25 to 35hp johnson

[14apache]

Would like to know if pluging the bleed hole in the cylinder to the exhaust will cause a problem or help the performance. I did some clean up on the ports with a rotary file. I have boysen reeds would like to know what else would help the top end performance. Thanks Eric

[Fastjeff57]

No difference, for that tiny holes is open only a fraction of a second at speed. Any exhaust leaking out doesn't count.

Jeff

[14apache]

The hole is .160 diameter it starts at .800 down from deck and the exhaust is 1.6 down from deck. Im not shure why they put the hole there. Compression loss at low speed. Thanks Eric

[Fastjeff57]

The hole makes pul starting a bit easier by bleeding off compression. At speed, the hole isn't open long enough to affect power.

Jeff

[speedfreak]

14apache, Did you perform a 25 to 35 conversion on your motor? I have the same 25hp johnson motor and have converted it from a 25 to a 35, I also put boyseen reeds in. I would like to know what all you did to yours to convert it. Do you know if the heads are different 25hp vs. 35hp, maybe port timing was different between them? PM me if you want. I'm not sure if I got everything during the "conversion". I was told the only difference between the 25 and 35 was larger pistons, larger carb jets, and a slight advance in the timing!

The dealership that did my conversion said plugging the bleed hole would not help performance.

[JohnsonM50]

[QUOTE=14apache;121053]Would like to know if pluging the bleed hole in the cylinder to the exhaust will cause a problem or help the performance. I did some clean up on the ports with a rotary file. I have boysen reeds would like to know what else would help the top end performance. Thanks Eric
Ive read something about pressurizing the exhaust chamber to slow the exit of new fuel . Not that motor tho so maybe unrelated & just a bleed off as written.

[Fastjeff57]

Pluging that bleed hole makes NO difference on power output; it just makes it harder to pull start.

Jeff

[14apache]

The head is not the same the chamber is wider at the deck i think for piston clearnce. I added larger carbs made a intake on bridgeport and angled the case for a straighter flow. + stuffing crank case. Will see soon.

[speedfreak]

Thanks, I thought there had to be more to a 25hp to 35hp conversion than larger pistons, larger jets and a couple degrees of timing. Thanks 14apache for the info. Any other notible differences between the two?

[14apache]

Anyone else try anything with good results? Mine is on a zodiac yl340 running 37mph needs more prop and the bigger carbs