Engine Upgrade 650 to 701

This Whaler is fortunate to have an engine model that has easy upgrade options. I decided to go with a 61x case and cylinder that will bump my engine HP output from 50HP to 63HP. It also allows me to start with a freshly rebuilt engine that I'll install with an Hour meter.

Yamaha built these engines from 1991 thru 1996 I believe. From what I have read the Yamaha 650 and 701 are as follows.

6m6: machine name of the 650 (single 44 mm SBN carb, 77mm bore) - 50HP Stock

61X: machine name of the first yami 701 (single 44 mm SBN carb, 81mm bore) - 63HP Stock

62T: machine name of second yami 701 (twin 38 mm SBN carbs, 81 mm bore) - 73HP

This is my stock 650 engine out of the Whaler sitting on a cooler.

I was able to identify my engine cylinder type by markings underneath the intake ports.

You can either buy a rebuilt 701 (61x) engine outright for around $1000 or find somewhere to get yourself a cheap core. You might scrounge one for around $300. At this time building one from scraps on Ebay would cost even more because a set of rebuildable jugs (cylinders) was over $100 I got lucky and found a decent whole core for $300 that included shipping. I had the seller send it directly to SBT for an exchange to save on the nearly $80 shipping.

More to follow!!!

12/11/12

SBT called me to confirm that my 61x core arrived and that they will "bank" it for me when I want to order my 701 engine.

12/17/12

Ordered the 61x engine from SBT today. Totaled $609 with shipping and the gasket kit. $600 for a totally rebuilt engine to your door isn't something you can really argue with.

12/19/2012

Wow...The rebuilt engine showed up here from Florida in 2 whole days. I'd like to go wild and start installing it tonight. Kind of sick of the mess in my garage, but I'll save it for one of my days off after Christmas next week. The engine came with an owners manual that had several useful links besides installation/removal such as pump blueprinting guides, carb tuning and rebuilding. All these can be accessed at SBT's home site.

The intakes and exhaust look similar between the 650 and 701 model. The intake manifold and reed cage wont even fit. The exhaust manifold will actually bolt on the 701 but will hamper power output due to smaller exhaust diameter than the ports. I've heard you can align a 701 gasket up to the 650 manifold, mark it to match and grind it out to save $50 on a used one. Not really my idea of fun, but have at it if you insist on recycling your 650 parts.

Here is the different manifolds, the 701 is on the right. You can see the size increase on exhaust porting.

The engine is back in the boat now. It really pays to follow a check off sheet in order when reassembling or installing an engine - with an actual torque wrench and blue loctite. Otherwise be ready to do it the second time right. ;)

Start by pulling off needed components such as Stator, flywheel, starter and moving them to new engine short block.