4-stroke cam belts

[Craig Killip]

Dear All,<br />We are going to look at a selection of boats this weekend. PLease could someone advise if all 4 strokes need a cam belt changing and if there is a set recommended life span - does this vary between manufacturers?<br /><br />Many thanks in advance.

 

[JB]

Re: 4-stroke cam belts

Howdy, Craig.<br /><br />Welcome to iboats. <br /><br />No, not all 4 strokes drive the cam(s) with belts. Some are gear driven (Suzuki/Johnson DF40 and DF50 for sure). Some may be chain driven, though I can't think of one at the moment.<br /><br />Most with belt driven cams recommend a replacement period somewhere in the hundreds of hours. I haven't heard of a belt failure in any 4 stroke outboard, though people pushing 2 strokes talk a lot about the possibility.<br /><br />Not a thing to worry about or base a purchase decision on.

 

[Craig Killip]

Re: 4-stroke cam belts

Excellent, thanks for the help JB - you're a star! You've helped me before with my outboard issues too! (lost my original user name!)<br /><br />That's great news, I was worried that they may need doing every 6 years like a car or similar.

 

[TOHATSU GURU]

Re: 4-stroke cam belts

Just a quick note about cam belts. I've spoken with some of the engineers in the past about them as to how long they will really last. They figure somewhere between 700 and 2000 hours The reason they have the low hour replacement schedule is to protect the manufacturer from liability lawsuits. IE Bubba has 1000 hours on a belt and gets stranded. Any time they can place a limit on a belt, impeller, propeller, etc., you can bet they will cover themselves.

 

[Craig Killip]

Re: 4-stroke cam belts

700 hours is still quite a lot for a recreational outboard though I would have thought. <br /><br />Well, reading the forum, if it's efi then that's the way to go!<br /><br />Fingers crossed for this weekend! I'll probably be back on here with all my problems for you!<br /><br />Thanks for the help!

 

[Silvertip]

Re: 4-stroke cam belts

Look at it this way -- four stroke engines are generally interference engines. That means if a timing belt breaks valves hit pistons. That makes holes in various places, bends valves and generally renders all the pieces useless. Nothing inherently wrong with a four stroke but don't ignore the timing belt. Your car rarely sees 6000 RPM but an outboard sees 5500 - 6000 RPM regularly. Check its tension and condition frequently.

 

[WillyBWright]

Re: 4-stroke cam belts

Certain powerheads are now non-interference. But on the 4-strokes I've seen, replacing that belt is no big deal. You certainly don't have to take a gazillion thingas apart to get to it like on a car. It's right out in the open.

 

[Silvertip]

Re: 4-stroke cam belts

At 6000 RPm any engine can become an interference engine. Some just moreso than others.

 

[BillP]

Re: 4-stroke cam belts

My 4s only says to "check" for "cracks". That could be age or hours. Regardless, like Willy says, my motor's belt is in the open, easy to eyeball and easy to change. But what that really means is more time to change crankcase oil and check/adjust valves. I'll still take a 2s without the extra mechanisms to deal with.