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Author Topic:   Mounting new motor on old Boston Whaler

Shadow posted 07-01-2003 04:33 PM ET (US)
I have a 1969 16/17 foot hull. I'm in the process of fixing it up and plan to buy a new Mercury 60 hp, 4 stroke engine. What is the best way to mount the engine. The local dealer I plan to buy the motor from does not sell Boston Whalers, so is not familiar with the lower bolts that hold the motor that are blind lag bolts, which will be below the water line, I think. Any help and advise would be greatly appreciated. Shadow
Bigshot posted 07-02-2003 11:28 AM ET (US)
Raise the engine about 1.5" above the transome and that makes bolt access easy.
Draftmanswife posted 07-03-2003 10:55 AM ET (US)
I did that on my new Yamaha, Big, and it worked great on my 73, 13...
Janis
JohnJ80 posted 07-03-2003 11:01 PM ET (US)
most non whaler dealers that i have seen don't handle the hidden bolts well.
make sure the bolts are siliconed on the outside (Si, not 5200 adhesive) to make sure there isn't any water working its way in. Mine came without the Si in them, and it was bone dry but being liberal with Silicon is usually not a bad thing on boats.
Make sure the cover plate is cleaned off from all the old gunk then, again VERY LIBERALLY apply more Silicon around the edges of the opening where the plate will seat. Shot an extra shot down the screw holes.
Then assuming the bolts are tight, carefully place the plate back in place and seat it well in the goo. Screw it down tight. You should have no problem getting it water tight.
Assuming this dealer all all non whaler dealers will mount the motor too low. Whaler recommends 0-3/4" for the AV plate above the bottom of the boat. Common wisdom on this forum and my experience is that about 1.5" above the hull bottom is much better (although I don't have any experience with your hull - call whaler) At any rate, you may need to experiment. Motor placement has a big effect on performance and ride - like one hole can cause or remove porpoising. The ride can go from hard to soft etc... However, provided you are not in really rough water (open ocean etc...) you can probably safely be ok with being over the 3/4" whaler recommendation. 3/4" was still too low (V shaped 4' rooster tails off the lower unit) on my dauntless 15 even though that met Whaler's max height.
Next thing is that since your hull is older it was probably designed for a lighter motor. 4 strokes are weights that boat designers back then didn't even dream about. If so, this can cause performance issues like porpoising, poor hole shot etc... If this is the case, you should consider adding a fin. My favorite is the Grand Island Marine Turbo Lift, but I don't know if they have one for that low of horse power. Call them and find out. A fin will take care of most of the porpoising etc..
Next thing after that would be props, and that is another whole discussion. There are others here that have a ton more experience in that than I, but this can also solve alot of problems that may remain.
Shadow posted 07-04-2003 06:22 AM ET (US)
Thanks Johnj80 for the detailed reply. I now have an idea why you raise the motor. Now the next question would have to be "What Prop for the 60hp 4 stroke pushing a 1969 16/17 BW?" I'll be useing this Whaler as a fishing boat and slow trolling in Rartan Bay, NJ, On calm days I'll go around Sandy Hook. Shadow
whalernut posted 07-04-2003 09:16 AM ET (US)
Yuo should have no weight problems with that engine, I think they weigh in at around 250 pounds, my `73 16` Currituck has a 1975 85h.p. Johnson that weighs more than that and is fine, but I wouldn`t go over 300 pounds on that hull. Jack.
Shadow posted 07-04-2003 11:47 AM ET (US)
According to the catolog the dry weight for Merc 60hp 4 stroke is 248 lbs. I guess I should go to the performance forum to find out what the best prop would be for that set up. Thanks for all the input. Shadow.

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Author	Topic: Mounting new motor on old Boston Whaler
Shadow	posted 07-01-2003 04:33 PM ET (US) I have a 1969 16/17 foot hull. I'm in the process of fixing it up and plan to buy a new Mercury 60 hp, 4 stroke engine. What is the best way to mount the engine. The local dealer I plan to buy the motor from does not sell Boston Whalers, so is not familiar with the lower bolts that hold the motor that are blind lag bolts, which will be below the water line, I think. Any help and advise would be greatly appreciated. Shadow
Bigshot	posted 07-02-2003 11:28 AM ET (US) Raise the engine about 1.5" above the transome and that makes bolt access easy.
Draftmanswife	posted 07-03-2003 10:55 AM ET (US) I did that on my new Yamaha, Big, and it worked great on my 73, 13... Janis
JohnJ80	posted 07-03-2003 11:01 PM ET (US) most non whaler dealers that i have seen don't handle the hidden bolts well. make sure the bolts are siliconed on the outside (Si, not 5200 adhesive) to make sure there isn't any water working its way in. Mine came without the Si in them, and it was bone dry but being liberal with Silicon is usually not a bad thing on boats. Make sure the cover plate is cleaned off from all the old gunk then, again VERY LIBERALLY apply more Silicon around the edges of the opening where the plate will seat. Shot an extra shot down the screw holes. Then assuming the bolts are tight, carefully place the plate back in place and seat it well in the goo. Screw it down tight. You should have no problem getting it water tight. Assuming this dealer all all non whaler dealers will mount the motor too low. Whaler recommends 0-3/4" for the AV plate above the bottom of the boat. Common wisdom on this forum and my experience is that about 1.5" above the hull bottom is much better (although I don't have any experience with your hull - call whaler) At any rate, you may need to experiment. Motor placement has a big effect on performance and ride - like one hole can cause or remove porpoising. The ride can go from hard to soft etc... However, provided you are not in really rough water (open ocean etc...) you can probably safely be ok with being over the 3/4" whaler recommendation. 3/4" was still too low (V shaped 4' rooster tails off the lower unit) on my dauntless 15 even though that met Whaler's max height. Next thing is that since your hull is older it was probably designed for a lighter motor. 4 strokes are weights that boat designers back then didn't even dream about. If so, this can cause performance issues like porpoising, poor hole shot etc... If this is the case, you should consider adding a fin. My favorite is the Grand Island Marine Turbo Lift, but I don't know if they have one for that low of horse power. Call them and find out. A fin will take care of most of the porpoising etc.. Next thing after that would be props, and that is another whole discussion. There are others here that have a ton more experience in that than I, but this can also solve alot of problems that may remain.
Shadow	posted 07-04-2003 06:22 AM ET (US) Thanks Johnj80 for the detailed reply. I now have an idea why you raise the motor. Now the next question would have to be "What Prop for the 60hp 4 stroke pushing a 1969 16/17 BW?" I'll be useing this Whaler as a fishing boat and slow trolling in Rartan Bay, NJ, On calm days I'll go around Sandy Hook. Shadow
whalernut	posted 07-04-2003 09:16 AM ET (US) Yuo should have no weight problems with that engine, I think they weigh in at around 250 pounds, my `73 16` Currituck has a 1975 85h.p. Johnson that weighs more than that and is fine, but I wouldn`t go over 300 pounds on that hull. Jack.
Shadow	posted 07-04-2003 11:47 AM ET (US) According to the catolog the dry weight for Merc 60hp 4 stroke is 248 lbs. I guess I should go to the performance forum to find out what the best prop would be for that set up. Thanks for all the input. Shadow.