MerCruiser 8.1 HO - first long trip, want to reduce "mechanicals" anxiety

M

mrsrobinson

Well-Known Member
Mar 9, 2006
7,704
Virginia
Boat Info
2001 380DA
Engines
Caterpillar 3126
I close on a boat with twin 2002 Mercruiser 8.1 HOs, 500 hours, V-Drives, this week. I plan to take it to a marina that's about 12 hours away. I'll be on the Chesapeake Bay for about half of that time. These engines are new to me, but I am not new to boating or servicing MerCruiser engines.

I want to make sure they are as ready as they can be for the long trip and reduce the potential mechanical failures. Oil/Filers have been changed and belts replaced by the seller. I plan to do the raw water impellers. Plugs looked good during compression checks.

Is there anything else I should do/check from a mechanicals service/maintenance point of view to feel as good as I can taking the trip? V-Drives, engines, etc.?
 
Fuel tank check? Stick for any water.
Take some spare fuel filters, the boat may not have seen the shaking the bay can cause in a while.
 
Every time I see your boat name I think about the tennis rackets I play with, Babolat :) And my late step dad was from Rock Hill, SC.
 
Opinions on spare parts stocking is just about as varied and passionate as the political opinions around here.

The most important thing you can carry is a Tow Boat US membership, in my humble opinion. Or SeaTow if they provide better coverage in your area.

Bring some oil. Check the oil. Bring some beer. Drink the beer. And enjoy the trip! You've got two engines. Just do your best to keep at least one running and you'll be absolutely fine :)
 
Stee6043 said:
Opinions on spare parts stocking is just about as varied and passionate as the political opinions around here.

The most important thing you can carry is a Tow Boat US membership, in my humble opinion. Or SeaTow if they provide better coverage in your area.

Bring some oil. Check the oil. Bring some beer. Drink the beer. And enjoy the trip! You've got two engines. Just do your best to keep at least one running and you'll be absolutely fine :)
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Agreed, agreed, agreed. I have limped back many a time on one engine.
 
Stee6043 said:
Opinions on spare parts stocking is just about as varied and passionate as the political opinions around here.

The most important thing you can carry is a Tow Boat US membership, in my humble opinion. Or SeaTow if they provide better coverage in your area.

Bring some oil. Check the oil. Bring some beer. Drink the beer. And enjoy the trip! You've got two engines. Just do your best to keep at least one running and you'll be absolutely fine :)
Click to expand...
Bring beer! Had a boat, bad carb, wouldn’t run over 1500 rpm. Buddy and me stocked cooler and left early for a 5 mile trip to mechanic. Took 5 glorious hours on smooth summer water, by time we arrived we were wasted. Good Times.
 
Pirate Lady said:
Bring beer! Had a boat, bad carb, wouldn’t run over 1500 rpm. Buddy and me stocked cooler and left early for a 5 mile trip to mechanic. Took 5 glorious hours on smooth summer water, by time we arrived we were wasted. Good Times.
Click to expand...
Haha, took me almost 7 hours get back from Washington, DC to Stafford, VA, in the dark, on one engine in my 2001 Monterey 302. That included a thunderstorm too. No drinking, luckily I was able to follow my GPS track. Lots of drinking when we got her docked though around 1AM.

I am not concerned about the river boating, it's the Bay and a "new to me" boat where I don't know her that well just yet.
 
Check the temps on the tops of the exhaust risers once the engine is warmed up. You should be able to keep your hand on them for a few seconds if there is adequate cooling flow through the system. One side will always be a little warmer than the other, but lack of flow can cause real issues. These are really robust engines, but without adequate cooling any engine can have issues.
 
Thanks, survey and sea trial is this thursday, I plan to take my digital laser infrared thermometer with me. Any idea what temperature I should be looking at on top of the risers?
 
Also do you know when the manifolds were last replaced? After 4-5 years you could have some major issues. You don’t want water getting into the engine.
 
Seller says 3-4 years ago (done by previous owner), but no receipt from previous owner. Boat appears to have been fresh water used only. No signs at all of barnacles on the running gear or signs of salt anywhere.
 
500 hours on a 2002 boat is pretty low hours but enough that it was being used. If it sat mostly in freshwater than I think you have it covered. The only thing I'd do is change the transmission fluids and check the filters.

I would assume that comment about the Previous Owner changed the manifolds but doesn't have the receipts is BS. No one on a boat spends $4000-6000 on a desirable maintenance item and doesn't keep the receipt.

Do you know if the Cool Fuel units were ever changed/upgraded? That's about the only 8.1 failure point. The symptoms will be a miss on the engine when increasing RPM's. Typically it'll still run fine at idle, or just above, so you'd get home no matter what.
 
I agree to the BS and even questioned the current owner/seller on it. My guess is he never asked/didn't know to ask and just said what he said to me to move the conversation forward. No way of really knowing unless one is pulled and inspected I guess.

I was informed by a mechanic the originals were aluminum and if they are cast iron now then they've been replaced. Is that correct?

I don't know about the cool fuel. I had these on my last 7.4s, never knew what they were, or that I had them, until the raw water hose clamp broke under power.
 
Plug wires can be a source of problems on these motors - I speak from experience.

Make sure the disc filter in the cool fuel module has been changed as this can be overlooked during servicing when changing the normal fuel filter. That is there are two fuel filters that should be changed per cool fuel module.

The IAC muffler in the 12 o clock position in the throttle body is also overlooked and can lead to the death of your IAC valve if it blocks. You need to remove the flame arrestor to change this.

Could dose your fuel with an additive for the trip - I use Starbrite Startron.
 
juggernaut1 said:
Plug wires can be a source of problems on these motors - I speak from experience.

Make sure the disc filter in the cool fuel module has been changed as this can be overlooked during servicing when changing the normal fuel filter. That is there are two fuel filters that should be changed per cool fuel module.

The IAC muffler in the 12 o clock position in the throttle body is also overlooked and can lead to the death of your IAC valve if it blocks. You need to remove the flame arrestor to change this.

Could dose your fuel with an additive for the trip - I use Starbrite Startron.
Click to expand...
juggernaut1 said:
Plug wires can be a source of problems on these motors - I speak from experience.

Make sure the disc filter in the cool fuel module has been changed as this can be overlooked during servicing when changing the normal fuel filter. That is there are two fuel filters that should be changed per cool fuel module.

The IAC muffler in the 12 o clock position in the throttle body is also overlooked and can lead to the death of your IAC valve if it blocks. You need to remove the flame arrestor to change this.

Could dose your fuel with an additive for the trip - I use Starbrite Startron.
Click to expand...
Good advise, thank you. I always used the Starbrite Startron in my previous boats.

Can you recommend a good replacement wire set?

Anyone know the part # for the IAC and IAC Muffler? And a reputable vendor to purchase them from? I'd like to have a spare IAC on the boat.

Same question for the fuel filter and disk. I have already purchased replacement/spare fuel/water separators.

What about the coil packs? Are they known to fail, and should I have a backup on the boat? I recently replaced them and the plugs in my BMW 335i so I am familiar with them.
 
I would have the manifolds inspected. They could be the originals, or maybe replaced when they switched from aluminum, but that would still be 10+ years. That’s an issue that could kill an engine on your first trip.
 
Who is Stee?

I agree w/having the manifolds inspected. However, if I am going to have each one pulled for inspection, and pay the labor, shouldn't I just go ahead and replace them?
 
Coil packs are generally reliable so no need to replace.

I currently have the equivalent Volvo 8.1 wires on my motors and subsequently picked up spare original Delco's sets from Michiganmotorz. If you use Michigan just make sure they are still selling the Delco's before purchasing.

All my other service items and manifolds are from my local Merc dealer. Nuwave Marine might be a good local source for you.
 
Dumb question, do all Mercs have cool fuel systems? I've never noticed one in the engine bay.
 
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