Any 350 Mariner owners with big blocks?

[MarkGibson61611]

I'm asking for a friend...

I have a buddy with a 1999 (maybe a 2000?) 350 Mariner with MFI 454's... He complains of poor mileage (~0.65/mile at a 22mph cruise) and generally poor performance (27 mph at 4100 RPM). I don't believe the boat is propped correctly (he's doing some research), and he's having difficulty finding anyone with a 350 with big blocks (small block boats abound - and all seem to perform better than his). Anyone out there with this combination that's willing to share his or her experiences?

Thanks & regards,
Mark Gibson

 

[OldMariner32]

I also will be interested to see the replies. I have had twin 351s and twin 350s as well as twin 454s. The boat with the big blocks was a Chris Craft 332 Commander and the lightest cruiser I've owned. The performance and economy were both disappointments. (Ditto for the suburban at work that had a 454.)

 

[dmunneke]

I have a 85 36 mariner with 350hp 454's Unfortunately I believe mine is not propped properly either. My engines run great but underway they wont break free of 3000 rpm's

 

[rich356]

I have a '99 356 Aft Cabin with Mercruiser 7.4L MPI EFI's (454's), and they seem to get closer to 1/mile, but I cruise a little slower than 22 mph (more like 19-20). WOT I get just about to 30 mph. He may have Crusader 454's because my brother-in-law has a '98 350 Mariner and that's what he has. I'm not sure if there are slight performance differences between the two though I would think that given the fact that the 350 Mariner is about a ton lighter than the 356 I would think it would be slightly faster with the same HP, but a lot of other things could affect that. In fact, I think I remember my b-in-law saying that my top speed was slightly faster than his while we were on our sea trial this past weekend. So your friend's engines and props may be fine. Could he be cruising a little too fast? Not sure at what speed the Mariner comes up on plane, but I'll find out.