nzjetboating Web Board.

nzjetboating.com Forums => Tech Library => Topic started by: Rich on January 14, 2015, 17:23:02 PM

Title: What motor next?
Post by: Rich on January 14, 2015, 17:23:02 PM
I have an STX 12F carby in my boat and it appears t0 hates me.

It has 177hrs on it and it may have dropped a ring as compression is 120, 90, 120. Before pulling it appart I have been doing some research. If I hone the cylinders and replace pistons and rings this will fix it however the bottom end may go any time.

2nd problem is it has always been a pain in the  ()() to start cold.

I see I have many options from cheap to expensive.
1. Hone, replace pistons rings, and fingers crossed.
2. Full re-build, more expensive still possibly a pain in the  ()() to start.
3. Buy another cheap ski with Direct injection. Same 12F but easier to start and plenty of spare parts such as Pumps ex.
4. Spend heaps and get a 4 Stroke 15F.

What have you guys experienced?
Title: Re: What motor next?
Post by: rogee on January 14, 2015, 18:16:08 PM
Or fit a m16a swift engine .......
Title: Re: What motor next?
Post by: Matthewf/Norbert/TuiDog on January 14, 2015, 18:27:14 PM
get a 15F, you need the revs for performance on that unit
Title: Re: What motor next?
Post by: Jeff B on January 14, 2015, 19:51:15 PM
Is it a 2 stroke 3 cylinder? If so it's not an STX 12f but an STX 1200.What year is the engine? Approx 2001?
Might pay to check if it has nikasal bores, if it does then they are not supposed to be honed. If the bore is damaged then the cylinder needs to be replaced or re-plated which is not cheap C""
Title: Re: What motor next?
Post by: Rich on January 15, 2015, 01:00:40 AM
It is the 3 cylinder 2 stroke from a 1998 stx.
I have done some more research and found the error of my ways. if I want to go 4 stroke I can do the 12f or 15f.
Any ideas how I can get a cheap 15f. Only way I can see is buy a $8k ski?
I can get an stx 2001di for about $5k?

I may be able to sell some parts to make some money back I supose.
Title: Re: What motor next?
Post by: Rich on February 17, 2015, 00:10:03 AM
It appears that the 15f will not fit without major modifications.
Does anyone know the engine mount spacing dimensions of the 12f?
Title: Re: What motor next?
Post by: Matthewf/Norbert/TuiDog on February 17, 2015, 09:50:43 AM
replacing engines you will always need mods

i would suggest you rebuild motor, sell boat and get a alloy hull etc...(glen is selling his!)