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Repowering 253 Convincor
- Thread starter Nick616
- Start date
I'm sure the 21 will be too small - but its all I have and what I ran last year - so I at least have a baseline on performance. The 21 is a Solas prop, so completely different design from the Hydromotive - closer to a Bravo.
Just waiting for it to be not too cold ( Lake Michingan doesn't get warm until July ) and not too rough to get some time on the boat.
Just waiting for it to be not too cold ( Lake Michingan doesn't get warm until July ) and not too rough to get some time on the boat.
corey331
Well-known member
If I'm not mistaken, you should be getting 400-500 more rpm out of it than that. 4800 is where my old peanut port 310hp 454 revved to and I got 61mph out of it with a 22p Bravo1.
Edit: I guess I should take into consideration that you have a brand new motor that is still breaking in. That being said, you should still be seeing much more than what you are. That should be a 67-69mph boat in my opinion.
Edit: I guess I should take into consideration that you have a brand new motor that is still breaking in. That being said, you should still be seeing much more than what you are. That should be a 67-69mph boat in my opinion.
Engine "red line" is 5000rpm, rev limiter is at 5150. ( According to the owners manual. )
Prop slip calculates at 17% - I don't know what % is a good number though . . .
Will probably be playing with props - but I'm not as concerned with top speed as I am with cruising speed / efficiency, getting out of the hole with a fully loaded ( overloaded ) boat.
Prop slip calculates at 17% - I don't know what % is a good number though . . .
Will probably be playing with props - but I'm not as concerned with top speed as I am with cruising speed / efficiency, getting out of the hole with a fully loaded ( overloaded ) boat.
Got out last night with the 21 Solas Prop - it actually ran faster than the 23 Hydromotive - hit 60mph at 4800 rpm. (WOT - drive trimmed up about as far as I dared )
Generally I like the Solas prop a lot better - came up on plane faster and easier, boat seems to handle about the same, higher overall speeds. ( I think it is using less fuel at the same speed, but I didn't record the fuel use for the Hydromotive. . . )
I'm wondering if the rev limiter on the engine is kicking in? Seems odd that both props hit the same RPM at WOT.
Generally I like the Solas prop a lot better - came up on plane faster and easier, boat seems to handle about the same, higher overall speeds. ( I think it is using less fuel at the same speed, but I didn't record the fuel use for the Hydromotive. . . )
I'm wondering if the rev limiter on the engine is kicking in? Seems odd that both props hit the same RPM at WOT.
So I got a 20" Solas HR Titan 4 - it was only $300 brand new - got a test run in last night.
61MPH, 5100 RPM
Better out of the hole, more acceleration. I've been really happy with the overall performance of these props.
I would like to try the Bravo 1, but don't want to spend the $ ( $100 from BBlades ) for a test - maybe some time in the future will get a chance to borrow one. . . .
The only thing I don't like, and I don't know if it is hull or prop related is trying to calm the porpoising. Boat runs fine on flat water up on plane. But haven't found the secret on Lake Michigan. Last night was mostly 1' rollers / boat wakes / mess. Couldn't get the boat to run flat, kept bouncing over the rollers. Added tab trim to bring the nose down that helped, but still not as smooth as I would have liked. Had to be careful not to get too much tab or it would start to bow steer a little . . .
Don't know if different prop would help, better trim tabs, or if its just the design of the hull, or just the wrong combination of wave conditions.
I think it ran better a few weeks ago with 1-3' with some chop on top. . .
61MPH, 5100 RPM
Better out of the hole, more acceleration. I've been really happy with the overall performance of these props.
I would like to try the Bravo 1, but don't want to spend the $ ( $100 from BBlades ) for a test - maybe some time in the future will get a chance to borrow one. . . .
The only thing I don't like, and I don't know if it is hull or prop related is trying to calm the porpoising. Boat runs fine on flat water up on plane. But haven't found the secret on Lake Michigan. Last night was mostly 1' rollers / boat wakes / mess. Couldn't get the boat to run flat, kept bouncing over the rollers. Added tab trim to bring the nose down that helped, but still not as smooth as I would have liked. Had to be careful not to get too much tab or it would start to bow steer a little . . .
Don't know if different prop would help, better trim tabs, or if its just the design of the hull, or just the wrong combination of wave conditions.
I think it ran better a few weeks ago with 1-3' with some chop on top. . .
Gimme Fuel
Well-known member
What speed are you cruising at where it porpoises? Under 40-45 mph? I usually cruised at 45-ish to eliminate the porpoise. The hydromotive prop brought the porpoise speed down to about 35 mph but required much more trim at WOT on that boat. Unfortunately that hull isn't very good at slow cruising. Usually my cruise speed has always been 45-50 mph and no issues there using a bit of trim too.
Last night ( and last time out with similar water conditions ) "Cruising" at around 40 mph - 3500rpm was a little rough/bouncy. Dropping to 3200 / 35 MPH made it more comfortable.
I don't think its actually a porpoising problem - its not a cyclical bouncing - its more just the right ( or in this case wrong ) combination of wave height / distance / angle that makes it uncomfortable.
I tried going faster, but would then hit a randomly large wave which made the wife uncomfortable . . .
I don't think its actually a porpoising problem - its not a cyclical bouncing - its more just the right ( or in this case wrong ) combination of wave height / distance / angle that makes it uncomfortable.
I tried going faster, but would then hit a randomly large wave which made the wife uncomfortable . . .
My boat is the same way when there are waves 40 MPH PLUS smooths out the bounce. I have found the Bravo one 4 Blade works great on my boat. I would think it would work well on yours.
Looking back at a year ago - this April 15 we had winter storm Xantu bring 2" of sleet, snow, freezing rain - 28 degrees 
Hopefully we will just skip spring this year and go right to summer soon. . . .
Hopefully we will just skip spring this year and go right to summer soon. . . .
April 15, 2017
Got out for a nice ride from Holland to Grand Haven - amazingly not too cold
Lake was flat.
No good performance numbers yet, got 57 GPS, but the boat was a little full . .. .
Approval from my daughter and 4 German exchange students we took for a ride:
