Repowering options

[Seahaven]

I have a 4.75 Quintrex Bayhunter with a 2000 model Mercury 50hp 4-stroke.
Too little power with 3 up until I get to 5000rpm - not good for a 4-stroke I believe.
Looking to repower.
Boat is rated to 75hp so was thinking of 75hp 2 stroke Merc or maybe the same hp OptiMax. Big difference in weight though (and price) and given I don't use it every weekend, figure I can put up with a bit more noise and fuel for the lower weight and $$$$'s.
Any thoughts or problems with either of these options?

[Dan5]

Maybe have a look at the newer EFI 4's.........suzi 60....yam and merc all efi now, the 70 Suzi would be hard to beat.
The fuel injection makes a big difference........those older carby mercs were doey at best.

Dan

[Jarrah Jack]

Have a look at a Tohatsu TLDI. not the weight of a four stroke but a well regarded motor by those who have them. It depends on the servicing that available in your area as well.

[White Pointer]

I have a 4.75 Quintrex Bayhunter with a 2000 model Mercury 50hp 4-stroke.
Too little power with 3 up until I get to 5000rpm - not good for a 4-stroke I believe.
Looking to repower.
Boat is rated to 75hp so was thinking of 75hp 2 stroke Merc or maybe the same hp OptiMax. Big difference in weight though (and price) and given I don't use it every weekend, figure I can put up with a bit more noise and fuel for the lower weight and $$$$'s.
Any thoughts or problems with either of these options?

G'day,

If the boat is a good boat and you plan to keep it for a while then treat it to a good engine. The new Yamaha 4-stroke engines are very light and super efficient.

Regards,

Steve M

[wrxhoon]

I have a 4.75 Quintrex Bayhunter with a 2000 model Mercury 50hp 4-stroke.
Too little power with 3 up until I get to 5000rpm - not good for a 4-stroke I believe.
Looking to repower.
Boat is rated to 75hp so was thinking of 75hp 2 stroke Merc or maybe the same hp OptiMax. Big difference in weight though (and price) and given I don't use it every weekend, figure I can put up with a bit more noise and fuel for the lower weight and $$$$'s.
Any thoughts or problems with either of these options?


Before you spend big on a bigger donk have you thought of using a smaller pitch prop? That will fix your WOT RPM and the motor will not be under stress.

Your Merc 4 should weigh at around the 120 kg .
The 75 opti is a big engine , same as 115 hp and weighs in at around the 170kg
A 75 Merc 2 stroke will be around 140 kg , closer to your current engines weight .
If you go a Suzi 4 banger the 70 hp is about the same weight as the 75 opti .
One the lightest 75 2 strokes around would be the 70 hp Yammie at only 105 kg.
Again a 4 stroke 70 Yammie will have to be the lightest 70 4 banger at around the 120 kg but fhe is a very small engine , only 1 lt .

If I was you I wouldn't consider an old school 2 stroke , I would either go a DI 2 stroke , no smoke lots of down low torque and good fuel economy or a 4 stroke , good economy , very quiet but not as much down low power as a DI .

[Seahaven]

Thanks for the input folks.

You've swung me and I pit in the order for a 75hp DI today!

Thanks again.

;D

[Blusta]

I have owned both engines on different boats and found both to be excellent. I agree going down a size in prop for the 50 ( i had an EFI 4 stroke) could help, but for power weight and ease of operation a 70 TLDI Tohatsu may be the go. Tohatsu is 1267 cc and 143 kg and Yamaha 70 4 stroke is 120kg and 996 cc.

[Doit Vila]

Before you spend big on a bigger donk have you thought of using a smaller pitch prop? That will fix your WOT RPM and the motor will not be under stress.

Your Merc 4 should weigh at around the 120 kg .
The 75 opti is a big engine , same as 115 hp and weighs in at around the 170kg
A 75 Merc 2 stroke will be around 140 kg , closer to your current engines weight .
If you go a Suzi 4 banger the 70 hp is about the same weight as the 75 opti .
One the lightest 75 2 strokes around would be the 70 hp Yammie at only 105 kg.
Again a 4 stroke 70 Yammie will have to be the lightest 70 4 banger at around the 120 kg but fhe is a very small engine , only 1 lt .

If I was you I wouldn't consider an old school 2 stroke , I would either go a DI 2 stroke , no smoke lots of down low torque and good fuel economy or a 4 stroke , good economy , very quiet but not as much down low power as a DI .

WRX - thank you for that information. i just joined the forum with the hope of getting an answer to a similar issue.

I have a 1997 Satcer Nomad (no pod) , fitted with '97 Mercury 2 stroke 75HP and weighing in at 138kg. I also wish to upgrade to the optimax 75 but at 170khg I was concerned about the weight factor. I wish to stick with the mercury as the only marine dealer in my home town of port Vila Vanuatu is a mercury dealer.

The existing 75 hs been great - I carry up to 160 litres on board as we troll all day for Marlin. Normall 2 P.O.B plus eskies, gear, twin battereies etc etc.

Any thoughts on the weight of the optimax on a hull like the 475 Nomad - bearing in mind it is the 97 model?

Cheers and thanks

[wrxhoon]

WRX - thank you for that information. i just joined the forum with the hope of getting an answer to a similar issue.

I have a 1997 Satcer Nomad (no pod) , fitted with '97 Mercury 2 stroke 75HP and weighing in at 138kg. I also wish to upgrade to the optimax 75 but at 170khg I was concerned about the weight factor. I wish to stick with the mercury as the only marine dealer in my home town of port Vila Vanuatu is a mercury dealer.

The existing 75 hs been great - I carry up to 160 litres on board as we troll all day for Marlin. Normall 2 P.O.B plus eskies, gear, twin battereies etc etc.

Any thoughts on the weight of the optimax on a hull like the 475 Nomad - bearing in mind it is the 97 model?

Cheers and thanks


I can't give you advice on the weight issue and 75 hp I know is the max for the boat you have , most are powered by 60hp and I have seen some with 50hp.
Email Stacer and I'm sure they will advice you on the max transom weight .
Keep in mind if you repower with Optimax you will not need to carry as much fuel , around 40% less so tatal weight will be the same.

[Seahaven]

Just a quick update folks.
Took the new 75hp Opti out on Monday.
Ran it in for the required 2 hours and am won over already.
Yes it is heavier but it has been quite positive.
The steering is now more positive (maybe sitting a little lower at the stern helps) and all of the cavitation problems I had with the 50 hp 4-stroke seem to have disappeared.
I feell like a dog with 2 tails.

Bring on some good weather!

Cheers for all your advice.;D