I realize this IS what Grady says to do.I also realize that many boats with twins were repowered without respacing the engines.Can someone say why it would be necessary to go from 28.5 inches apart to 32.5 inches?What does it accomplish and is it a good idea to put new holes so close to the old ones?2 inches either side of center certainly does not SEEM that significant.For the boats that had not been redrilled, what is the downside???What would the upside be if it was done?My boat was not redrilled, I don't have any problems with performance or handling that I'm aware of.I've been on boats driving them, since I was 14,34 years, v-hulls and catamarans.I think I would feel something was amiss if it was. :hmm Would like a real expaination before I start to obsess about what could be or not be! :bang Thanks for the help.....
why respace engines when repowering from 2 stroke to 4 strok
- Thread starter NO REGRETS
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Re: why respace engines when repowering from 2 stroke to 4 s
Traditional spacing (centerline) between V6 2 strokes was 26 inch.
With one exception and one only, all V6 4 stroke centerlines are the same so no reboring/sealing is required on repowering.
Only Yamaha F V6s were specified at 29 inches.
under no circumstance is one motor to touch the other motor, as the dimensions above provide.
Dimensions above are minimums.
Centerlines are measured from any point on one motor to the same corresponding point on another motor. The mounting holes are readily marked and bored to the dimension.
As far as going wider, limited by width of transom.
Bracket model centerlines are most times fixed and cannot be modified.
Traditional spacing (centerline) between V6 2 strokes was 26 inch.
With one exception and one only, all V6 4 stroke centerlines are the same so no reboring/sealing is required on repowering.
Only Yamaha F V6s were specified at 29 inches.
under no circumstance is one motor to touch the other motor, as the dimensions above provide.
Dimensions above are minimums.
Centerlines are measured from any point on one motor to the same corresponding point on another motor. The mounting holes are readily marked and bored to the dimension.
As far as going wider, limited by width of transom.
Bracket model centerlines are most times fixed and cannot be modified.
Re: why respace engines when repowering from 2 stroke to 4 s
Bob I measured mine at 28.5.I then went down to a marina and measured a 2007 at 32.5. Both are Bimini 306's.My question is why ? and what if you don't respace?.The difference in yamaha and suzuki weight of 225's is 3 pounds.Susuki wins on horse power and prop size but that is a different topic.I have plenty of space between them as you can see in my album so that's not part of the equation in my mind.I would like to know why Grady says to redrill for a 2 stroke to 4 stroke conversion. :hmm
Bob I measured mine at 28.5.I then went down to a marina and measured a 2007 at 32.5. Both are Bimini 306's.My question is why ? and what if you don't respace?.The difference in yamaha and suzuki weight of 225's is 3 pounds.Susuki wins on horse power and prop size but that is a different topic.I have plenty of space between them as you can see in my album so that's not part of the equation in my mind.I would like to know why Grady says to redrill for a 2 stroke to 4 stroke conversion. :hmm
Re: why respace engines when repowering from 2 stroke to 4 s
Sounds like a question for :uhm Grady engineering?
Sounds like a question for :uhm Grady engineering?
Re: why respace engines when re powerin from 2 stroke to 4 s
I'm not sure I understand the question but I can offer this.
By spacing any pair of outboards on a transom (or a bracket I guess) farther apart, you gain better slow speed handling especially around the dock. I believe this is in forward or reverse. I have not docked many twin inboard boats, but I gather they are very easy to dock thanks to the props being so far apart.
Another concern is the issue of transom height. With 25" shafts, if the outboards are too close to the center I suppose they could be too high to get 'clean' water. On deeper vee boats I suspect it would be more of a problem. I guess in theory, the farther the engines are apart the better (as long as the lower units do not drop too far below the bull). Obviously, there is a limit with walkways, transom doors, ladders, rigging, etc.
Hope this helps a little.
I'm not sure I understand the question but I can offer this.
By spacing any pair of outboards on a transom (or a bracket I guess) farther apart, you gain better slow speed handling especially around the dock. I believe this is in forward or reverse. I have not docked many twin inboard boats, but I gather they are very easy to dock thanks to the props being so far apart.
Another concern is the issue of transom height. With 25" shafts, if the outboards are too close to the center I suppose they could be too high to get 'clean' water. On deeper vee boats I suspect it would be more of a problem. I guess in theory, the farther the engines are apart the better (as long as the lower units do not drop too far below the bull). Obviously, there is a limit with walkways, transom doors, ladders, rigging, etc.
Hope this helps a little.
Re: why respace engines when repowering from 2 stroke to 4 s
In this case the motors are the same length as each other 2 stroke to 4 stroke the onle diff is the fact that they are heavier.I still can't see what 2INCHES does.I had a worldcat and they were 4 feet apart.That makes a diff. But 2 inches I don't understand..There is no performance issue with my boat at all as it's set up now.No cavatation at any speed and top speed is good with 16 inch diameter props.16x18.5x3 to be exact.43+ top speed at 5650rpm 200 gallons of fuel and two people on board.
In this case the motors are the same length as each other 2 stroke to 4 stroke the onle diff is the fact that they are heavier.I still can't see what 2INCHES does.I had a worldcat and they were 4 feet apart.That makes a diff. But 2 inches I don't understand..There is no performance issue with my boat at all as it's set up now.No cavatation at any speed and top speed is good with 16 inch diameter props.16x18.5x3 to be exact.43+ top speed at 5650rpm 200 gallons of fuel and two people on board.
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Re: why respace engines when repowering from 2 stroke to 4 s
I HAVE BEEN ON 28 GRADYS THAT GOT REPOWERD WITH 4 STROKE AND DID NOT MOVE MOTORS TO 32 1 /2 SPEC PER GRADY.THE BOATS DO NOT TRACK WELL AND THE BOW IS DOWN. I SPENT A HOLE DAY RIDING THE BOAT AND NO MATTER HOW U RUN TABS OR MOTORS DOES NOT MATER. WE R TALKING ABOUT A 28 GRADY WITH 4 STROKE YAMAHA. THE BUILDER HAS TESTED THIS BOAT WITH F225 YAMAHA AND F250 YAMAHA. AND THE RIGHT SETUP IS 32 1/2 AND # 2 BOLT HOLE. AND MOVING MOTORS APART IT DOES NOT MATTER ABOUT REDRILLING HOLES BY OTHER HOLES IF U EVER RIGGED A GRADY U NO ALL GRADY FISHING MODELS HAVE METAL SUPORT LAID UP IN THE TRANSOMS. U R TALKING ABOUT A GRADY I HAVE WORKED FOR 2 GRADY DEALERSHIPS FOR OVER 25 YEARS ALLTOGETHER AN I HAVE WORKED ON A LOT BOATS FOR THEM . THEY WOULD NEVER TELL A US TO RIG TO THAT SPEC IF IT DID NOT MATTER. ICAN TELL YOU I HAVE RIGGED ALOT OF BOATS IN 25 YEARS AND FIXED ALOT 2 AND HAVE NEVER GONE WRONG WITH A GRADY SPEC FOR RIGGING.
I HAVE BEEN ON 28 GRADYS THAT GOT REPOWERD WITH 4 STROKE AND DID NOT MOVE MOTORS TO 32 1 /2 SPEC PER GRADY.THE BOATS DO NOT TRACK WELL AND THE BOW IS DOWN. I SPENT A HOLE DAY RIDING THE BOAT AND NO MATTER HOW U RUN TABS OR MOTORS DOES NOT MATER. WE R TALKING ABOUT A 28 GRADY WITH 4 STROKE YAMAHA. THE BUILDER HAS TESTED THIS BOAT WITH F225 YAMAHA AND F250 YAMAHA. AND THE RIGHT SETUP IS 32 1/2 AND # 2 BOLT HOLE. AND MOVING MOTORS APART IT DOES NOT MATTER ABOUT REDRILLING HOLES BY OTHER HOLES IF U EVER RIGGED A GRADY U NO ALL GRADY FISHING MODELS HAVE METAL SUPORT LAID UP IN THE TRANSOMS. U R TALKING ABOUT A GRADY I HAVE WORKED FOR 2 GRADY DEALERSHIPS FOR OVER 25 YEARS ALLTOGETHER AN I HAVE WORKED ON A LOT BOATS FOR THEM . THEY WOULD NEVER TELL A US TO RIG TO THAT SPEC IF IT DID NOT MATTER. ICAN TELL YOU I HAVE RIGGED ALOT OF BOATS IN 25 YEARS AND FIXED ALOT 2 AND HAVE NEVER GONE WRONG WITH A GRADY SPEC FOR RIGGING.
Re: why respace engines when repowering from 2 stroke to 4 s
No Regrets, let me clarify.
By the way where did you take the measurements from ?
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Anyway, all twins traditionally are supposed to be mounted close to eachother to the dimensions I stated, if so, a Yamaha F (not Suzuki) on a 2 stroke repowering job requires reboring to new dimensions above. You don't have to do anything with a Suzie incl 300HP since no one would have bored less than 26 inches.
The reason for keeping them close (as possible) is what may happen on fast power-on sharp turns, the outer (turn) motor may cavitate and loose bite since the boat is pivoting on it's keel. Being closer mitigates the possibility. If spreading them out gives benefit say to improved throttle steering, then it's a trade off (as usual). As far as tracking during a white water troll, can't say if it matters, what does matter is counter rotators, in a big way.
Something else occurred when the first 33X appeared many years ago with the F225s because Yamaha was dragging their can on the F350, those small V6 motors in twins looked proportionally tiny on the transom, being further apart made them look somewhat better. The F350s on twins saved that one !
I see the Marlin at the shows with the F250s opened up a bit.
As was stated, contact Grady HQ and ask why. Report back here.
And you may need a new steering tie rod which isn't as cheap as it looks, will need it for V6 Fs anyway, not other brands of V6 4 strokes.
The 32 inch dimension may have something to do with the F350 which is a huge motor, with a huge 6 bolt bracket. Perhaps for ants-in-the-pants 4 stroke V6 guys going to V8s later?
Whenever backing down, outboards (especially bracketed and flat bottom euros) are best to tilt motor up a bit so the flow doesn't hit the transom but goes under hull.
The Suzies look perfect back there.
No Regrets, let me clarify.
By the way where did you take the measurements from ?
-------------------------------------------------------------------------------
Anyway, all twins traditionally are supposed to be mounted close to eachother to the dimensions I stated, if so, a Yamaha F (not Suzuki) on a 2 stroke repowering job requires reboring to new dimensions above. You don't have to do anything with a Suzie incl 300HP since no one would have bored less than 26 inches.
The reason for keeping them close (as possible) is what may happen on fast power-on sharp turns, the outer (turn) motor may cavitate and loose bite since the boat is pivoting on it's keel. Being closer mitigates the possibility. If spreading them out gives benefit say to improved throttle steering, then it's a trade off (as usual). As far as tracking during a white water troll, can't say if it matters, what does matter is counter rotators, in a big way.
Something else occurred when the first 33X appeared many years ago with the F225s because Yamaha was dragging their can on the F350, those small V6 motors in twins looked proportionally tiny on the transom, being further apart made them look somewhat better. The F350s on twins saved that one !
I see the Marlin at the shows with the F250s opened up a bit.
As was stated, contact Grady HQ and ask why. Report back here.
And you may need a new steering tie rod which isn't as cheap as it looks, will need it for V6 Fs anyway, not other brands of V6 4 strokes.
The 32 inch dimension may have something to do with the F350 which is a huge motor, with a huge 6 bolt bracket. Perhaps for ants-in-the-pants 4 stroke V6 guys going to V8s later?
Whenever backing down, outboards (especially bracketed and flat bottom euros) are best to tilt motor up a bit so the flow doesn't hit the transom but goes under hull.
The Suzies look perfect back there.
Re: why respace engines when repowering from 2 stroke to 4 s
I thought it was b/c the cowling was bigger so they needed to be spread out more to allow full turning.
I thought it was b/c the cowling was bigger so they needed to be spread out more to allow full turning.
Re: why respace engines when repowering from 2 stroke to 4 s
Measured the steering connection to each other.Where the tie rod connects the engines togeather in front.Mine are staying the way they are I have NO REGRETS. :goodjob
Measured the steering connection to each other.Where the tie rod connects the engines togeather in front.Mine are staying the way they are I have NO REGRETS. :goodjob
Re: why respace engines when repowering from 2 stroke to 4 s
The motors may be toed out a bit by spec on twin alignment, better to use the holes bored in transom. Good enough for your purpose.
The motors may be toed out a bit by spec on twin alignment, better to use the holes bored in transom. Good enough for your purpose.
Re: why respace engines when repowering from 2 stroke to 4 s
unclohn - that's the 29 inch dimension change for Yamaha Fs.
Note, these are twin minimums set per Yamaha for V6 Fs.
So reboring is required going from any 2 stroke V6 (26 inch) to Yamaha F V6s.
Not applicable to 4 stroker Suzie, Honda, Verado, etc.
unclohn - that's the 29 inch dimension change for Yamaha Fs.
Note, these are twin minimums set per Yamaha for V6 Fs.
So reboring is required going from any 2 stroke V6 (26 inch) to Yamaha F V6s.
Not applicable to 4 stroker Suzie, Honda, Verado, etc.