How much weight does it take?

[SeaReel]

There is a lot of discussion lately about the issue of re-powering. Many are concerned about the added weight of 4 stroke motors or re-powering with a larger or newer two stroke that is inevitebly heavier. In light of this I have a couple of questions:

Have there been any documented cases where the added weight of a new motor (four stroke or other) directly damaged a transom.

How much weight can factory transoms really handle? I know there are max hp ratings but I never see max transom loads.

On a similar issue:

After reading several posts that were concerned with engine weight I had this thought:

When does having a heavier motor diminish the performance of the boat?

I can imagine that hp and weight increase together. But at some point the relationship would reach a point of diminishing return where the added weight of the motor prevents increased performance of the boat given the boat could always handle the extra weight.

In reality would this ever happen?

Cliff

[Mist-Rest]

I'll be the first to respond with some of your question.

I spent some time with the weight issue of 4S vs 2S. Asked around in person and on a couple of boards. Bottom line was sure, a new 4S is only 150 or so more lbs than your present 2S. Now look at the water line while in your present 2S configuration then add your light weight 150# buddy to the stern. Get the picture?? Is was not good for me. In the end, while I like a lot of what the 4S brings to the market, the 2S was the only thing to hang on an older boat that was set up for a 25" shaft.

If I was starting from scratch and the boat was designed for the weight of a 4S I would do it in a heart beat. With an older hull and nothing that screams out and says "buy me"! I'll stay with what I got.

[warthog5]

This is one of the reason's that I have gone to a bracket and a large body/tub to support/offset that added weight.

[Prop Blast]

Cliff,

I think it depends on the individual hull/engine combination. With some hulls it has no affect, and others it does.

On my boat, the added weight of the F225 did not impact the floatation of my Mako or it's performance. With a half tank of gas, 2 adults and a child, T-Top and bottom paint, my hole shot is pretty darn good.

Now I did move the two group 27 batteries out from the transom area into the console -- so that had some offset.

Unforturnately, there is no way to test an engine on a boat and then swap it out if you don't like it.

Tom

[Trident]

Gents-

I sent Eddie Ring a copy of an original Mako factory specifications brochure that listed max transom weight for all the different models in the late 80's or early 90's. Obviously, this will give you a good idea as to how much weight your transom can handle. I would only use this as a guideline, because over time your boat's weight may have changed due to a rotten transom or saturated foam. And if your transom is rotten, the additional weight and increased torque from a new motor will make it fail much quicker.

When in doubt, replace the entire transom like many have done alreayd on this site. In order to compensate for the additional weight of the newer motors, you can do several things to rebalance the boat....install engine on flotation bracket, recore transom with weight saving composite material, replace all saturated foam, relocate any stern mounted batteries under the console or relocate gas tank closer to the bow.

Just some ideas.

Ed

[SeaReel]

Thanks a lot for all of the insight. Keep em' coming. I think this sight is great and really enjoy the discussion.

I ask these questions b/c eventually we will need to repower our 25 Mako. The boat resides in Texas and we have always felt our range was limited b/c of the 124 gallons she carries. Currently we have a single 200hp Johnson and have always been pleased with the performance. It is not a fast boat by todays standards but she rides really well.

Of course our first thought when the four strokes came out was that when it came time to repower we would put a 4 stroke on there and extend our range considerably and save at the pump too. I guess it is more difficult than that, especially if doing this might compromise the transom, which (knock on wood) is in considerably good shape given that the boat is 27 years old.

Cliff

[classic73mako]

Another way to look at this repowering problem for older boats (PRE 4 Stroke) is again by the weight of the motor(s) and by that I mean: Look at the manufactures orginal Max HP specifications. This is usually double the amount of the largest OUTBOARD (2 Stroke) made in that year. Find the weight for that motor and then double it. That is the Max weight that the manufacture intended on that boat's transom. Now if you want to put a 4 Stroke on the boat, it it will need to fall into that same Max weight range as outlined above. If 2 4 strokes of equal HP are going to be used, then my guess is they will be too heavy i.e. exceed the manufactures recommended weight for the year that boat was built - unless the HP of each of the 4 strokes is lowered (as is the weight) that was recommended as MAX for the 2 stroke outboards. You will need to do your own math on your specific motors and boat. However, an example of all this is from my 1973 22B - The boat's transom can take up to 270 HP Max - because the max HP made in 1973 for any manufacture of outboards was 135 hp. These motors weight in at somewhere around 220 pounds EACH so the max transom weight would be 220 x 2 = or about 440 pounds. My 1989 Yamaha 225 weighs in at 405 pounds - under the max weight for my boat's transom and under the max HP allowed on that boats transom by the manufacture.

One other point to check before you go out and spend a bunch of money on motors - if you place more HP on the transom of your boat than the boat was rated for in the year that it was built, you MAY NOT BE ABLE TO GET ANY BOATING INSURANCE TO COVER THAT BOAT.

Something to think about -

Mike

[jimcinfra]

classic73mako,

Where did you find the weight for the 1973 motor? Do you know the weight for a 70 hp for the same year?

[cranko]

I've got a 76' 25 siuted with T 130 yamaha carb, Holding 175 gal of fuel and get close to 15 gal an hour @ 30mph, thats almost 2miles a gal........... with no stress an my transom

[Jeronimo]

I look at it from a real basic approach.

Our 171 does not have aluminum knee braces bolted and glassed into the stringers like some of the new bass boats have, to which the motor is mounted. It's just a glass plywood sandwich, nothing more. We trailer it, we run it in rough water, we plow kelp, and hopefully we don't hit anything. I'd rather go on the side of caution esp. with a boat like ours that's 12 years old.

Our new 2005 115 FICHT weighs around 35#'s more than the 1996 115 Fast Strike that was on there before. A 135 Optimax weighs alot more than a 1992 135 HP motor. They just didn't build 'em anticipating hanging an extra 100 lbs. on those transoms 10 to 20 years later. That's not even getting into the 4-Strokers pandoras box.

This is all just my opinion and I really tend to be alot more on the cautious side.

Jeronimo

[classic73mako]

jimcinfra - Funny thing but in 1973 I was doing a lot of water sking behind a boat with a 135HP Evenrude on it and somewhere I remembered that the approximate weight of the motor. I think that if you try your local dealer he probably will have the weight as they have repair manuals for previous years. You may also try using the motor company web site. Another spot to try is the library - I know here in Milford, CT our library has repair manuals for all makes back for at least 10 years - but I live on the coast and boating is a way of life here for a good number of people.

Mike

[flounder]

SeaReel,

I have a 76 Model 25 with twin Johnson version (Susuki) four strokes. They weigh 410 lbs each. We do get wet feet if the bait well is full (while the fuel tanks are also full) when people are in the stern. It gets worse with a box full of tuna in addition to the bait well. However, at rest in the slip with every thing filled up the water is right at the top of the deck drain not up on the deck. To keep the feet dry, I simply use plugs in the drains while fishing under loaded conditions. I could lighten up the stern by relocating the batteries to the console and probably will this winter.

At twenty knot cruise (4,000 RPM) we get 1 1/2 NM per gal. On the troll at 1,600 to 1,900 we burn a little less than 1 gallon per hour. I've cut my fuel expense in half with these engines. The old two strokes (155 HP Evinrudes) were burning 5 to 6 gallons per hour on the troll and getting 1 NM per gallon.

[tsawyer]

Hey Flounder,

Have you tried adding scuppers? I just bought a pair, but haven't installed them yet. I've got the same boat you do, and also take on water in from the drain holes at times.

If I ever get my boat back and the scuppers installed, I'll let you know how they work.

Tom

[SeaReel]

Flounder,

Thanks for the info. How much water comes up onto the deck? So you have 820 pds on that transom? Has it ever been rebuilt? Our 1977 25 has a single Johnson 200 (two stroke)weighing in at 450 pds, and we get a little water coming up on deck when two are in the back and in the corner but never more than a cup.

I am really impressed that boat handles weight so well and it is even better with the way you are sipping fuel.

Cliff