overpowering with I/O?

[peacekeeper6]

Is this possible? i have access to a boat with a 3.0l Merc in it, but its blown, i have a full from engine to prop 5.7L 260 setup. I was thinking of just throwing it in there. What would this cause?

 

[HT32BSX115]

Re: overpowering with I/O?

Howdy,

Well,

You didn't say what year model, size boat you're talking about.

There's usually a placard on the boat with the HID (Hull ID) number and Max weight and MAXIMUM HP allowed.

One should usually not exceed the placarded (MAX) HP rating of any boat. I think you can even run afoul of the Coast Guard if you have exceeded the recommended max HP on a boat and they bother to check.

Insurance companies may have disclaimers for that too.......IF you were to get in an accident I'll bet an insurance company would check and the injured party's Lawyer would ABSOLUTELY check! (AKA "low
hanging fruit"!!)


Now having said all that, I had an 18ft boat sold originally with as low as a 120hp 4cyl Mercruiser.... it had a placard max HP rating of 310 HP..... Which was a 409 cu-in V-8 and Mercruiser #2 drive.


Regards,

Rick

 

[tommays]

Re: overpowering with I/O?

It would depend on the boat as my 19' was sold with a 3.0 , 4.3 and 5.0

It is a 1995 boat and there is only a passanger rating nothing about HP


If you look at many new boats they will offer a 5.0 base motor and go all the way to and 8.1 for only 14,000 dollars

 

[SuperNova]

Re: overpowering with I/O?

Is this possible? i have access to a boat with a 3.0l Merc in it, but its blown, i have a full from engine to prop 5.7L 260 setup. I was thinking of just throwing it in there. What would this cause?

Lot's of bugs in the teeth due to very large smiles and high speeds...

 

[mkast]

Re: overpowering with I/O?

Define "overpowered"
125 hp Johnson on a 16 ft Starcraft.
At WOT hull didn't have any chine left for turning, so the hull felt like an aircraft barrel roll instead of a boat turning. No more turning the boat at speed.

 

[Bt Doctur]

Re: overpowering with I/O?

Guess you could PROVIDING you can build the new motor mount stringers to withstand the torque and not pull the hull up and out.

 

[Bondo]

Re: overpowering with I/O?

Ayuh,.......

Last year we pulled a Merc. 120hp./ Mod.1 drive out of a Slickcraft, SS195......
And dropped in a Merc 350Mag/ Alpha Gen.II into it.........
It's Quite a Rush,.... Pretty stable at Speed,+ it takes No Time to get there.....

 

[Flukinicehole]

Re: overpowering with I/O?

If it fits into the engine compartment put it in.

 

[96lt4c4]

Re: overpowering with I/O?

If it fits into the engine compartment put it in.

My little 305 is just asking to be pulled, so a 383 can go in.

 

[wca_tim]

Re: overpowering with I/O?

Guess you could PROVIDING you can build the new motor mount stringers to withstand the torque and not pull the hull up and out.

No disrespect intended (perhaps I'm missing something), but with a mercruiser drive, isn't the torque load borne by the transom assembly and the motor mounts and stringers predominantly support the weight of the engine keeping it properly aligned?

 

[Dakota47]

Re: overpowering with I/O?

go for it

 

[mcleaves]

Re: overpowering with I/O?

Don't you really need to know how much flex that transom can take?

I'd be concerned with hole shots with an upgrade like that if the boat wasn't initially rated for that kind of HP. That's not to say it's not rated, but this would be my biggest area of concern.

The old early 80's Bayliner Cieras came with both 4's and 8's so it's entirely plausible you are all set. You should just check so you know. If that boat was never offered with a high hp package you want to understand why and make corrections or adjust your usage.

M

 

[SuperNova]

Re: overpowering with I/O?

Don't you really need to know how much flex that transom can take?

I'd be concerned with hole shots with an upgrade like that if the boat wasn't initially rated for that kind of HP. That's not to say it's not rated, but this would be my biggest area of concern.

M

Every transom I've ever done was 3" thick plywood glassed in...didn't matter if it was an outboard, i/o.....50 h.p. to twin 454's....as long as the transom isn't rotten, and the thickness can be verified at the drainhole....overpowering shouldn't be a problem even worth considering.

 

[Bondo]

Re: overpowering with I/O?

Every transom I've ever done was 3" thick plywood glassed in...

Hmmmm,...

Mercruiser Specifies the transom Must be 2" thick.....
No more than 2, 1/8", No Less than 1, 7/8"......

But,...
I Still don't see this as an Issue to the OP......

 

[whywhyzed]

Re: overpowering with I/O?

....

 

[SuperNova]

Re: overpowering with I/O?

Hmmmm,...

Mercruiser Specifies the transom Must be 2" thick.....
No more than 2, 1/8", No Less than 1, 7/8"......

But,...
I Still don't see this as an Issue to the OP......

I'm sorry, you are right on both counts..it IS 2", my memory was faulty......and it is a non-issue anyway..
--
Stan

 

[mcleaves]

Re: overpowering with I/O?

Every transom I've ever done was 3" thick plywood glassed in...didn't matter if it was an outboard, i/o.....50 h.p. to twin 454's....as long as the transom isn't rotten, and the thickness can be verified at the drainhole....overpowering shouldn't be a problem even worth considering.

Fair enough.. I brought it up becasue I once saw a boat with a 4cyl that only had thicker glass and wood around the transom cutout. Probably ran 10-15 inches larger than the cutout all around. I also saw the same boat a year newer when I was pulling some stuff from it to put in the runner. It seemed to be thick the whole width of the boat. This one had an 8cyl. I assumed since the hulls were identical otherwise and the only difference was the engine size that the thicker glass was for the 8cyl.

But you guys see a lot more boats than I do, so maybe it was simply a change from model year to model year and nothing to do with the HP difference. Made sense at the time though

M

 

[SuperNova]

Re: overpowering with I/O?

Fair enough.. I brought it up becasue I once saw a boat with a 4cyl that only had thicker glass and wood around the transom cutout. Probably ran 10-15 inches larger than the cutout all around. I also saw the same boat a year newer when I was pulling some stuff from it to put in the runner. It seemed to be thick the whole width of the boat. This one had an 8cyl. I assumed since the hulls were identical otherwise and the only difference was the engine size that the thicker glass was for the 8cyl.

But you guys see a lot more boats than I do, so maybe it was simply a change from model year to model year and nothing to do with the HP difference. Made sense at the time though

M

Musta been Bayliners j/k. No sweat.. if you experience something different that causes you to have concern about a subject,you are more than justified to interject with your experience...thats what is really productive about forums...you get to hear from a lot of different experience and perspectives. Your input is just as valuable as anybody else's.