nissan 25 four stroke to 30 hp?

[pvanv]

Re: nissan 25 four stroke to 30 hp?

Verify timing advance.

 

[garbuster_0285]

Re: nissan 25 four stroke to 30 hp?

Well I think I figured it out. After looking at the spec. book It looks like I am going to have to buy 3 carbs. The air jet hole is different on the carbs(a part made on the carb). Well I guess Ill put my 25 hp parts back untill I have $600 to dish out for new carbs.

 

[HJFF1969]

Re: nissan 25 four stroke to 30 hp?

What do you mean with "The air jet hole is different on the carbs(a part made on the carb)" if it is a part could you replace it or is the part the whole carb?

 

[garbuster_0285]

Re: nissan 25 four stroke to 30 hp?

well it shows that in the book that there is a a Main air jet and a slow air jet which are not parts found in the parts guide for the carb. So it makes me think that it is something in the carb body. It says the main air jet on a 25 hp is a #125 and the 30 is a #130 and the slow air jet on a 25 is #95 and a 30 is #85. I cant find this part on the carb parts breakdown. must be on the carb body?

 

[John_S]

Re: nissan 25 four stroke to 30 hp?

Buying new carbs or risking modifing the existing for 5HP seems to be allot of effort/money for very little gain. Time to plane will not change, and only probably a couple/few of mphs at wot. I suspect that you might be trying to compensate for an underpowered boat, which is taking too long to plane. I'd hate for you to go through more expense and not get what you think it will provide.

 

[garbuster_0285]

Re: nissan 25 four stroke to 30 hp?

Well I am not sure how much faster it will be. I am a bowfisherman and rod and reel fisherman. I have a deck I put on the front that weighs about 200lbs. I thought maybe the 30 would help pushing the boat better with the deck on it. I thought I might get 5mph out of it.

 

[210bert]

Re: nissan 25 four stroke to 30 hp?

Well I tried it just a while ago and wish I would have found this posting. I changed the 4 parts in each of the 3 carbs also. It ran slower, harder to plane out, slow acceleration, and used twice the fuel. What a dog it was. There has to be something different between the carbs also. Well live and learn. It had to be a problem with the fuel/air mixture. WHaaaay to rich. I hope this helps some one. OH, and if some one wants to try it again I will sell them the parts real cheap.

 

[pvanv]

Re: nissan 25 four stroke to 30 hp?

The carbs for the F30A are bigger. More air, and more fuel. So if you put the big jets in a 25, you did not add any air... you flood the engine in fuel, resulting in your situation. If you really want to bump it to a 30, you can change all 3 carbs and then verify timing is correct. Generally not cost effective.