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Old 28 July 2008, 04:18   #1
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Searider engine options

Morning Chaps,

What an amazing weekend weather wise! - the solent was like a lake yesterday took a couple of pals over to cowes for lunch and a beer!

I'm just curious what peoples thoughts are with running 90's and 115's on 5.4 Seariders? I was 3 up yesterday and fancied a touch more top end so I'm sniffing around at the moment for any advice or recommedations,

the 60 is good, I like to here what the increase is like from a 50/60 to the 90/115

THanks guys
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Old 28 July 2008, 05:04   #2
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What were you making 3 up with the 60?

I made 30 knots last year at WOT 3 up (nearly the weight of 4-I'm no lightweight!) with 17" pitch prop and 2 days worth of beer/camping kit aboard.
I think the biggest advantage is the improvement in acceleration. It makes the rough stuff a lot easier.

The 85 on mine seems undistinguishable from a 90.I'm still a power junkie and I can't see a lot of point in going up to 115-it doesn't seem worth it for the extra fuel consumption and a bit of extra top speed that'd rarely be used.
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Old 28 July 2008, 12:38   #3
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Hi Olly.

I had a 60 on mine when I first got it but upgraded to the current 90. Generally I pootle around at 20 - 24 kts and at those speeds I am actually using less fuel and oil than before as I am not running the engine hard. My top end with the 60 was about 26 kts and is now 37 kts. I know I could get more by changing prop to stainless etc but there are a LOT of rocks around here and if you hit them with an ally prop you damage the prop. Do the same thing with stainless and you damage your gearbox OUCH.

As far as the 115 issue goes. You would not be able to get insurance as this is beyond the manufacturers rating (also beware weight of 4 st engine). I expect the boat could easily handle it though as they have always been over engineered (if such a thing is possible).

Let us know what you decide.

Ian
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Old 28 July 2008, 13:07   #4
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Hi Olly,

I'd def go for a 90, you would not me the first person to upgrade...

not sure aboutt he 115. I have read lots of differing comments about the max rating and it leaves me confused... have seen a good few with the 115 on though. In the same way you would save fuel going to the 90, not sure it wold work that way going to a 115, as it seems quite a bit bigger of an engine visually, so like nos says, may be of little benefit. you're probably not going to be going more than 37kn ish with a 5.4 often anyway, so just comes down to doing it at lower revs, hence maybe saving cash on fuel..
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Old 28 July 2008, 16:46   #5
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I have just done some trials for the replacement engines for the MoD seariders. We only tried two engines, Mariner 75 Optimax and 90 Optimax. The 75 did just short of 38knts and the 90 did about 42knts. The 75hp running an 18" stainless and the 90hp running a 20" stainless prop. The 90 did get fairly twitchy and starts to chine dance alot so i would not advise a 115hp.

These figures vary from boat to boat as all the seariders seem to be slightly different and most of them are finished by hand, also most the MoD boats have had a hard life!!
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Old 28 July 2008, 17:20   #6
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Olly

A good friend, davybouy on here, runs a 5.4SR with a Tohatsu 90 EFI on.

It tops out at well over 40 knots and uses very little fuel in the process.
Its a very well balanced boat in the rough stuff and can only be described as a really good combination.

I'd be careful of over engining a 5.4. They are great boats, well balanced with something like a 80 or 90 on the back, and deliver a good top end etc.
A 115 could ruin the boat in all but top end performance, it may be too stern heavy and ruin the handling just to get those few extra knots.

As has already been said, something like a 80 or 90 should give you better fuel economy than your 60, as the engine will be running much lower down its rev range for a given cruising speed, yet you will have the option of going much faster when you feel like it, or you'll be able to maintain a given cruising speed with a heavier payload.

Davybouy and his 5.4 will be with us in Dartmouth next week if you fancy joining us for a couple of days to see how it goes.

Nasher.
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Old 29 July 2008, 06:03   #7
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Some good advice there thanks guys - My mate had a portable gps and it recorded 33mph as best speed so I guess around 28 knots mark, My main concern was like you're all saying a good cruising speed is what I want without really having WOT for prolonged periods, firstly due to engine stress and secondly fuel economy, I can't tell you the rpm as the rev counter is playing silly bugggers, I've tried it on all 3 pole settings and the needle just goes round round and stays there even at idle!

I think a 90 would best
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Old 29 July 2008, 23:42   #8
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Quote:
Originally Posted by ollyit View Post
Some good advice there thanks guys - My mate had a portable gps and it recorded 33mph as best speed so I guess around 28 knots mark, My main concern was like you're all saying a good cruising speed is what I want without really having WOT for prolonged periods, firstly due to engine stress and secondly fuel economy, I can't tell you the rpm as the rev counter is playing silly bugggers, I've tried it on all 3 pole settings and the needle just goes round round and stays there even at idle!

I think a 90 would best
ive run a 75 and 90. i like the 90 a little better, but its not THAT different, imo. also wot with a 90 ive run over 120 miles @ 4.4mpg. thats statute miles and gps.
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