Supercharge gti 155 04 model

[zmilos]

Hi guys Im about to install and supercharge gti 155 engene in to my 04 mod seadoo gtx limited 185 I have a ski that blow engene and I menaged to secure gti 155 block with all internals in tact inc flat pistons.I rebuild the top end inc different front Cower to ad supercharger we changed the flywheel to the 86 tooth And planing to use red supercharger.need some advice on whether this will run being a high compression engene. Planing to use the red supercharger and no intercooler Any imputes on what I need to do additionally to make this a stabile Ski ,the rest of the stuff will be the same as what it was before standard ECU and jet pump was rebuilt as well using standard prop All imputes welcome Thanks

 

[IDoSeaDoo]

So let me get this straight: You're going to use a 155 non-SC engine and add the SC. I'm certain that both the 155 and 185 both had cast (not forged) pistons, but I'm not sure if that makes them the same piston. I would think that the SC piston would have a concave surface to accommodate for the extra compression. I'd do my homework on that one. Also, use your 185hp fuel injectors and fuel pump, as I believe the fuel pressure regulator had a different pressure setting than the non-sc.
What happened to your original engine? I'm using the 2004 185hp in my boat, and want it to last forever
Did you ever have the RPM surging issue? Mine will surge at all throttle positions up to 3/4. Super annoying, and I'm not sure how to isolate it down to one component.

 

[Coastiejoe]

SC engines are a lower compression engine as compared to Non-SC engines. Not saying it won't work, but it will likely cause issues.

 

[zmilos]

I completed the built last week the engene started first go it runs well no issues at the moment need to test it out on the lake
This weekend will keep you posted

 

[zmilos]

So let me get this straight: You're going to use a 155 non-SC engine and add the SC. I'm certain that both the 155 and 185 both had cast (not forged) pistons, but I'm not sure if that makes them the same piston. I would think that the SC piston would have a concave surface to accommodate for the extra compression. I'd do my homework on that one. Also, use your 185hp fuel injectors and fuel pump, as I believe the fuel pressure regulator had a different pressure setting than the non-sc.
What happened to your original engine? I'm using the 2004 185hp in my boat, and want it to last forever
Did you ever have the RPM surging issue? Mine will surge at all throttle positions up to 3/4. Super annoying, and I'm not sure how to isolate it down to one component.

Yes I’m pushing abut 8 to 10 psi ( using black 16 tooth SC) into the flat pistons not shore what this will do to it but I’m planing to take it ezy to start with.
Would the engene be more responsive and effective or will it overheat at higher revs ,the old engene destroyed it self only the
Head lived I was chasing Replacment block for it with no success
and then came across gti 155 block

 

[zmilos]

Hi guys and thanks for the impute I put the ski back together two days ago and it started first go after
been in peaces for over 2 years engene runs fine it’s idling steady and I raved it up to around 4500 on hose
It will run on 98 octane only as fuel is cheep down under . Im planing to add intercooler to it but for now just want to
run it and see if any other issues will come up. I know that the pistons in it are a week link but I’m planing to add some
Other mods to it to keep better monitoring on the head temperature.
How do I recognise pinging in the engene ? And what roll play the injectors and SC boost to it? should I stay away from
Running it flat stick for longer than say 5 min . If I can make this unit a reliable steady ski then the project would be success
Im not really interested in performance and top speed if I can achieve 50 to 55 mph on flat that would be top

 

[IDoSeaDoo]

You'll get closer to 60, maybe 63 on a stock GTX ltd. With higher compression, you may get there faster. You could have used a taller head gasket to compensate for the flat-top pistons, but I guess it's too late for that. I'm not sure you should add an intercooler, as that would put even more of an air charge into the motor. You've already got higher compression than is warranted. I would stick with that high octane fuel though. Who knows, you might be fine. I bet it's gonna be a screamer!

 

[Coastiejoe]

What size injectors are in the engine at this time?

 

[zmilos]

You'll get closer to 60, maybe 63 on a stock GTX ltd. With higher compression, you may get there faster. You could have used a taller head gasket to compensate for the flat-top pistons, but I guess it's too late for that. I'm not sure you should add an intercooler, as that would put even more of an air charge into the motor. You've already got higher compression than is warranted. I would stick with that high octane fuel though. Who knows, you might be fine. I bet it's gonna be a screamer!

I hope it will run well I have a small issue when i run it on hose
The other day after raving it up to about 4500 -5000 when the
Engene drops down to idle it starts to run unsteady and die down
After restart idles normal , any idea ?
I did have 10 litres of old fuel in the system that was about 2 years old
Didn’t pump it out just added extra 10 L of fresh 98 octane

 

[zmilos]

What size injectors are in the engine at this time?

Im using the same injectors that gtx lim 185 came with
Don’t if I need to use different ons and what would that do to
Performance
Tnx

 

[IDoSeaDoo]

If the only thing you're changing is the pistons, the injectors should be okay. As for the revving problem, do you have too much oil in there? These motors are very picky about how much oil you put in. There is a special procedure to check it too. Also, make sure your PCV system breathes well by pulling the oil dip stick when it returns to idle. If you don't get a big release of pressure, you're fine. These engines produce a TREMENDOUS amount of blow-by. At least mine does. You, with the higher compression will probably produce even more. Did you ever get a compression reading after getting it all back together?