Horsepower - Old V's New

[tryhard]

G'day raiders,

I have a question relating to the difference in horsepower ratings between old engines and newer engines.

A bit of background 1st:-

I have a Quintrex Cruiseabout powered by a Suzi 85 ( DT85) mid 80's

Motor has been solid with major issues including Flat batteries & dirty fuel !

The max hp rating on the hull compliance plate is 85 hp

The RPM at WOT is 5100 according to the taco but I have a feeling that its not as quick as my previous cruiseabout that had a blueband 80 hp Merc. (used to do about 45 MPH at about 5500 rpm)

I am considering the upgrading the motor but will not consider new as the motor would be worth more than the boat and there would be no likelihood of ever recovering the value if sold.

The options are either rebuild or replace with later model. (or do nothing at all!)

I recall having a discussion with Hueys dad many years ago & my recollection of his comment was something like this: -

"Older motors had hp rated at the fly wheel - newer motors are rated at the prop. Newer motors of the same horsepower are therefore more powerful than the older equivalent"

So what would be a mid 90's to early 2000's equivalent to the 85 Suzi ? (and where can I get one for $10 !?!??)

any thoughts on this ?

[chrisg]

Tryhard

The hp change happened around the 80's I think...but not at the same time. Some makers were at one point selling motors using both methods. Your mid 80's Suzy falls right in there and you have to do some research in to the exact build date to be sure.

5100 rpm is a little low for WOT...you really want to be hitting 5500 I would say. Whilst de-propping would reduce your top speed a tad you would find the motor would feel sharper and more lively.

Don't get too caught up in other boats speed and performance..subtle differences in hulls, motor height etc can have big differences in the outcome. You can't really compare that closely.

If the motors solid and does everything that you need save your pennies...its costing you nothing.

I would look to a replacing the whole package when money allows. Thats easy to say isn't it!

Chris

[Flightmanager]

On the other hand , if you like the hull , and it is not on its last legs , why not repower ? I did this to my 1976 hull , and I save money every time I take it out. The new engine uses half the fuel that the old one did , and has more power !! A typical days boating now costs me about $25.00 , at todays fuel prices , with the old engine , the same distance would cost me over $50. I would do this about 40 times a year , 40 X $25.00 =$1000 ! Thats just the monetary side , I now have more reliability , less noise and less smoke etc .

Just an option to consider !

Ross

[seagull64]

G'day raiders,

I have a question relating to the difference in horsepower ratings between old engines and newer engines.

A bit of background 1st:-

I have a Quintrex Cruiseabout powered by a Suzi 85 ( DT85) mid 80's

Motor has been solid with major issues including Flat batteries & dirty fuel !

The max hp rating on the hull compliance plate is 85 hp

The RPM at WOT is 5100 according to the taco but I have a feeling that its not as quick as my previous cruiseabout that had a blueband 80 hp Merc. (used to do about 45 MPH at about 5500 rpm)

I am considering the upgrading the motor but will not consider new as the motor would be worth more than the boat and there would be no likelihood of ever recovering the value if sold.

The options are either rebuild or replace with later model. (or do nothing at all!)

I recall having a discussion with Hueys dad many years ago & my recollection of his comment was something like this: -

"Older motors had hp rated at the fly wheel - newer motors are rated at the prop. Newer motors of the same horsepower are therefore more powerful than the older equivalent"

So what would be a mid 90's to early 2000's equivalent to the 85 Suzi ? (and where can I get one for $10 !?!??)

any thoughts on this ?

Hi tryhard,

i was in a similar situation not long ago. i have a 4 mt quintrex which had a 1979 model 25 hp johnson, ample for the boat. i was looking at upgrading to a 40 hp as the kids are a bit bigger and a bit of extra push was needed ( nothing wrong with the johno at all ). max rated hp is 40. knowing that the new motors are prop rated and my old was flywheel rated i opted for a 30 hp. to be on the safe side.

my question to you is, do you disconnect your battery(s) when being idle at home ? i disconnect mine at the end of every flush, i havnt needed to charge it for at least 4 years and i give it a turn over at least every two months

secondly how long do you keep your fuel in between uses as stale fuel will give you starting problems, fouls plugs and hence drains your battery.

Im not sure how you could go about this, but maybe you might have to strengthen the transom in order to upgrade but id say if the motor you have now is serving you well otherwise, id stick with it, disconnect the battery when not in use and toss old fuel..

hope this has helped in some way

cheers

Bill

[tryhard]

Seagull,

I try to never keep fuel for too long, I generally drain the main tank after each use unless I know I'll be using it again in the near future. (I put any excess in the car)

The fuel problems related to there being crud in the tank from a previous owner - had to pull the fuel guage sender unit out and clean the tank - there were chunks (silicon) in the tank !

I have now put in an inline filter before the primer bulb - that became buggered due to the silicon jamming up the one way valves as well.

I replaced my failed battery and I always take my battery out not only to keep it charged up but also I like to remove anything that might be attractive to those who might feel that their need is greater than mine!

I now also take the spare battery fom the car to be on the safe side - theres nothing more embarassing than being towed back to the ramp for problems that you should have been prepared for in the 1st place !

The point I was making was that I have not had any insurmountable problems with the motor - as Tim the Toolman says - I want "More Power!!"

Its important to spend more time fishing & less time getting there - nah, not really - but I am thinking longer term reliability, better fuel economy & maybe a bit less noise.

thanks for your reply

[Chris 55]

The fuel problems related to there being crud in the tank from a previous owner - had to pull the fuel guage sender unit out and clean the tank - there were chunks (silicon) in the tank !

I have now put in an inline filter before the primer bulb - that became buggered due to the silicon jamming up the one way valves as well

Tryhard it sux to find problems like this that others have left

This is a good thing to look for when buying an older model boat

Please note that silicon should never be used near petrol as it turns to gel and will block any valve, jet or passage it comes in contact with this will usually require the carbies to be cleaned out and have compressed air blown through it

If your boat has an inbuilt fuel tank a good quality fuel filter is a must I feel and a basic inline filter a minimum

Hope you get it all sorted out

Repowering with a late model 2nd hand motor is the best way to go if the hull is solid, unless you find another boat you like that has a late motor fitted and is a better proposition when you weigh up the price and fit out to what you already have

You have to remember that the value of the hull is minimal in the price of a 2nd hand boat so by upgrading the motor you will increase the value of the boat

Sorro has repowered his boat this year with a 2nd hand 115 Evilrude from Huey and it is way better on fuel not to mention nice and quiet (no Ross it's not an Etec)

Huey should be back from his break soon and can give you some ideas and figures to work with

Chris

[tryhard]

Tryhard it sux to find problems like this that others have left

This is a good thing to look for when buying an older model boat

Please note that silicon should never be used near petrol as it turns to gel and will block any valve, jet or passage it comes in contact with this will usually require the carbies to be cleaned out and have compressed air blown through it

If your boat has an inbuilt fuel tank a good quality fuel filter is a must I feel and a basic inline filter a minimum

Chris,

fortunately (unfortunately) the silicone seemed to be gasket silicone and I had a lovely mix of long strings about 40mm long and little balls about 4mm in diameter - the strings happily went through the pick up but the little balls were the perfect size to clog the two holes in the brass pick up fitting.

the upshot being that the stringy bits didnt even get to the filter /seperator the just lodged in the priming bulb - I had to clear this on the water (carry a spare) but then I found I couldnt pump juice through when I got it home - progressive diagnosis found that the bloody silicone balls were neatly jambed into both pick holes!!!!

Aaah the joys of boat ownership - least it fills in all that spare time

[Chris 55]

yeah who needs a garden when you have a boat

Chris

[macka17]

Hi.

I have a Stacer 5.25 Bowrider'02 model. Came with a Merc. Carby. 75hp. Same year. 64hrs on computer reading.

I wanted a bit more h.power for towing grandkids, without going overboard.

I went to a 90hp Merc Optimax.

15 hp on paper. 50% on water. and no comparison with fuel. 90 Opti uses about 60% of 75ph fuel. On same trips. Long and short.

Trolling. I don't even neeed a fuel tank.

90 Opti will give you more power than old 85's by a fair margin. With a fraction of fuel consumption.

If boat still good for a long while yet. Providing Transom weight ok. That's the way I'd go.

Otherwise a new carby motor.. Cheaper. and lighter. Plus noisier and thirsty..

Think about getting a pod welded on back of boat. Not too exxy. All bonuses. Longer waterline. Rear step. Carry more weight. Plane easier. Full transom. Safer..

There's one up here.. Great older boat....

Second hand motors..

Why buy somebody elses problems.. WHY was it sold..........I don't think the old Suzy's have spare part supplies anymore ???. Similar to the Chryslers. Could be wrong there though.

But, at 22yrs old. Going out to sea. New motor in my eyes.

Quinnie will last forever anyway. and for coastal fishing in that size. There's not many really much better Tinnies around. Without going to the Fishers etc. (Zillions of $$$$$$$$$$$$$ too)

I'd get a good service/check up on thet donk. while saving for a new motor. Give peace of mind at least.

Regards

Macka17

[a boat]

Hi Mate, when the Japanese engines started to take off here in the mid 1980s is when things changed. The old timers like Evinrude/Johnson and Mercury used to rate Hp at flywheel but that chaged around the time your engine was new. Any engine of mid 1990s or newer will be prop rated and a 70HP Johnson/Evinrude or Yamaha would perform about as good as your 85HP Suzuki with a 75HP Mercury easily outperforming it due to being a bigger cubic capacity engine and the fact that it is the same as the 90HP Mercury.

I would search for any of these engines and you would be looking at around $4-$5K for such a thing.

At the moment I have a new old stock 75HP Mercury that we are prepared to let go at below cost so that may interst you becasue it is brand new with 3 year warranty and may not be over capitilising your boat.

If you choose to keep your engine get a smaller pitched prop to allow the engine to reach a better WOT RPM of 5500 with a normal load. As for rebuilding it, not much point because 2-Strokes do not physically ware out. I would do some preventative maintance like head gasket and water pump once the engine has been a good check over and there is no bad signs of corrosion and it should last you many more years. The biggest problem with older Jap engines is corrosion and in fact your engine will have anodes internally that need to be replaced so that the engine does not corrode from inside out.

If you like plan on using the boat up this way and swing by and I can give you my thoughts on the best thing to do.

Cheers,

Huey.

[tryhard]

Hi.

Think about getting a pod welded on back of boat. Not too exxy. All bonuses. Longer waterline. Rear step. Carry more weight. Plane easier. Full transom. Safer..

There's one up here.. Great older boat....

Second hand motors..

Why buy somebody elses problems.. WHY was it sold..........I don't think the old Suzy's have spare part supplies anymore ???. Similar to the Chryslers. Could be wrong there though.

But, at 22yrs old. Going out to sea. New motor in my eyes.

Macka,

thanks for your input, I'd love to put a 90 on the back - I've seen the same boat with 115 But I reckon thats seriously over powered !

As for the pod - well, I planted a money tree in the garden, but it died !!!

Did I understand that you have seen a cruise about with a pod ? - if so I'd be interested to see a photo if you can get one - I cant visualise what that would look like.

I have not yet had a parts problem apart from not being able to get a replacement decal for the cowling.

I think that a new motor does not make economic sense for me as I would never recover the (depreciated) cost particularly if I wanted to sell in 12 months or so.

Anyways all food for thought.

[tryhard]

At the moment I have a new old stock 75HP Mercury that we are prepared to let go at below cost so that may interst you becasue it is brand new with 3 year warranty and may not be over capitilising your boat.

If you choose to keep your engine get a smaller pitched prop to allow the engine to reach a better WOT RPM of 5500 with a normal load. As for rebuilding it, not much point because 2-Strokes do not physically ware out. I would do some preventative maintance like head gasket and water pump once the engine has been a good check over and there is no bad signs of corrosion and it should last you many more years. The biggest problem with older Jap engines is corrosion and in fact your engine will have anodes internally that need to be replaced so that the engine does not corrode from inside out.

If you like plan on using the boat up this way and swing by and I can give you my thoughts on the best thing to do.

Cheers,

Huey.

Huey,

I'll be up there with my $10.00 tomorrow !!!!!

the budget does not permit serious expenditure at the moment but your responses confirm the patterns that I am seeing not only here but in other conversations I've had as well.

Interesting point you make on the anodes - this is something I did not know - will definately look into this.

thanks for the offer to look at it - I should pop in if I get a chance I haven't been up your way for years.