Reply To: Replacing Motor

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#6454

Ahoy Bruce,

Exciting times ahead for Mystic Rose!

We strapped on a Suzuki DF90 three seasons ago and love the possibilities it opened up… when ‘opened up’. Also love that our RPM is substantially lower for hull cruising speed… and therefor so is noise and gas consumption.

I’d suggest, given the proximity to cockpit, that noise is the most significant concern for Macs… and it isn’t all just from the engine itself, but sympathetic vibrations/resonances which are amplified by our light hulls… much like the body of a violin or guitar.

I’m not too sure about the smaller-midsize engines, as all my research has been on the 90hp range. Considering the 4 strokes are all four cylinders, and 2 strokes 3 cylinders, than RPM for RPM, the two stroke will ignite combustion 50% more than the 4 stroke… therefor more noise and vibration. Also a 3 cylinder is inherantly not as balanced as a 4 cylinder. Etec has a special pontoon series softer rubber mounts available for some models which claims to reduce vibration transfer up to 30% at some RPMs.

I’d consider when was the latest technological platform of the motor released, as you ought get the best performance/economy. Etec seems to have had frequent ECU problems which are $2k to fix if not covered under warranty.

Suzuki’s are renowned for their quiet operation. The newest Mercury 75-115 claim 50% quieter at WOT than the new Yamaha.

Best ‘bang for buck’ I see is the lease return 90hp Mercs on Craigslist $6400… $6100 in Victoria. Other thing to do is just call every vendor listed on the manufacturer website to see what they have in stock/clearance and what rebates are offered from factory as it’s still boatshow promo season….

BlueWater Yachts – the largest Mac dealer was authorized by MacGregor to mount the 340lb DF70 on their transoms without modification. I had transom reinforcement bars made up for when I had my DF90 installed on our X at Brant Marine, but they didn’t use them, and stated that they mount up 250hp to transoms as thick as ours…. and thus far that’s held true… no sign of stress/fracture on our transom…. just shouldn’t be too aggressive with holeshot etc and of course pounding over/through waves for the rigging and hull/ballast tank stress. The X hull really comes to life when you get onto a true plane… and I suspect the Merc would be even better with the greater displacement torque… might even swing a larger prop… haven’t checked… have been pondering trading up to the 115hp…pitch me an offer on my DF90 if you like (500hrs, 3 year warranty remaining)

Cheers and good luck!

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