311 Speed with 502's?
Gold Member
07-29-2013, 07:31 PM
#12
Registered
Join Date: Nov 2006
Location: Great Sacandaga Lake, NY
Posts: 1,261
Likes: 0
Received 1 Like
on
1 Post
I have a 1993 336 with 502s approx 425HP a side. Turning 24P Bravo 1s best speed 65.5 GPS at 4800. Ran 67-68 at 5000 with 25P Mirage. 24s will get to 4500 quicker than the 25s. Problem is too much stern lift for me..
09-18-2013, 11:01 PM
#13
Registered
Thread Starter
Join Date: Mar 2011
Location: Rochester, NY
Posts: 88
Likes: 0
Received 0 Likes
on
0 Posts
I had a chance today to try different prop set ups. And GPS is working now.
First run for reference with B1 24's at 5000 RPM was 64
Put on B1 26's. Couldn't turn them. It (way) longer to get to speed and saw 63 at 4500 RPM
Back to 24's turning in and saw 63 at 5000 RPM. Cruising with shifters in reverse is weird by the way!!!
I did notice that drives have about 3" of play back and forth independent of each other and no, I do not have a tie bar. Would that shave a lot of speed?
Also, the port motor is a but low at 5000 when the starboard motor is at 5100. Don't know if this is a motor thing or if 23 Yr old gauges just don't quite read accurately.
My other thought is these boats really don't go 70 with stock 502's, and I'm chasing a ghost LOL!
Happy to hear your thoughts guys.
Any thoughts?
First run for reference with B1 24's at 5000 RPM was 64
Put on B1 26's. Couldn't turn them. It (way) longer to get to speed and saw 63 at 4500 RPM
Back to 24's turning in and saw 63 at 5000 RPM. Cruising with shifters in reverse is weird by the way!!!
I did notice that drives have about 3" of play back and forth independent of each other and no, I do not have a tie bar. Would that shave a lot of speed?
Also, the port motor is a but low at 5000 when the starboard motor is at 5100. Don't know if this is a motor thing or if 23 Yr old gauges just don't quite read accurately.
My other thought is these boats really don't go 70 with stock 502's, and I'm chasing a ghost LOL!
Happy to hear your thoughts guys.
Any thoughts?
09-19-2013, 12:49 AM
#14
Registered
Join Date: Aug 2005
Location: Between A Womans Leggs in IL
Posts: 6,306
Likes: 0
Received 1 Like
on
1 Post
I had a chance today to try different prop set ups. And GPS is working now.
First run for reference with B1 24's at 5000 RPM was 64
Put on B1 26's. Couldn't turn them. It (way) longer to get to speed and saw 63 at 4500 RPM
Back to 24's turning in and saw 63 at 5000 RPM. Cruising with shifters in reverse is weird by the way!!!
I did notice that drives have about 3" of play back and forth independent of each other and no, I do not have a tie bar. Would that shave a lot of speed?
Also, the port motor is a but low at 5000 when the starboard motor is at 5100. Don't know if this is a motor thing or if 23 Yr old gauges just don't quite read accurately.
My other thought is these boats really don't go 70 with stock 502's, and I'm chasing a ghost LOL!
Happy to hear your thoughts guys.
Any thoughts?
First run for reference with B1 24's at 5000 RPM was 64
Put on B1 26's. Couldn't turn them. It (way) longer to get to speed and saw 63 at 4500 RPM
Back to 24's turning in and saw 63 at 5000 RPM. Cruising with shifters in reverse is weird by the way!!!
I did notice that drives have about 3" of play back and forth independent of each other and no, I do not have a tie bar. Would that shave a lot of speed?
Also, the port motor is a but low at 5000 when the starboard motor is at 5100. Don't know if this is a motor thing or if 23 Yr old gauges just don't quite read accurately.
My other thought is these boats really don't go 70 with stock 502's, and I'm chasing a ghost LOL!
Happy to hear your thoughts guys.
Any thoughts?
10-24-2013, 02:47 PM
#15
Registered
VIP Member
I had a chance today to try different prop set ups. And GPS is working now.
First run for reference with B1 24's at 5000 RPM was 64
Put on B1 26's. Couldn't turn them. It (way) longer to get to speed and saw 63 at 4500 RPM
Back to 24's turning in and saw 63 at 5000 RPM. Cruising with shifters in reverse is weird by the way!!!
I did notice that drives have about 3" of play back and forth independent of each other and no, I do not have a tie bar. Would that shave a lot of speed?
Also, the port motor is a but low at 5000 when the starboard motor is at 5100. Don't know if this is a motor thing or if 23 Yr old gauges just don't quite read accurately.
My other thought is these boats really don't go 70 with stock 502's, and I'm chasing a ghost LOL!
Happy to hear your thoughts guys.
Any thoughts?
First run for reference with B1 24's at 5000 RPM was 64
Put on B1 26's. Couldn't turn them. It (way) longer to get to speed and saw 63 at 4500 RPM
Back to 24's turning in and saw 63 at 5000 RPM. Cruising with shifters in reverse is weird by the way!!!
I did notice that drives have about 3" of play back and forth independent of each other and no, I do not have a tie bar. Would that shave a lot of speed?
Also, the port motor is a but low at 5000 when the starboard motor is at 5100. Don't know if this is a motor thing or if 23 Yr old gauges just don't quite read accurately.
My other thought is these boats really don't go 70 with stock 502's, and I'm chasing a ghost LOL!
Happy to hear your thoughts guys.
Any thoughts?
09-09-2024, 05:32 PM
#16
Registered
Join Date: Sep 2024
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
I have a 90 311 with MPI 502’s I was wondering what is the diameter of your prop. I’m running a 27 pitch three blade right now and I’m getting about 68.
Today, 11:16 AM
#17
BEACH PARTY / HOLLOWPOINT
Platinum Member
The MPI 502 was not original to the boat. Is this a Bravo setup or was it originally a 420 TRS boat (I think you could still get a TRS 311 in 1990).
The documentation that I have from Formula says that the 390 horse 502 Magnum/Bravo runs right at 69 MPH (radar) at 5k RPM. It did not have the prop listed, but my guess was that it was spinning a 25P Mercury Mirage 3-blade (23P would overrev I'm pretty sure).
My 88 had 502 MPI 415s and it ran 69-71 depending on water , weather, and weight. I had to trim the drives (TRS) way off the scale to get there and it took a lot of room to do it. RPM would typically run right at 4700 with a 27P Mirage maybe a tad more.
The 311 with its rocker hull needs a lot of power, trim, and rougher water to go fast. Friends with some pretty strong 311s have come to me saying their boats are supposed to run upper 70s/low 80's and could only get low 70's out of them and no RPM. I would ask about where they were trimmed up and they'd say about 6, 7, maybe 8 on the indicator card. I would tell them to trim it to where it starts to fall off and then bring them back in a touch - basically way off the scale. When the stern gets light and starts to dance around a little, you're in the zone. Over a good distance there's another 5-6-7 MPH to be had. I very much recommend having hydraulic steering on these boats.
The documentation that I have from Formula says that the 390 horse 502 Magnum/Bravo runs right at 69 MPH (radar) at 5k RPM. It did not have the prop listed, but my guess was that it was spinning a 25P Mercury Mirage 3-blade (23P would overrev I'm pretty sure).
My 88 had 502 MPI 415s and it ran 69-71 depending on water , weather, and weight. I had to trim the drives (TRS) way off the scale to get there and it took a lot of room to do it. RPM would typically run right at 4700 with a 27P Mirage maybe a tad more.
The 311 with its rocker hull needs a lot of power, trim, and rougher water to go fast. Friends with some pretty strong 311s have come to me saying their boats are supposed to run upper 70s/low 80's and could only get low 70's out of them and no RPM. I would ask about where they were trimmed up and they'd say about 6, 7, maybe 8 on the indicator card. I would tell them to trim it to where it starts to fall off and then bring them back in a touch - basically way off the scale. When the stern gets light and starts to dance around a little, you're in the zone. Over a good distance there's another 5-6-7 MPH to be had. I very much recommend having hydraulic steering on these boats.
The following users liked this post:
Padraig (Today)
