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Author Topic:   Transom angle on 13-foot Boston Whaler

alberg35 posted 04-01-2007 01:02 PM ET (US)
The dealer who installed the new Tohatsu [30-HP four-stroke motor with power tilt and trim] has suggested transom wedges because of the "extreme" angle of the transom [of a Boston Whaler 13-foot hull] from vertical. I haven't seen anyone on this site [mention the extreme tilt of the transom on a Boston Whaler 13-foot hull]. Is [the transom angle on a Boston Whaler 13-foot hull] an actual problem or is the dealer wrong?
I'd appreciate some advice or comment before I make any changes.
footsie posted 04-01-2007 02:16 PM ET (US)
It was necessary for me to add wedges to increase the tuck under of my little Tender when using both a 8-HP four-stroke and 15-HP two-stroke Yamaha. Both of these motors have only four tilt pin holes. I got lots of "bow bounce" [without] the wedges.
Tom W Clark posted 04-01-2007 02:26 PM ET (US)
What footsie describes is the opposite of what the 13-footer suffers from, a very steep transom angle. In alberg35's case the wedges would decrease the "tuck under" of the motor, not increase it.
Most outboards have plenty of trim angle adjustment to accommodate even extreme transom angles, like that found on the 13 foot Whaler.
Old 13 footers also have laterally curved transoms which make it difficult for modern outboards to sit flat on the surface of the transom. Sometimes wedges or shims are used to make up this difference but it is an entirely different type of problem.
Binkie posted 04-01-2007 03:42 PM ET (US)
I don`t ever remember hearing any discussion of a problem with the transom angle on a 13-foot Boston Whaler on this website. There is an industry standard of about 13- to 15-degrees that all outboard boat builders and outboard manufacturers use. I believe the 13-foot Boston Whaler would be the same as any other boat. It is hard to measure accurately because of the hooked shaped bottom, and I have never seen any specs. I think what the dealer meant to say is because of the radiused transom the flat bracket doesn`t sit flush with the bracket, and some people have made wedges to eliminate the slight gap between the transom and the bracket sides, which in my opinion isn`t necessary.
Rich
alberg35 posted 04-01-2007 03:51 PM ET (US)
The dealer didn't use wedges to compensate for transom curve when he installed the motor, and while I initially was not too happy about this, he did use enough caulking/adhesive to give good contact. I agree with Binkie on that. I also tend to agree that there should be no reason to have to use wedges to decrease the vertical angle of the transom. I've never seen another 13-footer that seemed to need them, and the opinions I've seen on this board always seem to make sense.
The Tohatsu seems to be a very quiet, smooth running motor, in the little use I've had so far. I am going to have to do some weight redistribution though, to get the bow down. The motor as installed, weighs in at about 185.
Thanks to all for the comments. I'll post some "before and after" photos as soon as I figure out how to post photos to this site.
Tom W Clark posted 04-01-2007 04:48 PM ET (US)
The 13-footer's transom angle is extreme at about 20 degrees. Most outboard powered boats have transom angles of 12 to 15 degrees.
alberg35 posted 04-01-2007 08:13 PM ET (US)
Tom, does the dealers recommendation sound reasonable to you, or will I be OK without transom wedges?
Tom W Clark posted 04-01-2007 08:23 PM ET (US)
I am unclear why the dealer wants to do this. Is he afraid you will not get enough positive trim? I cannot imagine that it will not be fine the way it is.
Is there something extraordinary about the Tohatsu? Does it lack trim range?
A 13 footer does not benefit from a lot of positive trim; you cannot lift the bow significantly, nor do you want to.
Binkie posted 04-01-2007 08:32 PM ET (US)
20 degrees,I never realized that, I learn something every day. I don`t see that it matters though, just trim the motor out, or move the pin out till the motor hangs vertical.
Rich
alberg35 posted 04-01-2007 11:39 PM ET (US)
I was a little puzzled myself when the dealer suggested transom wedges. the boat has power T&T and seems to have a complete range of trim available by that means. I sure don't want to trim bow up, since the increased weight of the new engine already tends to do that. As far as I know, the trim geometry of the Tohatsu is about identical to Nissan and probably Mercury.
If I seem a bit dumb on this subject, I'll admit to being mostly a sailing guy who hasn't owned a planing outboard and motor since the old runabout and Evinrude 15 I had as a teenager, a LONG time ago. I'm more inclined to go with the collective wisdom of this board than with the dealer.
Thanks
Ken Jacobsen
vandenbg posted 04-03-2007 02:54 PM ET (US)
I inatalled a 30 Tohatsu & used wedges.
OK Whaler
John from Madison CT posted 04-07-2007 09:32 PM ET (US)
I find it amazing the crap you hear out of the mouths of many boat dealers.
boatboy posted 05-15-2007 01:31 PM ET (US)
My 1968 Boston Whaler 13-footer came with a 25-HP outboard. I notice the motor was clamped to the transom OK without any wedges, but the motor trim pin was all the way out, away from transom. The boat had a good ride--still could go another notch out but there weren't anymore. I put a small wedge between the motor and boat and that helped the bow ride a small amount higher which was better but it took longer to get onto [plane] with two men. For some reason these 13-foot boats need the 20-degree transom angle. I since put a 50-HP motor with power trim, and, if I tuck the motor in starting out and as the boat picks up speed I will be triming out all is well, boat rides great, but you can get the bow too high very easy and need to be careful.
Martman posted 05-16-2007 02:54 PM ET (US)
I had a buddie use wedges (upside down) to get the motor to trim up enough to get the prop out of the water when at the boat slip.

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Author	Topic: Transom angle on 13-foot Boston Whaler
alberg35	posted 04-01-2007 01:02 PM ET (US) The dealer who installed the new Tohatsu [30-HP four-stroke motor with power tilt and trim] has suggested transom wedges because of the "extreme" angle of the transom [of a Boston Whaler 13-foot hull] from vertical. I haven't seen anyone on this site [mention the extreme tilt of the transom on a Boston Whaler 13-foot hull]. Is [the transom angle on a Boston Whaler 13-foot hull] an actual problem or is the dealer wrong? I'd appreciate some advice or comment before I make any changes.
footsie	posted 04-01-2007 02:16 PM ET (US) It was necessary for me to add wedges to increase the tuck under of my little Tender when using both a 8-HP four-stroke and 15-HP two-stroke Yamaha. Both of these motors have only four tilt pin holes. I got lots of "bow bounce" [without] the wedges.
Tom W Clark	posted 04-01-2007 02:26 PM ET (US) What footsie describes is the opposite of what the 13-footer suffers from, a very steep transom angle. In alberg35's case the wedges would decrease the "tuck under" of the motor, not increase it. Most outboards have plenty of trim angle adjustment to accommodate even extreme transom angles, like that found on the 13 foot Whaler. Old 13 footers also have laterally curved transoms which make it difficult for modern outboards to sit flat on the surface of the transom. Sometimes wedges or shims are used to make up this difference but it is an entirely different type of problem.
Binkie	posted 04-01-2007 03:42 PM ET (US) I don`t ever remember hearing any discussion of a problem with the transom angle on a 13-foot Boston Whaler on this website. There is an industry standard of about 13- to 15-degrees that all outboard boat builders and outboard manufacturers use. I believe the 13-foot Boston Whaler would be the same as any other boat. It is hard to measure accurately because of the hooked shaped bottom, and I have never seen any specs. I think what the dealer meant to say is because of the radiused transom the flat bracket doesn`t sit flush with the bracket, and some people have made wedges to eliminate the slight gap between the transom and the bracket sides, which in my opinion isn`t necessary. Rich
alberg35	posted 04-01-2007 03:51 PM ET (US) The dealer didn't use wedges to compensate for transom curve when he installed the motor, and while I initially was not too happy about this, he did use enough caulking/adhesive to give good contact. I agree with Binkie on that. I also tend to agree that there should be no reason to have to use wedges to decrease the vertical angle of the transom. I've never seen another 13-footer that seemed to need them, and the opinions I've seen on this board always seem to make sense. The Tohatsu seems to be a very quiet, smooth running motor, in the little use I've had so far. I am going to have to do some weight redistribution though, to get the bow down. The motor as installed, weighs in at about 185. Thanks to all for the comments. I'll post some "before and after" photos as soon as I figure out how to post photos to this site.
Tom W Clark	posted 04-01-2007 04:48 PM ET (US) The 13-footer's transom angle is extreme at about 20 degrees. Most outboard powered boats have transom angles of 12 to 15 degrees.
alberg35	posted 04-01-2007 08:13 PM ET (US) Tom, does the dealers recommendation sound reasonable to you, or will I be OK without transom wedges?
Tom W Clark	posted 04-01-2007 08:23 PM ET (US) I am unclear why the dealer wants to do this. Is he afraid you will not get enough positive trim? I cannot imagine that it will not be fine the way it is. Is there something extraordinary about the Tohatsu? Does it lack trim range? A 13 footer does not benefit from a lot of positive trim; you cannot lift the bow significantly, nor do you want to.
Binkie	posted 04-01-2007 08:32 PM ET (US) 20 degrees,I never realized that, I learn something every day. I don`t see that it matters though, just trim the motor out, or move the pin out till the motor hangs vertical. Rich
alberg35	posted 04-01-2007 11:39 PM ET (US) I was a little puzzled myself when the dealer suggested transom wedges. the boat has power T&T and seems to have a complete range of trim available by that means. I sure don't want to trim bow up, since the increased weight of the new engine already tends to do that. As far as I know, the trim geometry of the Tohatsu is about identical to Nissan and probably Mercury. If I seem a bit dumb on this subject, I'll admit to being mostly a sailing guy who hasn't owned a planing outboard and motor since the old runabout and Evinrude 15 I had as a teenager, a LONG time ago. I'm more inclined to go with the collective wisdom of this board than with the dealer. Thanks Ken Jacobsen
vandenbg	posted 04-03-2007 02:54 PM ET (US) I inatalled a 30 Tohatsu & used wedges. OK Whaler
John from Madison CT	posted 04-07-2007 09:32 PM ET (US) I find it amazing the crap you hear out of the mouths of many boat dealers.
boatboy	posted 05-15-2007 01:31 PM ET (US) My 1968 Boston Whaler 13-footer came with a 25-HP outboard. I notice the motor was clamped to the transom OK without any wedges, but the motor trim pin was all the way out, away from transom. The boat had a good ride--still could go another notch out but there weren't anymore. I put a small wedge between the motor and boat and that helped the bow ride a small amount higher which was better but it took longer to get onto [plane] with two men. For some reason these 13-foot boats need the 20-degree transom angle. I since put a 50-HP motor with power trim, and, if I tuck the motor in starting out and as the boat picks up speed I will be triming out all is well, boat rides great, but you can get the bow too high very easy and need to be careful.
Martman	posted 05-16-2007 02:54 PM ET (US) I had a buddie use wedges (upside down) to get the motor to trim up enough to get the prop out of the water when at the boat slip.