1999 175hp EFI merc Nitro edition. Massive torque no top end. with 26pitch prop

[machinist]

Hello I have a interestion question that my mercury tech cant answer. I ran this boat (99 nitro 884 savage) for 2years all the time. Great running motor! ran a 23 tempest plus. With this prop it would take bout 8-10 seconds to come up with 2 people and a tournament load and run about 67 with a 26 tempest plus it would take a loooong time to get up but would run upper 70's mph. The boat set for a year while i fished out of another. pulled it back outta the garage took it to merc tech had them do full tune,power tune, change everything out and do compression check everything speced out perfect. THis is long story but keep reading. Took the boat to the water month back with the 23 pitch. I came up instantly with 3! people in the boat and a tournament load but topped out at 50mph. I thought heck maybe i need to grab more water to grab some speed but knew something wasnt right. I put a 26 tempest plus on it with 2 people and a tournament load it jumped out of the hole in 8-10 seconds!! but only ran 65 mph. This motor has gained some awsome torque but no topend? Any comments?

 

[Faztbullet]

Re: 1999 175hp EFI merc Nitro edition. Massive torque no top end. with 26pitch prop

Did the WOT rpm change also???

 

[CharlieB]

Re: 1999 175hp EFI merc Nitro edition. Massive torque no top end. with 26pitch prop

Ignition timing is critical to performance, however, too much timing will kill a motor with little to no warning.

Factory settings on older motors were fine, then, but with the fuels today, and the addition of alcohol in most places, we have found it much safer, for the motor, to reduce timing by 2 degrees.

Your mechanic is wise to adjust your motor for todays fuel, reducing the possibility of piston destruction from spark-knock caused by advanced timing.

The trade off is better acceleration out of the hole, at the loss of a little top end.

Be happy about it, he may be saving you the cost of a rebuild.

 

[machinist]

Re: 1999 175hp EFI merc Nitro edition. Massive torque no top end. with 26pitch prop

lost 250 rpms somewere along the way it tops at 5250 now instead of about 5500 rpm at WOT. I didnt mention it because it seems 250 rpms would not dracticly decrease my top end..?

CharlieB your are correct, and was a question that was asked he said that he didnt do anything different to the timing he wants the boat back to look at it cause he claims it doesnt make since but its hard to but a boat in the shop that you can fish out of.
If the timing is adjusted on a motor do you think that i would see the dractic difference in the motor preformance of 10 mph top end?

 

[CharlieB]

Re: 1999 175hp EFI merc Nitro edition. Massive torque no top end. with 26pitch prop

Timing IS power, power keeps increasing as you increase timing, until you crush a piston, so we have to decide, do you want to go screamingly fast at the risk of breaking the motor? OR tune it to provide decent, respectable power AND last?

Are you fishing or racing?

How fat is your wallet?

 

[Faztbullet]

Re: 1999 175hp EFI merc Nitro edition. Massive torque no top end. with 26pitch prop

Sounds like technician either misadjusted TPI or set timing with bia's/advance circuit connected. You motor should have a detonation module and sensor to help prevent damage...