Thoughts on boat power surge

 I had my newish boat out on the weekend  - 315 Searay with 8.2L freshwater cooled Merc. Planning a trip to GI so I filled up the tank from about half full. Hadn't been out for 6 weeks following shoulder surgery so I took it for a rip from Hillarys down to Scarborough, varying from cruising speed to WOT to clean the hull off a bit. On the way back I had it cruising and suddenly it powered down and then back up again. Did it another one or two times and then ran normally from there on.

Any ideas of what may have caused the issue? Just concerned if I'm planning a longer run. Maybe a bit of moisture or just some gunk going through the injectors? Any thoughts and suggestions appreciated.


Swompa's picture

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 Perhaps a bit of shit in the

Thu, 2021-01-21 12:20

 Perhaps a bit of shit in the fuel? When was it last run or is it brand new? 

Did the engine revs change or did it just get sluggish? 

 

davewillo's picture

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 That's what I was thinking

Thu, 2021-01-21 14:20

 That's what I was thinking mate. It hadn't had a run for 6 or 7 weeks.

The revs dropped but then almost immediately picked up again. After doing that a couple more times it cruised happily back to the marina. Dropped anchor off the beach and moved around a couple of times squidding with no issues. Just don't want to konk out halfway to GI. That outboard you sold me wouldn't be much use with a 4 tonne plus boat!

Swompa's picture

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 Haha! Mate I genuinely

Thu, 2021-01-21 16:22

 Haha! Mate I genuinely regret selling it!

Struggling to find a good light weight motor for the duck!

 

Swompa's picture

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 Haha! Mate I genuinely

Thu, 2021-01-21 16:22

 Haha! Mate I genuinely regret selling it!

Struggling to find a good light weight motor for the duck!

 

davewillo's picture

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 Because I didn't settle on

Thu, 2021-01-21 17:10

 Because I didn't settle on the boat until late October and had a shoulder reconstruction at the start of December, we haven't used it yet. Will fire it up this weekend ahead of hopefully getting away next week. Sure it'll suit us perfectly!

Jackalchub's picture

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 May not be of help as this

Thu, 2021-01-21 12:52

 May not be of help as this was a 200hp 4 stroke outboard issue.. But I had surge cutting out.. and ended up being a high resistance joint in battery isolator circuit.. Eventually failed and I lost trim/tilt - fixed it and surge problem solved. Theory was the joint would fail intermittently, not giving the computer enough juice to run. Didn't spit out any codes. 

Just a guess, I have zero experience with inboards 

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Check your fuel filters

Thu, 2021-01-21 14:57

There's a good chance they're full of crud. 8.2 litres of Mercury big block must be a thirsty beast!.

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pelagicyachts's picture

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Im thinking along the lines

Thu, 2021-01-21 15:00

Im thinking along the lines of Jackal, if it were fuel it wouldnt suddenly recover - it would be a splutterly fall and rise
- i had the same thing happen on my previous 200 series on corragations- turned out to be a cracked battery connector - drop in power and safety shiz kicks in

check your battery(s) condition and connections as a starting point

davewillo's picture

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 Thanks fellas. I'll check

Thu, 2021-01-21 15:13

 Thanks fellas. I'll check filters and battery connections. Thankfully lots of room to get around in the engine bay.

Yes it is pretty thirsty beast SF. Quoted at 60 LPH at 22 knots. Not planned as a fishing boat - more of a cruiser that I can fish from. I'll do whiting and squid runs and quite a bit of other stuff if we're at Rotto or GI. Doesn't work out to costly for a weekend away with the wife. 

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 If its got a racor 2020

Thu, 2021-01-21 15:49

 If its got a racor 2020 style cartridge filter  check the inlet side of the filter as well as the filters . There is a check valve ball and spring  on the inlet that can get clogged easily with a  small chunk of shit out of the fuel tank lines and restrict fuel getting into the filter housing. 

sea-kem's picture

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 Definite process of

Thu, 2021-01-21 16:06

 Definite process of elimination Dave, start with the simple stuff like fuel as Cruzy says above then move on to electrical. 

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davewillo's picture

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 Thanks Andy. I'll get into

Thu, 2021-01-21 17:13

 Thanks Andy. I'll get into it this weekend and look for the issue. Planning to get out on Monday so I've got time to resolve it hopefully.

sea-kem's picture

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 Hope you can mate. My

Thu, 2021-01-21 17:36

 Hope you can mate. My shoulder crapped itself again today after digging some footings. So bloody busy with work but will have to find time to get it looked at. 

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davewillo's picture

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 I had no choice Andy. I

Fri, 2021-01-22 16:16

 I had no choice Andy. I completely ruptured a rotator cuff tendon plus tore ligaments and the AC joint. Pain was terrible and a cortisone injection only gave me about 3 weeks relief. Still hurts but it's healing so that's okay.

sea-kem's picture

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 Bloody hell mate, let us

Tue, 2021-02-02 17:54

 Bloody hell mate, let us know how you go healing wise. 

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davewillo's picture

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 Still struggling with a lot

Tue, 2021-02-02 18:50

 Still struggling with a lot of pain Andy but that's normal apparently. So long as it works I don't mind!

davewillo's picture

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 So we went to GI but got

Tue, 2021-02-02 17:16

 So we went to GI but got chased away by the wind after 1 night.

Replaced the fuel filter and checked electrical connections and the problem still happened. At first it was only when going over 20 knots but on the way home I couldn't do more than 2,500 rpm or it kept happening. Long way to Hillarys when you can't get on the plane!

May be a dodgy tilt sender as that cuts revs to under 2,000 if it thinks the leg is up. Anyway I'm going to leave it to a mechanic who can use his computer to try and diagnose the problem.

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Date Joined: 04/03/13

I am aware of a similar issue

Thu, 2021-02-04 09:55

I am aware of a similar issue with merc digital throttles - unsure how to fix but could be the culprit.

Or

I have had a similar issue myself and the source of the problem was the fuel line from the tank to the filter which was perished on the inside (outside appeared fine). Simple and cheap to replace in the process of elimination.

 

davewillo's picture

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 Thanks Coyote for those

Thu, 2021-02-04 14:34

 Thanks Coyote for those suggestions. The more I can look at myself or the more suggestions I can give the mechanic the better. Either way should save some $$$

Bloody boats!

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 Have you checked fuel tank

Sat, 2021-02-06 15:38

 Have you checked fuel tank breather/ vent & hose?

 

Jackalchub's picture

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 If the lugs have lost

Sun, 2021-02-07 05:00

 If the lugs have lost tinning it will have issues.. it's amazing how good a connection can look.. (12v)  but still cause dramas. Sometimes bridging them out 1 at a time is the only way. Once again this is only information.. not assumption of cause. I'm still in hospital and very foggy from meds too. Good luck dave 

davewillo's picture

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 Thanks Jack and Moose. Hope

Mon, 2021-02-08 14:25

 Thanks Jack and Moose. Hope you're on the mend soon Jack. Those bloody painkillers they gave me when I got my shoulder done in December really messed with me. Hope you fare better!

I'm getting it looked at this week as I don't have the time myself and I still struggle in tight spaces with my shoulder. The mechanic also suggested that it could be perishing in the fuel line internally like Coyote_Dave did. I darined the filter again on Saturday and the fuel had black crap in in it so I definitely think it's fuel. I'll let you know what he comes back with.

Thanks again for all the advice fellas.

davewillo's picture

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 Okay an update after having

Mon, 2021-02-15 12:15

 Okay an update after having the mechanic look at it.

I got a full service done and a couple of small jobs but the likely issue was fuel. Unbeknown the me the filter I changed was the primary and there is a two-piece filter in the fuel module, which also cools the fuel prior to delivery. I could have found it I guess but the fact that it also connects to seawater would have made me a little nervous in case I stuffed it up. Plus ai wanted a full servous and idagnotic check.

Anyway the filters were full of sludge so he thought that would be the problem and it was. Took it out yesterday and ran like a dream!

Thanks for all the advice fellas!

sea-kem's picture

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 That's a good outcome Dave,

Mon, 2021-02-15 12:58

 That's a good outcome Dave, especially when the problem is obvious.

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Swompa's picture

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 Good to see it was

Mon, 2021-02-15 13:03

 Good to see it was relatively simple!

 

davewillo's picture

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 Yeah I'm pretty happy that

Mon, 2021-02-15 13:36

 Yeah I'm pretty happy that in a process of elimination it was found early!