SeaCat 565 forward console - what motors to use

Rip Curl

New member
Hi,

I am looking to upgrade to 4 strokes and would like some advise on motors. The boat is SeaCat f/c 2008 model with t-top. We launch from Durban.

Currently have Yamaha 90 2 strokes at 120kg each. Looking at Suzuki 90 lean burn at 155kg. The Suzuki 70 is the same weight. Yamaha 70 is 120kg.

Would the extra 70kg make a huge difference to the handling of the boat. We normally travel 4 up.

Your advise most welcome.
 

Rory

Sealiner
the 70 yamahas are not enough to push that boat nicely i would look at 90/100/115 four strokes that hull can take them no problem they normally the same weight
 

Rip Curl

New member
Thanks rory. That was our feeling with the 70 4 strokes.

Suzuki 90 4 strokes are about 10 -20kg lighter than other makes and a couple of grand cheaper, not to mention lower on fuel consumption thanks to the lean burn technology.
 

Craig.fish

New member
Skippered a Seacat 565CC for around 2 years when they were just launched with a pair of Yamaha 60/4's. She was fine but could have done with some more power to swing her around in the surf with 4 people on board. Recently skippered a 565FC with the new Yamaha 70/4's. Awesome. Plenty low down, mid and top end. Wouldn't go more than that.

Dont overpower your boat. They become over responsive to throttle. Just find the right combo. In my opinion, the new 70's are lovely. Craig
 

Rip Curl

New member
Hi all,

Thanks for all your advise.

With regards to over powering, agree it is a waste and dangerous. The current 90 2 stroke Yamaha fitted has 66kw. The new 70 Yamaha 4 stroke has 51kw. The Suzuki 90 4 stroke has 66kw. My current motors are not over powered at all. So unless I am reading all specs wrong, the Suzuki should not be over powering the boat. My only concern is the extra 70 kg on the back with the 4 stroke Suzuki.
 

GT Mayhem

New member
Rip Curl wrote:
Hi all,

Thanks for all your advise.

With regards to over powering, agree it is a waste and dangerous. The current 90 2 stroke Yamaha fitted has 66kw. The new 70 Yamaha 4 stroke has 51kw. The Suzuki 90 4 stroke has 66kw. My current motors are not over powered at all. So unless I am reading all specs wrong, the Suzuki should not be over powering the boat. My only concern is the extra 70 kg on the back with the 4 stroke Suzuki.

And that could be it right there - power to weight ratio, have to find the right balance...

Best thing is to jump on someones boat with the F70's n see how you like them.
 

QuQ

New member
Rip Curl, I have a 565 FC with the F70's so I speak from practical experience. The trick with the F70's is that they are one of the hardest motors to prop, being uprated F60's. The std 13" alu props give plenty low down but no top end. The 14" alu props are a better compromise but flex to much at mid range (cruise). I tested several props until I tried the stainless Turbo 1 13x13.25. That was it, match made in heaven. The boat performed much better than before. It literally flies out of the hole and my revs at a 22knt cruise have dropped by 500rpm to 4500rpm. Remember these motors go up to 6300rpm. Top speed is 32knts @ 6300rpm which is plenty in my opinion.


I took a mate out onto the Knysna lagoon this past weekend. When he saw the boat on the trailer he remarked that the motors looked small on the boat. Anyway, while cruising on the lagoon at 22-24knts with him standing next to me holding the stainless rail above the windscreen, I floored the throttles. He almost landed on the motors. Moral of that little story ... plenty of mid range grunt as well!

Before buying, I considered Zuke 90's due to them being the lightest 4 stroke (155kg) in the 80-100hp range, and while I was doing all the prop testing, thought I should have got them. But now, with my boat propped as it is ... very pleased I didn't. Adding an extra 70kg on the transom will affect the balance. By how much, I don't know. But the F70's (propped correctly) are more than enough in my opinion. Maybe if you surf launch a lot and you want power in reserve, the Zuke 90's might be worth the weight penalty.
 

boatmatix

New member
70 Yamaha four strokes are the ideal motors for that boat,dont even look at anything else.
When the 565 1st came out they only had the 80hp 4 stroke Yamaha and they didnt ride as well as with the 70's.
 

QuQ

New member
Been meaning to try, but never think about it while on the water. Will try to remember this weekend and report back.
 

Fishaholic

New member
My 17 yeld 70 yammies, definitely not close to plain on one motor on sea. 14 pitch std alum props. I don't have any problem with the performance at the coast, runs good.
But up country the 70s are very pap. The same turbo props of QnQ I took 17 sec to get plain, and the got to 5400rpm only WOT, 2 person on board. An std alum 13 pitch get better plain but cavitates badly and revs out. 14 pitch I once had 4 adults and 3 children on board for cruize, couldn't get up on plain. Basically cant get it propped for use up here. OK its made for the coast, but I'm disappointed that it cant run good up here as well. My opinion I think the low down torque of the 70's not much better than the 60's. Runs 300rpm higher where it gets the 70hp from, but what about low down. Would really like to see torque curves or dyno charts between the 2.
For me the weight was also deciding factor, and the back of boat already deep when few people at back, also water gets on board through below deck fish hatch, so heavier motors would also be problem.
Just wish I could get her to run properly up here.
 

Rip Curl

New member
I have heard from more than the 2 guys in this topic of the prop size having a huge performance issue with the f70 Yamaha. This means one has to decide on out the hole pitch or top end speed.

We tend to run from Durban about 40 nautical miles and do not want power issues when coming back in a heavy swell and NE or straight into a SW wind. Hence my thoughts on the extra power of the 90 at a cost of 70kg extra weight.
 

QuQ

New member
As I say, I have the same boat and with my props I get hole shot, mid range and in my opinion, top end (32knts is plenty). I have just relocated from CT where I used to fish for Tuna at the Canyon off Cape Point - used to do over 100nm in a day. Always had plenty of power in reserve, even in a grumpy sea. That said, I would say the hull would probably handle the extra 70kg. Not sure what that would do to the balance of the boat because the balance on mine is perfect as it is. I don't think you will go wrong, either way.
 

Craig.fish

New member
Rip Curl. Chat to Grant who builds the SeaCats. He will tell you about the weight issues that may / may not arise.

Or give Ryan or Alpha at Durban Yamaha a call, who have a lot of experience with SeaCats. Yes they may be biased but Alpha in particular is a wealth of knowledge and will help you regardless as he has years of experience.

Please don't take this the wrong way, but the argument you are making your decision on doesn't make the most sense. When running in rough seas and chop, you are going to be throttling right back and extra power is going to be the least of your concerns.

Power is helpful in the surf, but the 70's are more than enough for that in my opinion.

Up to you man, but I've never heard of a boat performing better when over powered.

I'm sure Ryan can arrange a test for you on a 565 with f70's and you'll be suitably impressed
 

Craig.fish

New member
Rip Curl. Chat to Grant who builds the SeaCats. He will tell you about the weight issues that may / may not arise.

Or give Ryan or Alpha at Durban Yamaha a call, who have a lot of experience with SeaCats. Yes they may be biased but Alpha in particular is a wealth of knowledge and will help you regardless as he has years of experience.

Please don't take this the wrong way, but the argument you are making your decision on doesn't make the most sense. When running in rough seas and chop, you are going to be throttling right back and extra power is going to be the least of your concerns.

Power is helpful in the surf, but the 70's are more than enough for that in my opinion.

Up to you man, but I've never heard of a boat performing better when over powered.

I'm sure Ryan can arrange a test for you on a 565 with f70's and you'll be suitably impressed
 

QuQ

New member
Rip Curl, you are talking about spending close to R200k here. It's certainly worth your while getting on a Seacat with F70's to make sure. You can then decide for yourself.
I would be happy to give you a spin .... but I am a long way from you!
 
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