Proper engine size

[Bill Adkins]

I recently purchased an older glasspar 15 ft runabout from a neighbor near a local mountain lake. It came with a larger Merc 1350 which is way oversized for a 900 lb boat. What is the concinsus on proper engine sizeing for that boat, I have had many ocean based inboards but never a smaller outboard powered lake boat so I really dont have any experiance in this matter. And is a Merc a good choice for a power plant in this venue?
Bill

 

[CATransplant]

Re: Proper engine size

Does the boat have a capacity plate on it somewhere? That would be a good guide.

If not, you may be able to find the max. hp. rating over at fiberglassics.com, but you'll need the model of the boat and the year. They have the original brochures at that site, normally with horsepower ratings.

The thing about old Glaspars is that they made a lot of different models. Some were very deep-v boats, while others were more shallow. It's important to know the model to figure out the hp rating.

Depending on the age of the boat and the model, it seems a little unlikely to me that a 15' Glaspar would be rated for 135 hp.

 

[tashasdaddy]

Re: Proper engine size

the mercs, johnson/evinrude, yamaha, suzuki, honda, stay with the mainstream motor. unless you plan to maintain yourself. look around and see what dealers are near.. and go from there.

 

[hitace]

Re: Proper engine size

just check to see if its illegal to go over your max HP in your state.if its not illegal then theres nothing to worry about and if it is you can get different decal stickers.but if you are scared of going fast then it would be a good idea to down grade.

 

[CATransplant]

Re: Proper engine size

just check to see if its illegal to go over your max HP in your state.if its not illegal then theres nothing to worry about and if it is you can get different decal stickers.but if you are scared of going fast then it would be a good idea to down grade.

That's really bad advice, hitace. If his 15' Glasspar is from the 1950s, which I expect it may be, the max hp for all those models is just 60 hp. If it's actually a 15' boat, there's a good likelihood that it's from those years, although I don't have a complete list of models after the 1960s.

Advising someone to overpower a boat by 100% is just wrong. A boat rated for 60hp is dangerous with 135 hp. It's that simple. Not to mention that the transom is probably not designed for the weight or thrust of that engine.

The right thing is for him to try to tell us the model of the boat. Then we can help him find the max hp rating.

A lot of people rely on advice from this forum. Giving bad or dangerous advice to someone asking for help is just not right. It's no skin off your nose if he gets in an accident, I suppose, but the forum is here to help people with accurate, useful information.

It is neither accurate, nor useful, to recommend that someone drastically overpower a boat. You're free to do whatever you want on your boat, of course, but please don't give dangerous advice to other boaters, OK?

 

[hitace]

Re: Proper engine size

i do apologize for the bad advice.

he could reinforce the transom
and only drive in vary calm waters

 

[tashasdaddy]

Re: Proper engine size

hitace, that's the worst advice i've ever heard anybody on iboats give. this is a site to teach how to have a good running, safe boating experience. consider this when you are giving advice. it is illegal in the US to have an overpowered boat. Coast Guard regs call it and unsafe vessel. if a incident occurs, insurance does not pay off, and the injured party will own your sole, as attorneys love these cases.

 

[tashasdaddy]

Re: Proper engine size

your forgiven, just keep in mind safe boating. i have an overpowerd boat but not drastically so.

 

[Bill Adkins]

Re: Proper engine size

First of all thanks for the responses and perhaps more info was a good idea. The boat measures 15 ft from the nose to the rear of the motor well. I was told it was built 1 year before the horsepower rating was required on the data plate, perhaps 68 or 69 or the shop couldnt legally re-install the motor if it was removed.
The boat looks like the V series with a deep V configuration but it is only 15 feet long. It has the 2 seats that when slid apart form a lounge type of arrangement. The data plate does state it is 900 lbs. Thanks again for the responses.
Bill

 

[CATransplant]

Re: Proper engine size

Looking at the Glasspar brochures for 1968 and 1969, it looks like what you have is a 1969 Cutlas 15'. The weight matches yours, according to the brochure. In 1968, that was a 16' model. In 1969, the model was 15' long. The brochure doesn't give max hp specs, though. Looking at the photo, it appears that the engine is the V4 OMC engine from that year. That would make it an 85 hp or a 115 hp. I'm thinking that it's the 85, but I can't be sure from the brochure.


There was also a 15' Avalon model, but it was lighter. The Cutlass is a tri-hull design, and the Avalon is a Deep-V hull design.

The inboard/outboard version of the Cutlas came standard with a 120 hp engine. That leads me to believe that the outboard model was probably similarly rated.

So, you're probably not horribly overpowered with that 135 hp engine. Tri-hulls are notably stable and, since it came standard with the 120hp I/O, you may not be in big trouble. The fact that the company didn't list max hp. ratings should give you a pass, if you decide to keep the 135.

As you can see, once the info is available, it's pretty easy to find out the information.

However, given the age of the boat, you should have the transom thoroughly inspected for rot before opening up that outboard on it.

 

[Scaaty]

Re: Proper engine size

If its a G3, the more the better...90hp is a trolling motor..fun boats when over powered!