Nissan 9.9B2 Thrown rod is there a reasonable fix?

[lepark]

Hi. I should have posted a question to the experts a week ago to possibly avoid my present situation but took motor out one last time while waiting for service manual Now have a broken crankcase ,connecting rod, slightly scratched piston cylinder and scratched/pitted camshaft.I love the motor and would like to keep it if cost not too excessive

Is it possible/reasonable to take the case to a skilled aluminum welder to fix or do i really need a new crank case? I have the piece(about 1/3/4 inches in length) that was broken but there is another crack to the left of the hole. Is it possible to just buy a crank case somewhere or do you need to buy the case and cylinder? I see around 700 for both

The piston cylinder has small visible scratches on the right very near the cam side which i cannot feel when i run my finger over them. The scratches on the camshaft i can feel. They are under where the connecting rod cap was. Is it necessary or as simple as honing the cylinder or would it be okay leave as is. How about the cam? Sand and polish?

Finally, my original problem was the motor would sometimes bog down when tryingto increase speed after idling at low speed for a while in neutral or forward gear. If i would stop the motor and restart and rapidly go forward and increase speed no issues. This started a few weeks ago, Though I had fuel problem ,always empty carb after every use, and was getting the service manual to clean/rebuild.

Yesterday No problem with the idling to higher speed but once lost power while at higher speed and regained when slowing throttle and i could increase speed again with no problem. still thought fuel/carb problem. Then while at moderately high speed heard engine revving and rod broke. is it obvious that is is not fuel as the cause or highly likely something else? Valve? I did notice the color variation of the valves in the cylinders. If i do go through the cost and trouble to fix damage without fixing underlying problem

Thanks for taking the time to read and help. My friend has also received help from this forum and sent me here.

Lee

 

[pvanv]

Crankshaft is shot, block is shot, rod and piston huffed, cam bad. You could replace the short block, but it will not be cheap.

3H8B870902

SHORT BLOCK (9..9B/15B/4-ST)-NEW STYLE

$2115.65

Essentially, you have scrap, as the parts and labor to fix it would far exceed the cost of new.
Better to see if you can find a used motor and go through it. Pistons, rings, etc., are all available.

A new 9.8 (carbed) would run you under $2000. A new 9.9 EFI would only cost a few hundred more, depending on shaft length, whether electric start/remote, etc.

 

[ahicks]

Being the back yard shade tree mechanic that I am, I would look for a used short block (ebay). There is little doubt this won't be much fun to change, but approached with a good manual and a high degree of patience, it's very "do-able". Would be a good project for somebody that's handy, and with more time than money (like a retiree for instance!).

 

[km1125]

I think your best route is to part it out and just buy a replacement. You could buy the same used motor for ~1000 and even put a few hundred into prepping it (water pump kit, carb cleaning, etc) and then by selling off the good parts on the existing motor recoup most of what you spent. The lower unit alone is worth several hundred and probably would go pretty quick. If you had electric start you could either re-use it on the "new" motor or resell that as well for ~100. Probably lots of other parts like the manual start mechanism would be useful to others as well.

Also note that if you went the brand new route, while a bit more expensive you also get the advantages of fuel injection and about 20-25 lbs less weight for the same output.

 

[lepark]

Thanks for the insightful responses and guidance. Fears confirmed and glimmer of unrealistic hopes appropriatey crushed. Frustrated that i didnt delve into the issues sooner and paying the price

Will likely keep the old motor for a while to see if anything shows up. Have free time and enjoy learning and tinkering.

Will also buy a new motor electric start probably with efi

Thanks again

l

 

[raczekp1]

its posible to fix this bad powerhead.
just weld the block,
hone cylinders
buy new( con rod. bring both con rod and crankshaft to mashine shop to polish con rod jurnal and fit con tod ends to crankshaft.
in my area work+ weldind would cost less than 100$

 

[lepark]

Thanks for the reply.

I do plan on resurrecting this motor at some point and I guess I am still wondering about the initial problem i was having with the the motor bogging down/missing on occasion going from low speed to high speed but not when going rapidly into forward and rapidly accelerating and then the recent problem missing/revving at higher speed and then able to decrease the thottle speed to resume normal function then able to accelerate as normal.

Dont want not want to put in more time and effort and not fix or feel comfortable about the initial problem. ? problem with carb, valves, cam. Being a novice I did not want to be missing what would be obvious to the professionals or experienced.

Thanks again

 

[km1125]

I'm curious how the engine over revved. Do these not have a rev limiter on the ignition side?

 

[lepark]

Im not sure either. Per the manual it does have the ESG. After reading a little more about the ESG it seems that it may have been active at times.during my last trip. Did not notice the oil light, prop issues etc but I was also ignorant enough to not recognize that i should slow down