Impeller tolerance

[smackdaddy53]

Crankshaft bearings are about to go, they are rattling and causing the motor to run a little hotter than normal- 150-160 degrees. Still can't get max rpm's and he convinced me the motor would definitely be underpowered on my boat even if it ran right. I am selling this motor and either buying a used 90 or 115 jet or just biting the bullet and getting a brand new 115 4 stroke Jet. Damn things are 400# but I think my draft should not change much more than an inch or so. I am also considering either lithium batteries or just taking out one optima and running off one cranking/house battery to lighten the load.

 

[dhoganjr]

I was hoping you would get better news and it would be something simple. But at least now you know what the problem is.

Since you are going to replace it, unless you can find one in excellent condition and know the history, I would go with a new one if you can afford it. Jets are usually run hard often hitting bottom and clogging up cooling passages and are usually run in the higher rpm range through most of their life. Most of the used ones were put on underpowered boats and upgraded to a bigger size later shortening their usable life as you have found out. If a used one is very new and well taken care of they usually want a pemium price which is not far from new.

Don't know which way your going, but a Yamaha 115 Fourstroke weighs 402 according to their website. The new Mercury 115 Fourstroke weighs according to the site 317, but it has moved around I think it weighs more, the prop version weighs 359 so I would guess it weighs around 340.
I have heard good reviews with this new design. With either option you get a 3 yr warranty for peace of mind and with a promotion you can usually get a 5 yr and can extend it to 7 yrs.

A 115 Fourstroke should jump that boat on plane in about a boat length and get between 35-38 mph. You will be able to cruise about 2/3 throttle easily and it will sip fuel and be quiet running.

My choice would be the new route and you can get financing on them if you need to. I bought my first one used and the other 2 new. Buying new I know it was broke in correctly and well taken care of. If you decide to get a new one follow the break-in schedule by the book, explains it in the manual.

Just my .02 worth, give you something to think about. I ran my Mercury 115 Fourstroke for 11 years, so if you have any more questions ask away.
Keep us updated on whatever you decide.

 

[smackdaddy53]

I appreciate you guys input for sure!
The mechanic offered $1200 for my motor as-is but I think I will ask more for it because I have over $800 in brand new parts in it plus a new stainless impeller and liner I never installed. The pump with new bearings and impeller is alone worth at least $1800. That is a nice chunk of change to help the "ouch" of purchasing a new motor.
I would love to find a new Yamaha 115 or 90 2 stroke but that is nearly impossible. I want the warranty.
I will definitely check out the 115 4 stroke Mercury. Just the peace of mind I would have with a new motor would be well worth the price. The weight is not ideal jumping from drafting 6" with my 250# motor to at least 350# but I suppose once I'm on plane it won't matter much. I just want to draft as little as possible and jump on plane fairly quickly (in an ideal world there would still be light and torquey 2 strokes available).

 

[dhoganjr]

With your pods I don't think your going to lose very much draft, except when standing on your platform of course. You may be able to offset this by moving anything forward that is possible. I would say 8" at most on draft and with a Fourstroke unless you are running long distances, you can go light on fuel for short trips.

 

[smackdaddy53]

With just me on the rear seat and 5 gallons of gas the stern squats a little over the 6" first step of the pods. If I put more fuel in the bow tank the draft equals out more and actually makes the stern raise up a little. With 15 gallons of gas I draft about 6", maybe 7 at most. We will see because either way I have to have more power!