are these parts compatible?

[Oldstarcraft]

I have a 1979 100 hp evinrude with two bad pistons and badly scored cylinder walls,the model number is 100999s. I have a chance to buy a powerhead from a 1980 150 hp, model number E150TRLCSR my question is if my complete bottom end and power trim/tilt assembly would be compatible with the 150 powerhead.

 

[Dhadley]

Re: are these parts compatible?

The adaptor plate (what the ph bolts to) is different.<br /><br />What would you use for a hood?

 

[Oldstarcraft]

Re: are these parts compatible?

I was hoping to use the hood from the 150 the only parts that seem to be missing from it is the vertical shaft and the bottom gear case. the middle part of the motor is still there complete with trim tilt assembly. I don't know if the bottomcase can take the extra power even if they would fit??

 

[Dhadley]

Re: are these parts compatible?

Ah, OK. Yes the V4 case will bolt up to the V6 midsection. It may not last long but you will have a tremendous holeshot. I have always had good luck using a synthetic gear lube when using a V4 (2:1) case on a V6. <br /><br />I bet your 2 tore up pistons are on the starboard bank of the V4.<br /><br />Good luck!

 

[Oldstarcraft]

Re: are these parts compatible?

Thanks and you're right about the pistons they seem to have developed a ridge around the outside top of the piston which then broke off in pieces (on one exposing the ring) the pieces then scored the sleeve and some made marks in the head.<br />I'm new to this whole outboard thing and $2500 seems like a lot of money to put into rebuilding this powerhead if I can find a used one that runs and will fit my bottom end which is in very good condition. the v6 is not exactly what i was looking for but the price is right.

 

[Dhadley]

Re: are these parts compatible?

What you see before you (on the V4) is typical coking damage. The rings carbon up (coking) and stick in the ring land on the backside oppsite the end gap. As more and more of the ring sticks in, the piston loses support and rocks in the bore. Eventually the pistons rocks enough that the end of the ring shears off.<br /><br />If you hold the piston so the dome is up, I'll bet the ring broke on the right side of the locating pin first. And this happens on the starboard side cylinders first too.<br /><br />This is typical of a "lugged" or "overpropped" (terrible phrase but common) motor. On the V4 and V6 crossflow this happens sooner if the motor is set up so that wide open is at or near 5000 rpm. IE -- if the top rpm is 5000 this will happen relatively quickly. Sometimes in 25 running hours. If the top rpm is around 5500, it will take longer. Possibly twice as long. If its set up at or near 6000 rpm it will rarely happen.<br /><br />Good decarb jobs will definately help avoid this. Good decarbs and good set up will avoid this alltogether.<br /><br />Good luck!