Z275 Top Speed
 

I have a 2001 Z275 7.4L GSi DP rated at 405hp. I am working through some other issues (see thread in maintenance forum) but right now I am topping out just under 50 MPH on GPS with about 4500 RPM. Seems like I should get a little more speed / RPMs out of her??? Any other thoughts or experience anyone can give will be appreciated!! (motor all stock except for the additional of a K+N flame arrestor)

I'll update any changes in performance when I get my hot start issue resolved.

Thanks

Tom

Re: Z275 Top Speed
 

Hey Tom! Did you get my reply to your post on Facebook?

Re: Z275 Top Speed
 

Got it, will keep in touch. I hope to have some pics on sometime in the next few weeks, I'd like to see more of you 275 as well - Thanks


Tom

Re: Z275 Top Speed
 

Hi Tom,
I have a 2001 Z275 with a Volvo Penta 7.4Gi rated at 310hp with a Volvo Penta DPS Drive and F5 Prop.

I get about the same top speed as you do, max 48mph, at 4250 rpm.

I would be very interested to know what prop you have.

I was considering re-powering by boat next winter to an 8.1 GXI at 420hp an I would have expected to get well in to the 50's with that.

Regards,
Barry

Re: Z275 Top Speed
 

Hey Barry! Thanks for the info. I need to check what prop setup I have. Boat is on a slip / lift at our local lake so it is hard to get back to theoutdrive without swimming to check the numbers. I am pulling it out to go to TablerockLlake next week and will check it out then. Not sure what my max RPM should be but I would think I should be running into the 53-55 MPH range with the 405 HP GSI?? As I said I have a hot start issue that is baffling me and depending on what we find with that it may give me a little more top end when the problem is solved!

I'll let you know when I get the numbers from the props.
:wink_thumbup:

Thanks

Tom

Re: Z275 Top Speed
 

Tom,
The max rpm is marked on the engine on a sticker with other information on it.

I read about your problem with the warm starting. Have you checked your manifolds and risers to make sure water is not getting back into the cylinders?
I recall a similar problem with my own engine that was traced back to this.
I am assuming you have checked plugs, leads, distributor etc.

Barry

Re: Z275 Top Speed
 

I had the upper manifold off this spring - but that was before I got it out for the season so of course all was dry, and it looked ok then??? (I had the injectors sent out for rebuild thinking I had a leaky injector that was draining down the fuel into the engine from the fuel rail when it was shut down - they did find a dirty / leaky injector but my problem is exactly the same after) Plugs are my next check, I had full intentions to replace them but I ordered the wrong ones (GSi not GS - they're different... duh) and I never got back to that item as I was battling an IAC valve that one of the pins came off at the connector due to corrosion when I took the manifold off - didn't notice the broken pin and wouldn't idle after putting back together - so I wasted a couple weekends focused on that until we found the problem and replaced the IAC and plug.

So now I am going to change the plugs this weekend and take a look at the old ones - hoping it is something simple like the plug being bad from the cylinder that had the bad injector... If only it can be that simple...

Thanks for the advice and I'll let you know...

Tom

Re: Z275 Top Speed
 

I tested it again today after getting my spedo working. I was reading 46 mph on my gps and spedo with 10 people (and one little dog) onboard in a light chop. I was pulling 5K rpm's but not sure if it reads correct. I have to "thump it" quite often!