having engine trouble with my 5.7 Mercruiser Horizon MPI.

[newbienewb]

hi all,
Some time ago (actually at the end of the previous aussie summer), i posted a thread about issues i was having with poor holeshot.

I parked the boat for winter, and have been running it around over the last week, and not only am i still having problems, things seem to be getting worse. Im hoping someone can help.

Boat is a 7M australian whittley cruisemaster. around the 2 ton mark - maybe a little more.

Engine is a 5.7 Mercruiser Horizon. I think around 2002 vintage. Fuel is cool fuel I, i believe. Compression test showed up no serious issues. One cylinder is slightly down, but nothing serious.

1) When cold (ie within about the first twenty minutes of starting) then engine seems to be slightly more responsive on holeshot. After that it seems to be quite sluggish on takeoff.

2) Any time i holeshot (regardless of hot or cold), i get terrible pinging from the engine. I have emptied all fuel and have refilled it with premium unleaded (98 octane). It still pings.

3) At full throttle on holeshot, I'm barely able to achieve about 2900 RPM. To me this seems very very low. Seems to lack a lot of horsepower. When up on the plane, if i push it hard, i will get about 4100rpm on a really flat water.

4) Just today, it has started "surging" quite badly. we were cruising along about 28 knots, and it just lost a whole lot of power. I backed right off, and it seemed to idle along fine, so i powered back up again and it seemed to be lacking even more power. Once i finally got out of the hole, and cruising at about 28-30 knots, it now has a notable surge.

5) As i was loading it on the trailer, i powered up slightly to help get up to the bow stop, and it seems that even ar around 1200 rpm it has a notable surge now as well.

So, im trying to think of what it could be. Im happy to spend money to fix it, but if possible would rather not throw good money after bad.

Fuel Pump?, Distributor? Something else?

Would really appreciate any ideas anyone can throw my way. Thanks so much guys. Much appreciated.

Dave

[shaungonemad]

Check your timing and your fuel pressure they should be the easiest things to check.

[newbienewb]

Thanks Sean. I have a fuel pressure tester at home so will check that when I get home from work tonight.

Does anyone know what the fuel pressure test should be?. I have been told 30psi at 1800 rpm.

Also timing?. Happy to read any documentation if anyone can point me in the right direction.

Thanks kindly

Dave


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[juggernaut]

You may get more of a response over on the clubsearay forum since mercruisers of all guises powered some sort of Sea Ray at some time.

[mal555]

With the holeshot issue, what is the pitch and diameter of the prop? Is the leg fully retracted down?
Fit a Stingray hydrofoil to the cavitation plate, these boats perform better with both holeshot and lateral trim once up on the plane with this low cost addition.
As a first call, change your fuel filter.
If propped correctly, you should be able to pull 4800 rpm at least, it sounds like she is over-propped and labouring hard.

[newbienewb]

With the holeshot issue, what is the pitch and diameter of the prop? Is the leg fully retracted down?
Fit a Stingray hydrofoil to the cavitation plate, these boats perform better with both holeshot and lateral trim once up on the plane with this low cost addition.
As a first call, change your fuel filter.
If propped correctly, you should be able to pull 4800 rpm at least, it sounds like she is over-propped and labouring hard.

Hi Mal,

Yep, the leg is fully down when attempting to get out of the hole.
Ill have to have a look into the hydrofoil - not exactly sure what that is!
I changed the fuel filter at the end of last season so I think that should be OK.
The sterndrive leg is a bravo three (twin prop), with 20P props on it. The ratio on the leg is 2.00. Im not sure if this is appropriate or not. Ive been trying to find a website that can help advise of correct prop pitch for my boat configuration.

@juggernaut - Thanks for that!. Ill head over there and see if anyone can help out.

Thanks guys - appreciate the help and advice.

[mal555]

Hi Mal,

Yep, the leg is fully down when attempting to get out of the hole.
Ill have to have a look into the hydrofoil - not exactly sure what that is!
I changed the fuel filter at the end of last season so I think that should be OK.
The sterndrive leg is a bravo three (twin prop), with 20P props on it. The ratio on the leg is 2.00. Im not sure if this is appropriate or not. Ive been trying to find a website that can help advise of correct prop pitch for my boat configuration.

@juggernaut - Thanks for that!. Ill head over there and see if anyone can help out.

Thanks guys - appreciate the help and advice.

image.jpg

The photo uploaded upside down for some reason, but there it is. There are a number of options, but these simple versions, Stingray Original, work great. This photo is not a Cruisemaster btw, just and example of the product.

just with the props, never just assume whoever fitted the props originally actually knew what they were doing as far as getting the combination correct

[brett62]

I just checked under my cruisemaster deck and found well over a 100 litres of water sitting in the hull and that's what I could see. If you haven't had a look down the inspection ports I would.

[brett62]

Dave I will also be putting the boat over a weigh bridge in a few weeks and I will let you know what the real weight of these hulls are. I have heard so many different weights for them and will be well over 2 ton I am sure. Start adding people, fuel,water and all the other crap we carry you will be 3 ton. mal555 would agree I think.

As with prop size I am running a bravo one drive same 5.7l 300hp engine and have a four bladed prop 14 1/4 x 17. I don't have any trouble getting out on the plane. Like Mal said you need to make sure your engine is getting it's rev range and you don't want it to take a life time to get there either. A mate has a SL 7m with the bravo 3 leg, not sure what prop size he is running and he has no trouble at all. The bravo 3 drive works well on these boats.

[newbienewb]

Hi Guys,

Mal - I found the Mercruiser prop tor tool on their website and filled that out to the best of my knowledge. It recommends a pitch of 24. Currently I have 20. If im understanding pitch correctly, a pitch of 20 should get me out of the hole easier than 24.

Ill have to have a look into the hydrofoil.

Brett - thanks very much for that. I think your feedback just further affirms my suspicions that my eninge seems really quite sluggish. What sort of RPM are you pulling on takeoff?

It will be very interesting to hear what the boat weighs in at when you put it on the weight bridge. Ive often eyed off the one at the BP on eastlink (Melbourne), but never actually stopped to follow through.

Where are the inspection ports you are talking about?. The only thing like that I can see are the two holes on the corners of the engine cover. But they simply feed into where the bilge is anyway. I suspect im missing something.

Thanks guys. Look forward to hearing back

Dave

[mal555]

Don't hesitate to call someone like Neville Whittley or their technical department if you need advice also, he has always seemed very approachable, chatty and quite genuine at boat shows previously.
I haven't had any experience with the Bravo III, so can't comment.

A "fully loaded" Cruisemaster will go to 3.5 tonnes on the trailer, maxed out with everything for a few days away, inflatable dinghy, small outboard etc., remember these boats have everything....including the kitchen sink

[brett62]

Dave inspection ports are a about in line with the back table mount. They give you access to your fresh water plumbing. Just need to roll the carpet back.

I hit the throttle to 4000rpm and that lifts me on to the plan in no time. I then back it off. I can get on the plan with out having to bring the leg all the way down also. I don't use the tabs at all until I am up and running and then I need to throw a little in due to the single screw throwing a chine down and this will change with speed.

Hi Guys,

Mal - I found the Mercruiser prop tor tool on their website and filled that out to the best of my knowledge. It recommends a pitch of 24. Currently I have 20. If im understanding pitch correctly, a pitch of 20 should get me out of the hole easier than 24.

Ill have to have a look into the hydrofoil.

Brett - thanks very much for that. I think your feedback just further affirms my suspicions that my eninge seems really quite sluggish. What sort of RPM are you pulling on takeoff?

It will be very interesting to hear what the boat weighs in at when you put it on the weight bridge. Ive often eyed off the one at the BP on eastlink (Melbourne), but never actually stopped to follow through.

Where are the inspection ports you are talking about?. The only thing like that I can see are the two holes on the corners of the engine cover. But they simply feed into where the bilge is anyway. I suspect im missing something.

Thanks guys. Look forward to hearing back

Dave

[newbienewb]

Wow....I can only dream of 4000 rpm on takeoff!!!!!. Lol. I can't even hit 3000.

Yeah I had a look in those inspection holes and dry as a bone .

Out of interest do you have a tender/dinghy on your roof?

I have Neville whittleys number here. Might give him a ring. Thanks for the reminder!
Cheers

Dave


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[brett62]

I had the tender on davits on the swim platform. It makes on difference getting on the plane. I only carry it and the outboard when I am heading off to the islands. I carry it on the rack if I am going a fair distance and still don't have trouble getting on the plane.

You certainly have an issue with the motor.

Glad you don't have the water problem I have.

[newbienewb]

Hi All,

just wanted to check in and give an update to this long standing issue.

Over the last four weeks or so ive been tinkering around changing a few things.

1) Fuel system pressure is fine.
2) New distributor cap and rotor button
3) Rewired all wires to distributor (very corroded)
4) cleaned injectors.

I took it out on the water the other weekend, and the good news is the surging (which I suspect was the corroded wires to the coil), and the pinging, are both gone. This is great news.

However, the lack of RPM on takeoff is still persistent.

On the boat I have myself, my wife and our three young kids. I have a days worth of food and fishing gear along with a full water tank, and full fuel tank (about 150 and 250 respectively I think). However I still only manage 2900 at WOT.,

Engine is 5.7 MPI Horizon with about 400 hours. Bravo three the dual 20P props and a 2.00 ratio on the drive.

Compression on each cylinder is about 190 PSI, with the exception of one which is down at around 160

Im looking for any suggestions as to why I may be having issues hitting a good RPM on takeoff. I feel as though im starting to break the back of all these issues, but this one is really bugging me. With another family on the boat I need ot ask people to move down the front for launch........................a little embarrassing.

Look forward to any replies.

Dave