors tilt completely out of the water. If I pull the sump plug both boats would only take on about an inch or so of water above the sump grate.

Optimax 115 170 2002%20%20Montauk%20170/P1000207.jpg.html?sort=3&o=3

E-Tec 115HO 170 Montauk%20%20E-TEC%20115HO/P1010660_zpsdcb27120.jpg

That Yamaha two-cycle engne is a good engine, but it's a pretty small displacement and known to be on the low side of its horsepower rating. The new Mercury 90-HP FOURSTOKE is 359-lbs. The E-TEC 90-HP is 320-lbs. The weight of your original Mercury Saltwater Series 90HP twocycle engine was 305-lbs. If weight is your major concern, and you want a modern outboard, the E-TEC 90HP is probably the best way to go.

jimh posted 09-10-2014 08:08 AM ET (US)     Profile for jimh  Send Email to jimh     
I am surprised that you found a great deal of prior discussion on the re-power of a 170 MONTAUK. I don't recall many discussions on this topic. The 170 MONTAUK was first introduced in c.2002, and I don't think too many have been re-powered. These days an outboard engine that is only about ten years old is not usually a re-power candidate.

It is ironic that one of the very first 170 MONTAUK boats delivered was almost immediately re-powered (covertly) with a 115-HP engine from its original 90-HP. See

The original two-cycle 90-HP sold with the Boston Whaler 170 MONTAUK in c.2002 was said to weigh 303-lbs. I am surprised that the change to the boat's present 399-lbs engine has caused such a big change in its static trim. I thought the bigger hull of the 170 MONTAUK would have tolerated the added weight without putting its stern down too much. Boston Whaler has been selling the 170 MONTAUK with a rather heavy Mercury FOURSTROKE engine for a long time. And Boston Whaler has rated the boat for a maximum transom weight of 410-lbs. However, they have continued to maintain a 90-HP maximum.

I don't think you find any modern engine suitable for the boat that weighs only 303-lbs. Perhaps the closest you can come is with the Evinrude E-TEC

Since the boat is rigged for a Mercury engine, you might consider sticking with Mercury for the re-power on the basis that it might reduce the costs by being able to re-use some of the rigging. Actually, I don't know for certain if that is going to be completely possible. Mercury has just re-done their 90-HP FOURSTROKE model (based on an entirely new engine block of 2.1-liter displacement), and I don't have any information about the details of the rigging and its backward compatibility with existing engine wiring harnesses, gauges, and accessories for this new model of 90 FOURSTROKE.

masbama posted 09-10-2014 10:18 AM ET (US)     Profile for masbama  Send Email to masbama     
Ridge Runner: Which engine do you like best? I must admit; the E-TEC looks sweet on the back of the Montauk.
sloppyrudder posted 09-10-2014 04:59 PM ET (US)     Profile for sloppyrudder  Send Email to sloppyrudder     
I'm torn, I like the E-TEC, small compact, good fuel economy. It's a 3 cylinder though, and there's no replacement for displacement. Four-cycle engines hold their value. Price is about the same. I was really hoping to get some real world experience with [unclear]. My Mercury has treated me well, it's basically a Yamaha, but, geez, it looks like the boat is being attacked by the outboard. It's mammoth!
Don SSDD posted 09-10-2014 08:15 PM ET (US)     Profile for Don SSDD    
E-TEC engines seem to hold their value really well too, according to NADA. The 2010 90 E-TEC engines are about $400 less than a Yamaha 90, and the 115 engines are $300 to $400 less. I am not sure what the difference in price was when new in 2010.

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