Compliance plate

[Lucky Drifter]

Happy new year everyone. Can anyone help please we are looking to buy a new Yamaha T60 hp high thrust outboard & we need to make sure that our 2002 26X complies for that size engine. Does anyone know where to find a manufacturers compliance plate. Thanks Len

[kmclemore]

I don't know that they came with a compliance plate. Mine doesn't have one. They DO have a safety decal, and a copy of that is available on this website.

[Lucky Drifter]

Thanks knclmore I think I have found what I need. On page 20 of the original owners instruction manual under powering.
" The boat is designed for an outboard motor of no more than 50 horsepower. Do not use a larger engine. "
Looks like we will get a 50 hp or we could invalidate our insurance.
Regards Len

[NiceAft]

Lucky Drifter,

Don’t be concerned about having to get a 50 as opposed to a 60; there is no appreciable difference in that 10hp. Now if you wanted a 90, well that’s a difference

[Russ]

I'm not sure what regulations and policies your insurance has. There are many (like me) with 70hp motors and my insurance has no problem. That may be because BWY was authorized by Macgregor to install 70hp motors. I don't believe there was ever a proper compliance plate as some boats have.

When in doubt, the 50 would be the safest bet. As Ray mentioned. the difference in HP is probably negligible.

[Be Free]

Our boats did not come with "compliance plates". It is my understanding that the HP recommendation in the manual was based more on the weight of the engine and the ability to remove it for service without needing a hoist. A modern 70 weights about what a 50 weighed when that manual was written.

[kmclemore]

A modern 70 weights about what a 50 weighed when that manual was written.

There’s certainly enough experiential evidence that a 70 works on a Mac transom, but regarding weight and suitability I would note that weight is only one factor in the decision on motor size.

The dynamic forces exerted upon the transom by a 50 vs 70 hp motor are quite different, keeping in mind that those forces need to be evaluated under all motoring conditions (weather, turn angle, trim, wave buffeting, etc.) in order to determine suitability and safety. The factory conducted that analysis for a 50, but to my knowledge never did for anything larger.

[Lucky Drifter]

Thanks everyone
To make sure for insurance I think we will get a 50hp
Best regards Len

[Be Free]

A modern 70 weights about what a 50 weighed when that manual was written.

There’s certainly enough experiential evidence that a 70 works on a Mac transom, but regarding weight and suitability I would note that weight is only one factor in the decision on motor size.

The dynamic forces exerted upon the transom by a 50 vs 70 hp motor are quite different, keeping in mind that those forces need to be evaluated under all motoring conditions (weather, turn angle, trim, wave buffeting, etc.) in order to determine suitability and safety. The factory conducted that analysis for a 50, but to my knowledge never did for anything larger.

You'll get no argument from me re: the forces exerted by the differing engines. There is no doubt that the 70 is working the entire boat, not just the transom, harder than a 50 would. Do you know that there was any actual analysis of the forces exerted by that or any other engine? You've been doing this longer than I have so you may have seen or heard something that I have not. I've been under the impression that most of the engineering was more empirical than theoretical. I'm not saying it's a bad way of doing it, I'm just asking.

[Russ]

Thanks everyone
To make sure for insurance I think we will get a 50hp
Best regards Len

That would be the prudent choice.

[NiceAft]

My 50 HP Honda four stroke (original power on my 2005 ) pushes Nice Aft up to about 10 knots when fully loaded, and about 17 knots when empty & with empty ballast. I can cruise along at 7 knots quite efficiently on lakes, rivers, & back bays, not the ocean.

[kmclemore]

And mine, with an old Nissan 50 nail, manages 20+ mph on the water with the two of us and lightly loaded.

[Highlander]

I believe a boat over 25ft doe,s not require a compliance plate ! check ur Fed. gov. coast guard regs , that,s why mac,26 do not have one , also the only reason Roger recommended a 50 hp eng was because it was the largest engine that can still be pull started ! , if ur battery went dead , which is really redundant these days with the mini battery boosters avail no bigger than a pac of cigs ;
My Merc 75hp 4 stroke "big block" weighs in around #400 I,m sure with no issues . I did add re-enforcement plates in the motor well & lower inside transom
J

[Be Free]

Highlander, you are 100% correct on the Coast Guard regulations. The OP (Lucky Drifter) is in Australia. Their regulations may have required one when it was imported.

[OverEasy]

Hi Lucky Drifter!

Congrats on looking for a New Engine for the New Year!

Everybody’s right (so far….. )

When we were considering getting a new engine we went the long way around checking all the boxes to make sure that we didn’t bollix it up and violate the regulations or insurance or our vessel.

There is the specific horse power limitation specified in the original owners manual from MacGregor.
The local US Coast Guard explained that this would have been done by both calculation and by demonstration that would have taken into account the thrust loading, vessel structural aspects and personnel/equipment loading.

> The calculation aspect would have been what is termed ‘hand calculations’ in that there wasn’t an FEA (Finite Element Analysis) requirement for the manufacturer to comply with. Nothing wrong with hand calculations (we went to the moon with people on board based upon hand calculations (yes there were computational aspect made with computers but it wasn’t anything like FEA as we know it today…it just wasn’t available except in the most crude rudimentary form and no one had any confidence in it as it hadn’t been proven out to be anywhere near as accurate as hand calculations). The calculations for vessels were/are generally very conservative as to take into account manufacturing and material characteristics and potential degradation aspects that can be anticipated. The regulations at the time would have required someone with a Professional Engineering certification to have reviewed and approved those calculations as would have the manufacturer’s liability insurance company which is a standard aspect. All that said the calculation aspect would have been on the conservative side to ensure the approvals meaning there would be some excess capability in the design.

> The demonstration aspect typically is just that, a demonstration of the vessel with the particular equipment and conditions within which the vessel is going to be operated at…. Empty and loaded. Typically there are general deflection aspects measured to determine structural rigidity to handle the engine weight statically and while producing thrust statically and while underway. Typically this would have been limited by practicality to the transom area looking for deflections from side-to-side and vertically. The general aspect would be to be avoiding excessive deflections which would indicate excessive strain. That’s not to say it doesn’t move at all, but that what movement does occur is slight and within the anticipated material / design characteristics (as determined from the hand calculations). This semi feedback loop tends to validate the calculations and vice-versa.

> There are also aspects of certification that defer to manufacturer’s documentation recommendations in lieu of a compliance data plate.
The regulating governmental body for your area generally has discretion in this aspect as the regulating authority. They may consider that newer lighter engines of a marginally higher potential horse power are/are-not acceptable. The same goes for the applicable insurance under writer. Best to ask ahead of time as an inquiry as they both are going to determine whether your set up is acceptable for use and insurance.

> In our case we wanted to have a more durable robust lower end on our new engine and the Suzuki DF60AV series engines provided that. Our use of a 60 hp version was considered a marginal increase in power, a draw on weight and acceptable. This was confirmed by our insurance carrier. We also added an additional load spreader plate of 3/4 inch thick G-10 friberglass to the transom to help stiffen it and distribute any additional dynamic loading over a larger area to provide additional margin.





Again, Congratulations!
Hope this helps.

Best Regards,
Over Easy